Procedures for Joint Preservation
A joint can potentially deteriorate for many reasons. The wear and tear of many years may be most common. In addition, infection can result in articular cartilage damage that then progresses over the years. Trauma may distort the joint, cause instability, or result in abnormal muscle forces, as occurs, for example, with a rotator cuff tear leading to cuff arthropathy. Other causes include (1) synovitis, as occurs, for example, with hemophilia, which forces the joint to dispose of blood on multiple occasions, and rheumatoid arthritis, which causes a proliferation of the synovium, which may destroy the articular cartilage; (2) osteonecrosis, which may result in fatigue fractures and collapse of the joint, with subsequent incongruity; and (3) abnormal distribution of load in the joint that results, for example, from malalignment. Certain procedures can slow progression of the deterioration resulting from these three causes and prolong the useful service of the joint. These procedures include synovectomy, core decompression, and osteotomy.
Synovectomy is a treatment that may prolong the life of the articular cartilage through removal of proliferative synovitis, which damages cartilage. Synovectomy is indicated for chronic but not acute synovitis. Chronic synovitis is a clinical entity characterized by proliferation of the synovium and may be monoarticular, as in pigmented villonodular synovitis, or polyarticular, as in rheumatoid arthritis or hemophilia. The term synovitis is relatively nonspecific, and the disorder is usually the result of a reaction to joint irritation.
Indications and Contraindications
The most common indication for synovectomy is rheumatoid arthritis, but the procedure may be beneficial in many other conditions, such as synovial osteochondromatosis, pigmented villonodular synovitis, and hemophilia, and occasionally following chronic or acute infection.
More specific indications for synovectomy include the following conditions:
Synovitis with disease limited to the synovial membrane with little or no involvement of the other structures of the joint
Recurrent hemarthroses in conditions such as pigmented villonodular synovitis or hemophilia
Infection when along with irrigation and debridement of the joint there is imminent destruction by lysosomal enzymes derived from white blood cells that may be liberated from the infection
Failure of conservative management
Contraindications include reduced ROM, significant degenerative arthrosis of the involved joint or other joint, or cartilage involvement.
Synovectomy is most commonly performed on the knee but also often on the elbow, ankle, and wrist. Three main techniques are available: open synovectomy, synovectomy with use of the arthroscope, and radiation synovectomy.
Open synovectomy is becoming less common because of pain that causes difficulty in obtaining full motion following surgery. Continuous passive motion may be beneficial in these cases. Open synovectomy may be necessary in cases of pigmented villonodular synovitis or synovial osteochondromatosis, although these diseases may also be treated by arthroscopy, which permits noninvasive complete removal of the synovium in many cases.
Synovectomy with Use of Arthroscope
Synovectomy with use of the arthroscope may be tedious, especially in large joints such as the knee, because complete treatment requires removal of the entire synovium in many cases.
A study of pigmented villonodular synovitis of the knee treated by total and partial arthroscopic synovectomy demonstrated that total synovectomy resulted in a low recurrence rate, whereas partial synovectomy resulted in symptomatic and functional improvement but a fairly high recurrence rate. Arthroscopic synovectomy was recommended only for localized lesions.
Radiation synovectomy is a technique that is becoming much more popular. It is used in knee joints affected by rheumatoid osteoarthritis. An injection of dysprosium-165-ferric hydroxide macroaggregates is given and leads to improvement in a significant percentage of patients. Proliferation of synovium decreases following this procedure, and there is less pain, blood loss, and expense than with more invasive procedures.
A similar technique is used in the knee joint in hemophiliacs. Phosphorus-32 chromic phosphate colloid is used and can be given on an outpatient basis. This is a safer technique for health care personnel, who have less contact with the blood of the hemophiliac patients, many of whom have become human immunodeficiency virus (HIV) positive through contaminated blood factor replacement.
Mendenhall WM, Mendenhall CM, Reith JD, et al: Pigmented villonodular synovitis. Am J Clin Oncol
Cartilage Repair Techniques
Defects of articular cartilage were long considered permanent injuries, and the irrevocable sequela was gradual deterioration over time. The treatment of cartilaginous diseases and injuries was limited by the slow and poorly understood metabolism of articular chondrocytes. Current cartilage repair procedures pertain only to focal full-thickness cartilage defects. Such injuries are typically found in young (<40 years) patients injured during athletic activities or in patients with osteochondritis dissecans. Cartilage repair techniques are contraindicated in smokers and patients with high BMI (>35 kg/m2), malalignment, meniscal deficiency, ligamentous laxity, or inflammatory conditions.
Because articular cartilage is avascular, prior surgical treatment consisted of chondroplasty, where underlying subchondral bone was either drilled, burred, or microfractured to produce bleeding and an inflammatory response. Although multiple growth factors may be released with bleeding, the ensuing repair tissue is essentially fibrous scar tissue with inferior load-bearing capabilities compared with articular cartilage. As a result, the repair tissue eventually degrades, leaving the defect little better than if left alone. Microfracture is still an option, primarily for smaller lesions.
Larger lesions (>4 cm2) can be treated with autologous or allograft cartilage transplant. Much enthusiasm followed autologous cartilage transplant in which viable articular chondrocytes are harvested from a patient with a focal cartilaginous defect and cultured in a laboratory. The population of chondrocytes is expanded and placed back in the patient at the site of the cartilage injury. The cells are held in place with a flap of periosteum sutured to surrounding healthy cartilage. Although encouraging early clinical results were reported with this method, similar results are shown using only the flap of periosteum, and recent analyses suggest that the evidence for the efficacy of this technique is inconclusive. Mosaicplasty is another method of dealing with small- to medium-sized focal defects of cartilage and includes transplantation of small osteochondral plugs of mature cartilage and bone from another region of the patient's joint. Small cylinders of cartilage and bone are removed from non–weight-bearing portions of cartilage and transplanted into focal femoral defects. Although encouraging short-term results are reported, whether the reconstructed cartilage endures remains to be seen. Larger lesions, such as those comprising an entire compartment of the knee, may be treated with bulk osteochondral allografts.
In contrast to these focal lesions, osteoarthritis with involvement of significant portions of a joint is a more prevalent affliction, affecting more than 40 million individuals in the United States. The early pathologic observations of osteoarthritis indicate structural degradation of the superficial layers of the cartilage architecture. Meaningful spontaneous repair of injuries limited to cartilage are not observed clinically, but a variety of experimental evidence suggests a latent ability to affect some degree of healing after injury and possibly in osteoarthritis. These suppositions include observation of increased DNA synthesis and proteoglycan synthesis in chondrocytes during intermediate stages of osteoarthritis. The procedures just described for cartilage repair do not apply for osteoarthritics when there is involvement of significant portions of a joint.
Bedi A, Feeley BT, Williams RJ 3rd: Management of articular cartilage defects of the knee. J Bone Joint Surg Am
Brittberg M, Lindahl A, Nilsson A, et al: Treatment of deep cartilage defects in the knee with autologous chondrocyte implantation. N Engl J Med
Gomoll AH, Farr J, Gillogly SD, et al: Surgical management of articular cartilage defects of the knee. J Bone Joint Surg
Vasiliadis HS, Wasiak J: Autologous chondrocyte implantation for full thickness articular cartilage defects of the knee. Cochrane Database Syst Rev
Core Decompression with or without Structural Bone Grafting
Indications and Contraindications
Core decompression with or without bone grafting is a surgical treatment primarily used for the femoral head because the hip is the joint most commonly affected by osteonecrosis. The knee and the shoulder are affected less commonly. Osteonecrosis results from loss of blood supply to the bone and is associated with a variety of conditions. Under repetitive stress, microfractures occur, are not repaired, and eventually lead to collapse of the necrotic bone and disruption of the joint surface.
Several factors have been examined as potentially predictive of progression in the patient with an asymptomatic osteonecrotic lesion of the femoral head. While lesion location, lesion stage, age, gender, and BMI have all been suspected as important, the size of the lesion, particularly when over one third of the size of the femoral head, is probably the most significant risk factor for progression.
The treatment of osteonecrosis is controversial because the outcome is frequently unsatisfactory. Spontaneous repair of the osteonecrotic lesion may occur but is an exception to the usual natural history of osteonecrosis. Core decompression, core decompression with electrical stimulation and bone grafting, and core decompression with structural bone grafting are considered acceptable forms of treatment for this disorder. Another treatment involves use of a free vascularized fibula transplant after core decompression.
The goal of core decompression is to alleviate hypertension in the bone caused by obstructed venous egress from the affected area. The theory is that drilling a hole in an involved bony area diminishes pressure and permits the ingrowth of new blood vessels, which allow repair of the avascular bone and prevent joint destruction. Corticocancellous bone grafting is considered an alternative to simple core decompression because some evidence indicates this would place the femoral head at less risk of collapse in the postoperative period before new bone formation can occur. Core decompression or structural bone grafting is indicated in early osteonecrosis prior to collapse of the femoral head (Ficat stage I or II).
Core decompression is usually performed on the hip but may also be done on the knee or the shoulder. A lateral approach is used for the hip, and a pin is placed into the osteonecrotic area under fluoroscopic control. A reamer or core device is then passed over the pin to achieve decompression, and a sample of bone may be obtained for pathologic analysis. If structural bone grafting is to be performed, the graft may be placed over the pin (allograft or autograft fibula). Again, placement is performed under direct radiograph control.
The results of core decompression are mixed, possibly as a result of differences in technique, lack of standardization of staging, and different etiologies of the osteonecrosis. The major complication of the procedure in the hip is fracture from torsional failure that results from the stress concentration site in the lateral aspect of the cortex. Reports of structural bone grafting by some investigators are highly favorable, with a high percentage of asymptomatic hips showing no evidence of progression of necrosis or collapse. One series reported a relatively high rate of postoperative or intraoperative fracture (four of 31 cases).
Osteotomy should be considered part of the armamentarium of the orthopedic surgeon in the treatment of biomechanical disorders of the knee and the hip. Osteotomy of the hip for osteoarthritis is less frequently performed than osteotomy of the knee. Abnormal distribution of load may be alleviated by osteotomy. Femoral head coverage may be improved with osteotomy of the pelvis, orientation of the femoral head may be improved with osteotomy of the proximal femur, and realignment of the load on the medial and lateral condyles of the tibia may be improved with osteotomy of the femur and/or the tibia. The most common procedure is high tibial osteotomy, sometimes referred to as Coventry osteotomy, which corrects varus malalignment of the knee by removal of a wedge of bone from the lateral side of the tibia. Other osteotomies are performed for residual deformity from healed fractures. These are tailored to the particular problem presented by the patient. Either intraarticular (ie, condylar osteotomy of the medial compartment [Figure 6–6]) or extraarticular osteotomies can be done to correct deformity.
An intraarticular osteotomy can be of benefit in tibial plateau fractures. A: Preoperative radiograph of an intracondylar fracture of the tibial plateau. B: Postoperative view after osteotomy of the lateral tibial condyle.
Alleviation of abnormal stress through high tibial osteotomy prevents osteoarthrosis or, alternatively, reduces pain caused by unicompartmental gonarthrosis. The procedure is indicated in relatively young (<55 years) patients who have unicompartmental degeneration with relative sparing of the patellofemoral joint. The knee should have a good ROM, preferably with no flexion contracture. The knee must be stable, with no demonstrated medial or lateral subluxation. The ideal patients are younger than 55 years, not obese, and wish to continue an active lifestyle, including activities such as skiing or tennis. Evaluation of the uninvolved compartment (either medial or lateral) may be accomplished by arthroscopy or with an MRI bone scan. The normal anatomic axis of 5–7 degrees (angle between the shaft of the femur and the shaft of the tibia) on the standing AP film must usually be overcorrected to 10 degrees. High tibial osteotomy is usually indicated for patients with medial gonarthrosis, although it can be performed in patients with a mild valgus malalignment (genu valgum) of less than 12 degrees. If malalignment is larger than this, it can be treated with a distal femoral supracondylar osteotomy. A high tibial osteotomy that results in a joint line that is not parallel to the ground indicates that the osteotomy should be performed through the distal femur. Lateral gonarthrosis from genu valgum is a relatively frequent result of lateral tibial plateau fractures, although rheumatoid osteoarthritis, rickets, and renal osteodystrophy may also produce this disorder.
A closing wedge proximal tibial osteotomy to treat varus malalignment is performed through a lateral hockey-stick incision or a straight lateral incision. Exposure of the lateral, anterior, and posterior aspects of the tibia is made, and a closing wedge osteotomy is performed. The proximal portion of this osteotomy is made parallel to the joint surface under image intensifier control (Figure 6–7). With the help of guide pins, the appropriate distal cut is made, as determined from preoperative standing radiographs, to provide the necessary correction, which in the average case is approximately 1 mm per degree of correction as measured on the lateral cortex. This technique should only be used to double-check previous calculations, however. Resection of the fibular head or the proximal tibiofibular joint allows correction of the valgus angle. Fixation can reliably be obtained with staples, and other commercial fixation devices are available. Care must be taken to avoid damage to the peroneal nerve. Medial opening wedge osteotomy is performed through a medial incision, using a plate to hold the correction. The opening wedge defect is bone grafted. Other problems that may be encountered include fracture of the proximal fragment or avascular necrosis of this fragment, which may occur if care is not exercised in performing the procedure. Preoperative planning and intraoperative navigation can aid in achieving appropriate alignment.
High tibial osteotomy, showing staples holding the osteotomy in place.
The results of high tibial osteotomy are not as predictable as unicompartmental knee replacement or total knee replacement. Although pain is relieved in a high percentage of patients, this relief deteriorates over time. Clinical reports indicate that approximately 65–85% of patients have a good result after 5 years. Results of series vary because of the differences in patient population, surgical technique, and preexisting pathologic factors. The procedure should be considered in a patient who wants to maintain a more active lifestyle and would be willing to accept the possibility of some pain or loss of pain relief over time.
Certain unusual conditions of the hip can be treated with osteotomy to prevent or retard coxarthrosis. These include osteochondritis dissecans and other traumatic conditions that produce localized damage to the surface of the hip. Various biomechanical theories are proposed regarding the benefit of osteotomy of the pelvis and hip in decreasing the load on the hip. Although the theoretical arguments may be correct, in practical terms, the two reasons for performing this procedure are (1) a normal viable cartilage surface is moved to the weight-bearing area where previously there was degenerated, thinned articular cartilage; and (2) the biomechanical loads on the joints that cause pain are reduced. These can be reduced either through alteration of moment arms for muscles or, alternatively, by releasing or weakening the muscles. Significantly lengthening or shortening a muscle reduces the force it can apply across a joint. In hip disorders, disease on one side of the hip joint cannot be addressed by an operation on the other side. For example, although it is tempting to use femoral osteotomy to treat acetabular dysplasia, only temporary relief may be obtained.
Treatment for Acetabular Dysplasia
Acetabular dysplasia as occurs in developmental dysplasia of the hip may be defined by the center edge angle. The normal center edge angle is 25–45 degrees; an angle of less than 20 degrees is definitely considered dysplastic (Figure 6–8). The anterior center edge angle can also demonstrate an acetabulum that is too open anteriorly; an angle of 17–20 degrees is considered the lower limit on the false profile view. There is also an increased acetabular index.
Anteroposterior pelvis film demonstrating the center edge angle.
In individuals with a mature skeleton, limited pelvic osteotomies such as the Salter innominate or shelf procedure are not appropriate. These measurements are probably best considered in a three-dimensional view with CT.
To improve coverage and hip biomechanics significantly, an acetabular-reorienting procedure that also permits medialization is ideal. The Wagner spherical osteotomy permits complete redirection of the acetabulum but does not permit medialization and is technically demanding. A triple osteotomy is useful in positioning the acetabulum but causes severe pelvic instability. The periacetabular osteotomy described by Ganz permits acetabular redirection and medialization but preserves the posterior column, minimizing instability.
Treatment of Femoral Disorders
Osteotomy of the femur can safely and reliably be performed in the intertrochanteric region, with the expectation of union. Osteotomy of the femoral neck is likely to compromise the blood supply to the femoral head as the deep branch of the medial femoral circumflex courses along the posterior aspect of the greater trochanter.
Intertrochanteric osteotomies of the femur of various types are described. The goal of osteotomy is removal of degenerated articular cartilage from the weight-bearing dome and replacement of it with more viable cartilage. This procedure may involve any of the three degrees of freedom: varus and valgus angle, internal and external rotation, and flexion and extension. It is necessary when planning these procedures to be sure the osteotomy will provide an adequate ROM for the patient. These osteotomies have usefulness in very specific cases for osteoarthrosis, but their usefulness for osteonecrosis is extremely limited in the United States.
Feeley BT, Gallo RA, Sherman S, et al: Management of osteoarthritis of the knee in the active patient. J Am Acad Orthop Surg
Heijens E, Kornherr P, Meister C: The role of navigation in high tibial osteotomy: a study of 50 patients. Orthopedics
Marker DR, Seyler TM, Ulrich SD, et al: Do modern techniques improve core decompression outcomes for hip osteonecrosis? Clin Orthop Relat Res
Mont MA, Zywiel MG, Marker DR, et al: The natural history of untreated asymptomatic osteonecrosis of the femoral head: a systematic literature review. J Bone Joint Surg Am
Santore RF, Turgeon TR, Phillips WF 3rd, et al: Pelvic and femoral osteotomy in the treatment of hip disease in the young adult. Instr Course Lect
Sherman C, Cabanela ME: Closing wedge osteotomy of the tibia and the femur in the treatment of gonarthrosis. Int Orthop
Sierra RJ, Trousdale RT, Ganz R, et al: Hip disease in the young active patient: evaluation and nonarthroplasty options. J Am Acad Orthop Surg
Van den Bekerom MP, Patt TW, Kleinhout MY, et al: Early complications after high tibial osteotomy: a comparison of two techniques. J Knee Surg
Joint Replacement Procedures
Hemiarthroplasty is the replacement of only one side of a diarthrodial joint. The procedure is indicated for displaced fractures of the femoral neck or four-part fractures of the humeral head, but there are other indications in adult reconstructive surgery. In both the shoulder and the hip, osteonecrosis may result in collapse of the humeral or femoral articulating surface, with sparing of the glenoid or acetabulum. In the hip, nonunion of the femoral neck after open reduction and internal fixation may also be an indication for endoprosthetic replacement. In either joint, pathologic fracture or tumor may be an indication. Contraindications include active infection, rheumatoid arthritis, and possibly the patient's age. Endoprosthetic replacement in a young individual is certain to result, with time, in destruction of the articular surface that contacts the prosthesis. This may, however, take many years, and the patient may have a serviceable joint in the intervening period.
The choice of prosthesis depends on factors such as life expectancy, cost, and physiologic demand. For the shoulder, a cemented prosthesis should probably be modular to permit conversion to total shoulder replacement at a later date without removal of the stem, should that become necessary. Similar concerns for the hip apply. The femoral head can be replaced with a unipolar or bipolar prosthesis. The bipolar prosthesis allows motion to occur between the acetabulum and the prosthesis, as well as between the prosthesis and the articulating surface of the metal femoral head. This articulation is metal or ceramic on plastic and certain to produce debris from wear that may be detrimental to the durability of the hip prosthesis. Selection of a monopolar prosthesis, however, must not compromise conversion of the hemiarthroplasty to a total hip arthroplasty, should this become necessary. Hemiarthroplasty of the hip has been shown to be preferable to a total hip replacement in cases of displaced, intracapsular femoral neck fracture. The operative technique is quite similar to that of total joint replacement for each joint. The main difference in the hip is that the capsule is usually repaired after hemiarthroplasty. A posterolateral approach is most commonly used in the hip, although an anterolateral approach may be preferred in a patient with associated mental problems that may limit postoperative cooperation. If the posterolateral approach is used in such patients, a knee immobilizer may be necessary to prevent hip flexion that might lead to dislocation.
Joint replacement surgery became a viable treatment for arthritic afflictions of joints when the low-friction hip arthroplasty was developed by Sir John Charnley in the 1960s. This procedure consisted of the articulation of a metal femoral head on an ultrahigh-molecular-weight polyethylene (UHMWPE) acetabular component, with both components fixed in place with acrylic cement (polymethylmethacrylate [PMMA]). The long-term results are quite satisfactory, and the concept is now applied to other joints with variable success. Knee replacement, shoulder replacement, and elbow replacement now have satisfactory results and are routine when the indications for surgery are appropriate. Other arthroplasties, such as the ankle, wrist, and first metatarsophalangeal joint, are less successful. In fairness, the application of technology to these joints is not at the level applied to other joints. Success of all arthroplasties depends on the skill of the surgeon, the surgeon's understanding of the basic biomechanics underlying the joint function, the design of the prosthesis, and the technical equipment used to insert the prosthesis.
The design of the prosthesis is an evolutionary process that depends on laboratory and clinical experience. Hip replacement surgery, performed often, is highly successful. Less frequently performed arthroplasties, such as elbow replacement, are associated with less clinical and laboratory experience.
The original Charnley total hip arthroplasty was a stainless steel femoral prosthesis with a small collar, a rectangular cross section, and a 22-mm femoral head. The acetabular component was a UHMWPE cup. Both components were cemented into place with acrylic bone cement. Since then, an entire industry has evolved to produce new designs for hip components, including different head sizes (22, 25, 25.4, 28, 32, 35, and 36 mm); different femoral component lengths (ranging from 110 to 160 mm for standard prostheses); different cross sections (square, round, oval, I-beam); a porous coating for bone ingrowth attachment; and metal backing for the acetabulum (cemented or porous coated). The two generic designs that evolved from experience with bone attachment technique are the porous ingrowth and cement fixation prostheses.
A variant of total hip replacement, hip surface replacement, was popularized in the 1980s, but there were problems with design, which resulted in a high failure rate and caused it to be withdrawn from the market. Those designs used a spherical metal shell cemented on the femoral side with a polyethylene (UHMWPE) shell cemented on the acetabular side. The impetus for surface replacement is preservation of bone stock and lower dislocation rate, which has encouraged their use in younger patients. With the advent of metal on metal bearings, surface replacement has again become an alternative to total hip replacement. The current designs use a cemented, spherical shell with a small stem on the femoral side and an ingrowth metal shell on the acetabular side. Early results have been promising, but one design has been pulled from the market due to wear problems.
The indications for hip arthroplasty are incapacitating arthritis of the hip combined with appropriate physical and radiographic findings. The historical data that justify consideration of hip replacement surgery include pain requiring medication stronger than aspirin, inability to walk more than a few blocks without stopping, pain following activity, pain that wakes the patient at night, difficulty with shoes and socks or foot care such as cutting nails, and difficulty in climbing stairs. It is good practice to use a clinical rating score to evaluate these historical data (Table 6–6).
Table 6–6. Harris Hip Evaluation (Modified). |Favorite Table|Download (.pdf)
Table 6–6. Harris Hip Evaluation (Modified).
I. Pain (44 possible)
A. None or ignores it
B. Slight, occasional, no compromise in activities
C. Mild pain, no effect on average activities, rarely moderate pain; with unusual activity may take aspirin
D. Moderate pain, tolerable, but makes concessions to pain; some limitation of ordinary activity or work; may require occasional pain medicine stronger than aspirin
E. Marked pain, serious limitation of activities
F. Totally disabled, crippled, pain in bed, bedridden
II. Function (47 possible)
A. Gait (33 possible)
b. Cane for long walks
c. Cane most of the time
d. One crutch
e. Two canes
f. Two crutches
g. Not able to walk (specify reason)
3. Distance walked
b. Six blocks
c. Two or three blocks
d. Indoors only
e. Bed and chair
B. Activities (14 possible)
a. Normally without using a railing
b. Normally using a railing
c. In any manner
d. Unable to do stairs
2. Shoes and socks
a. With ease
b. With difficulty
a. Comfortably in ordinary chair 1 hour
b. On a high chair for one-half hour
c. Unable to sit comfortably in any chair
4. Enter public transportation
|C. Range of Motion||R||L|
|D. Location of pain|
Physical examination typically demonstrates a limited ROM, pain at extremes of motion, a positive Trendelenburg test, a limp, and groin or anterior thigh pain with active straight leg raising.
Radiographs demonstrate loss of joint space and other findings consistent with the cause of the disorder. Noteworthy features requiring special considerations for surgery are dysplasia of the acetabulum, protrusio acetabuli, and proximal femoral deformity or the presence of metal implants from previous operations.
After consideration of the lifestyle requirements of the patient, the surgeon may suggest this procedure as a means of alleviating pain, which is the main indication for hip replacement surgery. Other reconstructive procedures should be considered, including arthrodesis, osteotomy, and hemiarthroplasty. When selecting a procedure, one should consider the patient's goals in terms of work and leisure activity. A young person who performs heavy labor and has unilateral traumatic arthritis may be best served by arthrodesis, unless a change to a more sedentary occupation is anticipated. A 50-year-old bank executive who does not ski, play tennis, or ride horses but does swim and bicycle will probably have the best results with hip arthroplasty.
A choice must be made between cemented and uncemented arthroplasty, with the uncemented acetabular component nearly universally indicated. Its advantages include a consistently pain-free result, long-lasting fixation, and modularity to permit latitude in selecting head size and acetabular polyethylene component offset designs. Its disadvantages include the need for metal backing of the polyethylene liner, which may increase wear, and the possibility of dissociation of the plastic component from the metal. A cemented acetabular component manufactured from UHMWPE is usually reserved for an individual with a life expectancy of 10 years or less. The indications for an uncemented femoral component vary with the surgeon but usually depend on the age of the patient and the quality of bone, with younger patients or patients with type A or B bone most likely to benefit from the porous-coated prosthesis. The surface replacement is an alternative to total hip replacement with a cemented femoral component and ingrowth acetabular component. Past problems with surface replacement and the reports of serum metal ion increases suggest caution in recommending this device.
Certain aspects of hip replacement surgery apply to all arthroplasty techniques, including cement technique and bone surface preparation.
The most common approach for total hip arthroplasty is the posterolateral approach. After administration of anesthesia and placement of a thromboembolic stocking and intermittent compression stocking on the unaffected limb, the patient is rolled into the lateral decubitus position, with the affected side superior. Draping should leave the entire leg free and extending above the iliac crest. Kidney rests are used to support the pelvis at the pubis and the sacrum, and bony prominences should be protected. The incision is outlined on the skin before the skin is completely covered with an adhesive drape. By flexing the hip to 45 degrees, the incision can be made in line with the femur from approximately 10 cm proximal to the tip of the trochanter to 10 cm distal to the tip of the trochanter.
Alternatively, with the hip in the extended position, the incision is made from 10 cm distal to the tip of the trochanter extending proximally along the line of the trochanter and then curving posteriorly at approximately a 45-degree angle for another 10 cm. The incision is deepened to show the fascia lata and the gluteus maximus. An incision is made in the fascia lata directly lateral and extended proximally into the gluteus maximus, which is split in line with its fibers. A Charnley retractor is placed, and fat overlying the external rotators is removed. After putting the femur into internal rotation, the external rotators (piriformis, gemelli, obturator internus, and quadratus femoris) are tagged with sutures for reattachment and removed from their attachments at the trochanter. The gluteus minimus is separated from the capsule and preserved and protected, and a capsulectomy is performed. Alternatively, portions of the posterior capsule can be reflected for later reattachment. If the patient is not paralyzed with nondepolarizing muscle relaxant agents, excision of the capsule with electrocautery signals whether the sciatic nerve is particularly closely applied to the posterior of the acetabulum. The sciatic nerve must be identified and protected throughout the procedure if there is electrical transmission. Internal rotation of the flexed hip dislocates the hip, and the femoral head is delivered into the operative field. Using an appropriate template, the femoral head is resected with an oscillating saw. The femur is then externally rotated, and Taylor retractors are placed anteriorly and posteriorly to permit visualization of the acetabulum. The acetabulum is medialized, if appropriate, when medial osteophytes are present. Anterior osteophytes, if present, are removed under direct visualization. Reaming of the acetabulum is performed until a good bed of bleeding subchondral bone is obtained; progressive reamers are usually used. At this point, techniques diverge based on whether a cemented or an uncemented cup is used.
If a cemented cup is used, multiple holes with a diameter of 1/4–3/8 in are drilled in the acetabulum to provide firm cement interdigitation. One of the commercially available techniques that prevents bottoming out of the acetabular cup should be used, so the medial cement mantle will be adequate. The position of the cup is determined with trials, using the native acetabulum for guidance and radiograph if there is any concern about positioning. The cup is cemented into place after the acetabular bone is prepared with pulsatile lavage, epinephrine-soaked sponges, and pressurization of the cement.
If an uncemented cup is used, reaming progresses to a diameter 1–2 mm smaller than the actual size of the cup to be implanted. The cup is impacted into place, ensuring appropriate positioning. Fixation is achieved with screws or pegs, as specified by the manufacturer. A trial plastic component is inserted, and attention is returned to the femur.
The hip is internally rotated, flexed to approximately 80 degrees, and adducted, so the cut femoral neck is presented to the surgeon. Homan retractors may be used to help elevate the amputated femoral neck into the wound. A box chisel is then used to remove the femoral neck laterally. The canal is broached with a curet to provide an indication of the direction of the intramedullary canal. The femoral canal is then broached with increasing sizes of broaches, until all weak cancellous bone is removed. The prosthesis size is determined, and a cement restrictor is placed 2 cm distal to the final position of the stem tip. The canal is prepared for cementing with pulsatile lavage, medullary canal brushing, and sponges soaked with hydrogen peroxide or epinephrine. The cement is prepared and centrifuged or vacuum mixed and inserted into the femoral canal with a cement gun. The cement is pressurized, and the prosthesis is inserted into appropriate anteversion (approximately 10 degrees) and held in position until the cement cures. When the appropriate broach, as indicated by preoperative templating, is reached, a trial femoral prosthesis is inserted, the neck length is checked, and the prosthesis is reduced into position. ROM is tested at 90 degrees of flexion and should be stable to 40–45 degrees of internal rotation. External rotation to 40 degrees in the fully extended position must be obtained without impingement on the femoral neck posteriorly. Proper myofascial tension is assessed by telescoping the hip at 45 degrees (approximately 3 or 4 mm). Proper leg length is usually achieved when the rectus femoris tightness (flexion of the knee with the hip extended) is similar to prior to surgery. A further check on leg lengths can be made by comparing the center of the femoral head preoperatively with the proximal tip of the trochanter to trochanter-prosthesis center distance with the prosthesis in place. Measuring devices are designed to measure leg lengths, but up to 1 cm of discrepancy can still occur. An extended lip on the UHMWPE component may provide additional stability but may form a fulcrum on which the head may be levered out. The prosthesis trial is removed, and the permanent polyethylene component is put into place in the acetabular metallic shell. The femoral canal is then prepared for cementing.
After the cement hardens, a trial femoral head is used to put the hip through a second ROM. The optimal neck length is selected, and the appropriate prosthetic component is impacted into place. When combining modular components held together with a Morse-type taper, the manufacturers' components should not be mixed. The bore in the femoral head is placed on the trunnion and twisted and impacted into place with several sharp blows. The acetabulum is cleaned of debris, the femoral head is reduced, and the wound is closed. The external rotators are reattached with sutures placed through bone while the hip is in external rotation and abduction. The fascia is closed with interrupted sutures.
The design and insertion technique of the uncemented femoral components are somewhat variable and therefore are not described here, but a typical anatomic design uncemented hip is shown in Figure 6–9. This type of stem is inserted after reaming and broaching to size.
Radiograph of a standard design cemented arthroplasty with Co/Cr-polyethylene bearing surface.
Abbreviated mini incisions for the posterolateral approach to the hip are described. These generally use a small portion of the routine incision but are carefully placed to optimize visualization of the hip. One such technique places the incision posterior to the trochanter, about 8–10 cm in total length, with 4–5 cm proximal to the tip and 4–5 cm distal to the tip of the trochanter. This technique is becoming more prevalent among surgeons.
The lateral approach to the hip is performed with a trochanteric osteotomy after the fascia of the tensor fascia lata and gluteus maximus are entered. The patient may be in the supine position with a bump under the hip or in the lateral position. Prior to osteotomy, the trochanter is mobilized, and the trochanteric osteotomy is performed with an osteotome or a Gigli saw. The gluteus minimus is peeled off the capsule as the trochanter is mobilized proximally. After capsulectomy, the femoral head is dislocated anteriorly. The procedure is essentially identical from this point on until the trochanter is reattached. Various modifications of trochanteric osteotomy techniques are described. The abductor mechanism is extremely important in preserving the stability of the hip as well as the gait. Thus, extreme care must be taken to reattach the trochanter when the procedure is completed, so reliable union is achieved. Even in the best of hands, approximately one in 20 trochanters fails to unite, although the number of people who have disability or pain from a fibrous union is much lower. If wires are used to reattach the trochanter, they should be biocompatible with the prosthetic component, and a minimum of three should be used to achieve adequate fixation.
Trochanteric osteotomy is seldom used except for anatomic variations such as previous fracture that make other approaches difficult.
Anterolateral Approach (Watson-Jones Approach)
The interval between the gluteus medius muscle and the tensor fascia lata is used proximally to gain access to the femoral neck and hip joint. The patient is in the supine position, with a bump under the buttock. The skin incision follows the shaft of the femur distally and curves slightly anteriorly proximally. The fascia is incised in line with the skin incision and proximally splits the interval between the tensor fascia lata and the gluteus medius. The tensor fascia lata is then retracted anteriorly, and the gluteus medius is retracted superiorly and laterally. Because the fibers of the gluteus medius and minimus tend to run anteriorly, particularly in the osteoarthritic hip with destruction and shortening, these fibers must be released to provide access to the hip joint. The hip is externally rotated. The anterior capsule is incised, and the hip joint can then be dislocated. Osteotomy of the femoral neck proceeds at the appropriate level. Capsulotomy is performed, retractors are placed to provide acetabular exposure, and hip replacement is performed. The femur during this procedure is externally rotated. Care must be taken in exposing the acetabulum to prevent damage to the femoral nerve and femoral muscles.
Other Approaches and Techniques
Many variations of standard approaches are used for hip replacement including minimally invasive anterior, posterior, and anterolateral, with proponents espousing the benefits of each technique. The anterior, between the tensor fascia lata and sartorius muscles, and anterolateral approaches seem to offer the advantages of lower dislocation rate and ease of obtaining correct leg length. However, lateral femoral cutaneous nerve palsies are a problem. The posterior approaches may have a higher dislocation rate. Satisfactory results can be obtained with any approach in the hands of an experienced surgeon. Data have shown that proper prosthetic placement, especially the acetabular component, is critical to long-term survival of the implant. This is particularly true for ceramic-on-ceramic and metal-on-metal bearing surfaces. To achieve optimal placement of components, computer-aided surgical navigation has become available and is being used on a trial basis by many surgeons. These techniques can significantly lengthen surgical times, require additional or extended incisions, and increase costs as a balance to the gains in accuracy.
The two basic types of total hip replacement are cemented and uncemented. The bearing surfaces for both are the same, either cobalt chromium alloy, ceramic (alumina or zirconia), or an oxidized zirconium surface (which is chemically a ceramic zirconia surface), articulating with a UHMWPE bearing surface. The femoral stem replacement may be cobalt chromium or titanium alloy, either of which is also used for the metal backing of the acetabulum. Titanium is poorly suited to cemented applications in hip arthroplasty because it is less stiff than cobalt-chrome (and stainless steel), and therefore transmits greater stresses to the cement column.
The femoral component should be designed to provide intrinsic torsional stability without having sharp edges that would create stress concentration sites in the bone cement. A matte surface should be created to allow some mechanical interlocking with the cement, although currently this is controversial, and some surgeons recommend a polished surface. Adequate offset is necessary to restore the mechanical advantage of the abductors.
The choice of material for the femoral head is a trade-off between cost and theoretical advantages. The harder, wettable surface of ceramic heads theoretically results in less production of debris from wear and longer service of the hip replacement without loosening, but the cost is two to three times that of an equivalent-sized cobalt chromium (Co/Cr) head. The ceramic head also has a small chance of fracture, which can have significant ramifications for the patient, requiring another surgical procedure to correct the problem. Thus, in most individuals undergoing total hip arthroplasty, a Co/Cr head is probably optimal. In younger patients, the increased cost of a ceramic head may be warranted. At a higher cost than the Co/Cr, but lower than the ceramic femoral head, is the oxidized zirconium head which will not fracture, but may offer the advantages of lower wear. Femoral heads are available now in 22-, 26-, 28-, 32-, and 36-mm sizes. One clinical investigation of total hip replacements showed that 26- and 28-mm heads are associated with the least amount of linear and volumetric wear. A head of 22 mm may be necessary for patients with smaller acetabular sockets to provide adequate thickness of the polyethylene bearing surface. A minimum of 6 mm, preferably 8 mm or more, is suggested to lower the contact stress on the polyethylene and thereby reduce wear.
New bearing surfaces for the articulation of the hip joint are becoming popular. The possibilities include ceramic on ceramic (COC), Co/Cr on Co/Cr (metal on metal [MOM]), and ceramic or Co/Cr on radiation cross-linked polyethylene. The COC and MOM couples have been shown to be very sensitive to surgical placement of the acetabular component. More verticality of the cup can lead to higher wear, and squeaking of the bearing surface has been seen in a significant percentage of cases, a higher rate in COC than MOM. The impetus for this change is the possibility of lower wear debris. These articulation couples require long-term follow-up to determine if they will live up to their promise.
No evidence justifies use of a metal backing on the cemented acetabular component. Other design considerations to avoid are deep grooves that might evolve into cracks in the PMMA. The surface must be rough enough to allow the cup to bond to the cement through mechanical interlock.
Uncemented acetabular components have a spherical outer surface with at least one hole to permit the surgeon to determine if the prosthesis is fully impacted into place. The shell should have a minimum of 3 mm of metal to reduce the risk of fatigue failure. Cobalt chromium alloy or titanium alloy appears to be equally efficacious. The inner surface should lock the polyethylene in some fashion to reliably limit rotation and dissociation. The inner surface should be the mate of the polyethylene outer surface to reduce the chance of cold flow of the plastic as well as wear from relative motion. Recommended materials are listed in Table 6–7.
Table 6–7. Preferred Materials for Total Hip Replacement. |Favorite Table|Download (.pdf)
Table 6–7. Preferred Materials for Total Hip Replacement.
Uncemented femoral component
Cobalt chromium alloy
Cemented femoral component
Cobalt chromium alloy (forged)
Cast cobalt chromium alloy, titanium alloy
Cobalt chromium alloy
Zirconia, alumina, oxidized zirconium alloy
Cemented acetabulum bearing surface
UHMWPE component (no metal backing)
Metal shell with UHMWPE liner (revision)
Uncemented acetabulum bearing surface
UHMWPE with metal ingrowth outer shell
Ceramic or metal bearing surface with ingrowth outer shell
Titanium alloy, cobalt chromium
surface for acetabular shell
Cobalt chromium alloy
Design considerations for the uncemented femoral component are unclear at present. Use of porous coating, hydroxyapatite, or tricalcium phosphate coating is driven by manufacturing concerns and prosthesis strength requirements rather than an understanding of the biologic principles of hip replacement. Three design factors are important: (1) If a prosthesis is excessively stiff in relation to the bone to which it is attached, proximal osteopenia may result from “stress shielding” or “stress bypassing” of the bone; (2) approximately anatomic shape is appropriate to maximize the bone–prosthesis contact and reduce contact stress; and (3) stiffer prostheses seem to be associated with more pain in the thigh. Therefore, strategies to reduce stiffness seem appropriate. These factors are addressed by using titanium alloy as opposed to cobalt chromium alloy, but other factors may surface to affect this choice. Creating slots or grooves to reduce the torsional and bending stiffness also seems to be effective in reducing stiffness and resulting thigh pain.
Any major surgery is associated with a certain incidence of complications, which is certainly true for total hip arthroplasty. The surgeon must recognize these complications in a timely manner and treat them appropriately. The most common complications include deep venous thrombosis (DVT), fracture or perforation of the femoral shaft, infection, instability (dislocation), heterotopic bone formation, and nerve palsies.
Although some morbidity results from DVT, the real risk is pulmonary embolism, which is occasionally fatal. The incidence of DVT is high, but the incidence of fatal pulmonary emboli fortunately is low, in the range of 0.3%. The high incidence of DVT during hip replacement surgery is related to femoral vein damage from manipulation or retraction, intraoperative or postoperative venous stasis caused by immobility and limb swelling, and a hypercoagulable state directly resulting from the surgical trauma to the patient. Certain factors are recognized as predisposing the patient to higher risk for DVT, including a prior history of pulmonary embolus, estrogen treatment, preexisting cancer, older (>60 years) age of the patient, and length of the operative procedure, one factor that is under the surgeon's control.
Pharmacologic and mechanical measures are used to reduce the risk of DVT. The American College of Chest Physicians recommends at least 10 days of pharmacologic prophylaxis with low-molecular-weight heparin, fondaparinux, or warfarin. Recently, the U.S. Food and Drug Administration (FDA) approved rivaroxaban, an oral thrombin inhibitor, for DVT prophylaxis, which may become a standard for DVT prophylaxis. The National Institutes of Health Consensus Conference concluded that mechanical measures such as intermittent pneumatic compression (IPC) provide adequate prophylaxis for patients who are mobilized quickly, whereas anticoagulation therapy is recommended for those expected to undergo prolonged bed rest. Recent studies suggest that adequate mechanical measures may be used for postoperative prophylaxis, which is accomplished with a portable IPC device. Because DVT can lead to a catastrophic outcome, preventive measures are indicated starting in the presurgical area. The patient should wear an antiembolic stocking on the unaffected extremity, and both extremities can be treated with intermittent pneumatic compression during the operative procedure. Following surgery, a low-molecular-weight heparin (enoxaparin or dalteparin) is the treatment of choice. Patients who develop pulmonary embolus should receive routine treatment with heparin followed by warfarin.
Three degrees of nerve injury are recognized. In order of increasing severity, these are neurapraxia, in which conduction is disrupted; axonotmesis, in which the neuron is affected but not the myelin sheath; and neurotmesis, in which the nerve is completely disrupted, as in laceration. In total hip arthroplasty, the most common injuries are neurapraxia and axonotmesis. Neurotmesis is unlikely to occur, except when severe scar tissue predisposes the nerve to laceration. Early nerve recovery (days to weeks) indicates neurapraxia; while longer recovery (months) indicates axonotmesis.
Nerve palsies after total hip arthroplasty are relatively infrequent, but the incidence increases as the complexity of the surgical procedure increases. The sciatic nerve is most commonly involved, with the peroneal division of the sciatic nerve at the greatest risk (80% of cases). The femoral nerve is involved less frequently. An early study indicated an overall prevalence of 1.7%, with total hip arthroplasty for congenital hip dysplasia having a rate of 5.2% and for osteoarthrosis 1%, but a subsequent review suggested that the overall rate of palsy was reduced to approximately 1%. Revision surgery was associated with a rate of 3.2%. The type of injury most likely to produce nerve palsy is stretching or compression, although other mechanisms, such as ischemia, intraneural hemorrhage, dislocation of the femoral component, and cement extrusion, are also suggested as causes.
Nerve injury may be prevented by identifying high-risk cases, protecting the sciatic nerve from compression, and evaluating the sciatic nerve for possible stretching before the wound is closed. Stretching the sciatic nerve by as little as 2 cm increases the risk of palsy significantly. Palpation of the sciatic nerve for tautness with the hip and knee extended and with the hip flexed and knee extended (straight leg raising test) indicates whether there is danger of stretching the sciatic nerve. Shortening the femoral neck is one means of addressing this problem. If any doubt exists about whether stretching occurred, the patient should be placed in the hospital bed following operation with the hip extended and the knee flexed to relieve tension of the nerve, until the patient is awake and function of the nerve can be monitored.
Management of nerve palsy is generally conservative, with observation when the nerve is known to be in continuity and not stretched. Electromyograms and nerve conduction studies may be helpful but may not show changes until 3 weeks after injury. Recovery of some motor function in the hospital heralds a good prognosis, and if complete return is to occur, it does so by 21 months, according to one study.
Significant vascular complications are reported to occur in approximately 0.25% of total hip replacements. These may be caused by placement of retractors and acetabular screws (the safest screw location is in the anterior and superior quadrant of the acetabulum) and by damage to atherosclerotic vessels. Early recognition is important in these injuries.
The typical fracture associated with total hip arthroplasty involves the femoral shaft, but other fractures do occur. Fatigue fractures of structures such as the pubic ramus may occur following increased activity after hip replacement relieves pain. The intraoperative problem of fracture or perforation of the femur is relatively uncommon in primary arthroplasty. Perforation may occur in disorders such as sickle cell anemia and osteopetrosis or following previous internal fixation. These conditions may have resulted in sclerotic bone, which may direct the broach astray. Perforations are relatively easily managed by extending the prosthesis past the area of perforation. This distance is generally considered to be two femoral diameters for a perforation with a cemented arthroplasty, but longer distances may be necessary with uncemented arthroplasties, depending on the size of the perforation. An alternative is to use a structural allograft held in place with cerclage wires. In either case, cancellous bone grafting is prudent to facilitate healing.
After total hip arthroplasty, the stress state of the bone is definitely changed, and there is a stress concentration area at the tip of the prosthesis. Fractures in the periprosthetic area are relatively common. These fractures are classified as type A, involving the greater or lesser trochanter; type B1, B2, B3, around or just below the stem, with the stem well fixed (B1), stem loose (B2), or poor bone stock in the proximal femur (B3); or type C, well below the stem. Type A fractures are treated nonoperatively unless the cause is osteolysis, which may predispose the femur to more serious injury. Type B and C fractures are generally treated surgically. Revision is usually the treatment of choice if the prosthesis demonstrates loosening on plain radiographs. Bone grafting is generally necessary with bone deficiencies, and bicortical onlay grafting techniques may be necessary with poor bone stock. Open reduction and internal fixation may be indicated if the prosthesis is tight (types B1 and C), but generous bone grafting and careful observation are necessary to ensure healing. Fracture fixation devices applied in the vicinity of the femoral component may be tenuous, and these devices must not compromise the integrity of the cement mantle or prosthesis.
Dislocation Following Total Hip Arthroplasty
The incidence of dislocation following total hip arthroplasty varies somewhat from series to series, but ranges from 1% to 8% and averages 2–2.5%. Several factors are associated with higher rates of dislocation, including female sex of the patient and nonunion of the trochanteric osteotomy, revision surgery, and use of the posterior approach. Dislocation after revision surgery in one series was 10% after the first revision and 26.7% after two or more revisions. An ununited trochanter after revision was associated with a 25% rate of dislocation.
Factors important in preventing dislocation are proper placement of components, adjustment of myofascial tension, component design, and patient compliance. Variables found to have no statistically significant effect on the dislocation rate include the ROM of the hip and the femoral head size. However, a 32-mm head has a theoretic advantage over a 28-mm head because a neck of the same diameter would impinge earlier with a 28-mm head and when dislocation is a concern, larger heads are generally recommended, especially in revision situations. At the time of surgery, the myofascial tension is tested by traction on the femur. Displacement of 1 cm or more suggests an increased probability of dislocation after surgery.
The risk of dislocation after total hip arthroplasty diminishes as time passes without dislocation. A first dislocation often occurs within 6 weeks following surgery and is frequently a result of patient noncompliance with postsurgical guidelines. For a first dislocation, closed reduction is used, and careful assessment of the cause of dislocation should be made. If component position appears to be adequate, bracing for 3 months is recommended, along with careful explanation of hip dislocation precautions to the patient. Alternatively, removal of the acetabular component with replacement by a bipolar into the reamed acetabulum may be the best salvage procedure. Recurrent dislocation should be examined carefully for cause, with radiographs taken to evaluate the abduction and anteversion of the cup as well as the anteversion of the femoral head (Figure 6–10). Examination under fluoroscopy may reveal impingements, and push-and-pull films may reveal inadequate myofascial tension.
Approximate determination of the abduction-adduction angle and angle of anteversion of the cup. Exact measurement requires careful control of the direction of the x-ray beam.
After careful evaluation of the cause(s) of dislocation, surgical correction may be undertaken. Possible solutions include reorienting the offset lip of the acetabulum, changing the anteversion or abduction of the acetabulum, changing the anteversion of the femoral component, or advancing the trochanter to tighten the muscle envelope. Failure of these methods may require the use of a constrained acetabulum to prevent dislocation. This treatment should be considered a last resort because the reduced ROM resulting from the design of these cups can predispose the patient to dislocation as a result of levering out of the cup from neck impingement. Long-term bracing is a possible solution for recurrent dislocation in a patient with limited goals for activity. Recurrent dislocation causes significant anxiety, which encourages patients to seek surgical correction. The recurrence rate in such patients is as high as 20% after surgical correction.
During hip replacement surgery, an attempt is made to maintain or correct the preoperative length of the affected leg, so it is equal to the unaffected leg. This goal, however, is sometimes incompatible with (and therefore subservient to) myofascial tension in the ligamentously lax individual. Excessive lengthening is a potential cause of damage to nerve or vascular structures. Computer-assisted navigation or intraoperative radiography offers the best opportunity to achieve equal leg lengths, although other intraoperative measurement systems can be used. None are fail-safe. Hence, most surgeons advise their patients that the leg may be longer or shorter than normal after operation.
The rate of trochanteric nonunion after a primary total hip arthroplasty was approximately 5%, but trochanteric osteotomy is now seldom used in primary hip replacement. The percentage of patients who develop symptoms from this complication is smaller. Usually, migration of less than 1 cm is not associated with functional symptoms or pain.
The rate of nonunion after revision surgery is much higher, as much as 40%, particularly if there has been nonunion following the primary procedure. Diminished function, as evidenced by weakness in abduction and a limp that cannot be compensated for with a cane, is an indication for an attempt at reattachment of the trochanter. The surfaces should be freshened and rigidly fixed together; bone grafting may be necessary. Subperiosteal release of the iliac wing muscles may be necessary to allow the trochanter to be reattached to the femur.
Pain after trochanteric nonunion may be the result of a painful pseudoarthrosis or, alternatively, of fixation wires that may form a painful bursa.
The incidence of significant heterotopic ossification after total hip arthroplasty is 5% or 10%, although it is present to a lesser degree in perhaps 80% of patients. Definite risk factors include previous heterotopic ossification, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis or spinal ostosis (Forestier disease), unlimited hip motion preoperatively, head injury, and male sex of the patient. Other possible risk factors include trochanteric osteotomy, interoperative fracture, bone grafting, or localized muscle damage or hematoma.
Heterotopic bone is classified by either the Brooker or the Mayo classification (Table 6–8). Patients identified as being at risk for heterotopic ossification should undergo prophylactic treatment, careful surgical treatment, wound drainage, and irrigation of the wound prior to closing. In patients at risk, low-dose radiation, 6–8 cGy within a 1 day before surgery or the first 3 days after surgery, prevents grade 3 or 4 heterotopic ossification. Indomethacin given postoperatively for 7–21 days is effective, although it may be poorly tolerated by some patients. Early studies indicate that the bone inhibition is a COX-1 function, suggesting that COX-2 inhibitors may not prevent heterotopic bone. Diphosphonates are not effective in prevention of heterotopic ossification and should not be used. Indomethacin may not be optimal for prophylaxis in uncemented total hip arthroplasty because ingrowth may be retarded. Irradiation may cause problems if ingrowth components are not appropriately shielded.
Table 6–8. Heterotopic Bone Classification Systems. |Favorite Table|Download (.pdf)
Table 6–8. Heterotopic Bone Classification Systems.
Islands of bone
<50% bridging laterally
Bone spurs ≥1 cm gap
>50% bridging laterally
Bone spurs <1 cm
Brooker grade 1 or 2 heterotopic ossification does not influence the outcome of total hip arthroplasty, whereas restricted ROM and pain may occur in patients with more severe grade 3 or 4 heterotopic ossification. If heterotopic ossification causes symptoms (pain, decreased ROM), surgical excision may be considered after the ossification is fully mature. Irradiation and NSAIDs are recommended postoperatively to prevent recurrence. Patients with ankylosing spondylitis have an increased chance of heterotopic ossification with arthroplasty, and in one series, the incidence of heterotopic ossification following total knee arthroplasty in patients with ankylosing spondylitis was 20%.
Prevention of infection after total hip arthroplasty is important because of the grave consequences. In the first few weeks after surgery, irrigation and debridement with retention of the prosthesis is possible. Afterward, the only way to treat an infected total hip arthroplasty is to remove the components and control the infection with antibiotics. Reinsertion of the components is then required 1.5–6 months later.
An innovation in the treatment of infected total hips and knees is the prosthetic antibiotic-loaded acrylic cement (PROSTALAC) technique. The prostheses are removed, sterilized, and reinserted as press-fit components with a layer of antibiotic-impregnated bone cement covering all surfaces except the bearing surface. This procedure is performed at the initial meticulous debridement to provide a spacer for subsequent, definitive joint replacement.
Prevention is much more desirable than subsequent treatment of infection. Total joint arthroplasty implants are such large foreign bodies that all reasonable prophylactic measures should be employed. Laminar flow and ultraviolet lights are used in operating rooms to reduce the number of viable particles per volume of air in the room. Because bacteria are shed from people, keeping the number of people in an operating room to a minimum and reducing the exposed skin area may be beneficial. Antimicrobial therapy may be the single most important prophylaxis against infection. Good surgical technique and minimal operating times also contribute to lowering of infection rates. Infections occurring 6 weeks to 3 months after surgery probably originate from intraoperative contamination. Careful surveillance in this period for signs of infection, including pain, elevated white blood cell count, fever, and wound drainage, allows for early identification of deep wound infection, and early debridement is then indicated to eradicate the infection. Similarly, large hematomas should be debrided because they may cause chronic drainage and constitute a culture media for infectious agents. One report indicates that prophylactic antibiotics given in the period before and immediately after significant dental procedures may be beneficial in preventing hematogenous infection of total joints. Probably any broad-spectrum antibiotic would provide adequate prophylaxis; the dental profession has specific recommendations. There is a growing body of information that indicates that patients who are obese undergoing total hip arthroplasty are at increased risk of infection and other complications in the perioperative period. Obesity is defined as a BMI (mass in kilograms divided by the height in meters squared) over 30 kg/m2, whereas overweight is 25–30 kg/m2. Diabetes, which is frequently present in obese patients, is also a risk factor for infection.
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Revision Total Hip Arthroplasty
The clinical success of revision total hip arthroplasty procedures historically was greatly inferior to the results of primary hip arthroplasty procedures. Loosening rates from 13% to 44% of cemented femoral revision procedures were reported at follow-up times of less than 5 years.
Improved techniques of cementing femoral stems led to improved results with cemented femoral revision. Pressurization of cement delivered, in a doughy stage, with a cement gun; pulsatile lavage; and an intramedullary plug permitted reproducible creation of adequate cement mantles. Only 14% of revised cemented femoral components were loose radiographically in one series after an average of 6 years. Other series indicate a revision rate of approximately 10% at 10 years, which is much improved from earlier series but inferior to those obtained with primary cemented stems.
Cementless reconstructions of failed femoral components were developed in response to the early high rates of failure with cemented revision procedures. However, early cementless revision series were generally unsuccessful, with failure rates of 4–10% at follow-ups of less than 4 years. The use of proximally porous coated stems with inadequate stabilization, in the setting of deficient femoral bone stock, led to unreliable bone ingrowth fixation. Encouraging reports were obtained with modular proximally coated stems, such as the S-ROM (Johnson and Johnson, Raynham, MA) prosthesis, and extensively porous coated stems, such as the AML and Solution (Depuy, Warsaw, IN). Re-revision rates from 1.5% to 6% were achieved with use of these types of cementless femoral components at follow-ups from 5 to 8.4 years.
In the situation where inadequate femoral bone stock exists, the use of allograft bone is advocated. For extended loss of proximal femoral bone stock, cementing a smooth tapered femoral stem in a bed of impacted particulate allogeneic bone produces promising short-term clinical results. When deficiency of proximal bone stock is severe, use of structural femoral allografts may be required, and short-term reports suggest good clinical results.
Similar to early experience with cemented revisions of the femoral component, acetabular revision with cement was generally unsuccessful. Because of the difficulty of interdigitating cement into a sclerotic and often deficient acetabular bone stock, failure rates of loosening were reported from 53–93% at follow-ups from only 2–4.5 years.
The introduction of cementless porous-coated acetabular implants for revision of failed cemented cups greatly facilitated early clinical results. Large hemispherical cementless acetabular implants can accommodate most bone defects encountered after removal of failed cemented cups. Where an adequate press-fit cannot be obtained, adjuvant fixation of the implant with screws or spikes can provide adequate stability to permit bone ingrowth fixation. Re-revision rates are reported from 0% to 1.6% with follow-up of 2–4 years.
Where inadequate bone stock of the acetabulum precludes reconstructions with conventional hemispherical implants, structural allografts fixed to the pelvis with screws can provide acceptable middle-term results. Other alternatives include the use of eccentric-shaped cementless implants and cemented reconstructions with particulate allografting and antiprotrusio cages.
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As with other joints, the primary indication for total knee arthroplasty is pain. Absolute contraindications to total knee arthroplasty include active sepsis, absence of an extensor mechanism, and a neuropathic joint. Relative contraindications include a patient's young (<40 years) age, heavy demand for activity, or a patient being unreliable.
When both hips and knees are involved with painful arthritis, the joint causing the most discomfort should be replaced first. If hips and knees are equally painful, hip arthroplasty should precede knee arthroplasty. Rehabilitation following total hip arthroplasty is easier and less affected by a painful knee than vice versa. Additionally, motion of the hip joint greatly facilitates surgery for the knee.
Early designs of total knee arthroplasty were developed in Europe and may be categorized as constrained or resurfacing. Constrained devices consisted of fixed hinges, and resurfacing devices relied on ligaments for stability. Constrained devices predictably loosened, although they were used primarily in severe bone or ligamentous deficiency states. Early resurfacing implants were flat, roller pin–shaped implants or unicondylar devices that replaced only the medial or lateral compartment. Early knee replacements did not resurface the patellofemoral joints.
Contemporary total knee replacements represent a convergence of two major designs developed in the United States during the early 1970s: the total condylar and the duopatellar prostheses. The total condylar prosthesis had a femoral component made of Co/Cr and an all-polyethylene tibial component with a central peg. Excision of the posterior cruciate ligament was required because the entire surface of the tibial plateau was resurfaced. The patellar component was a dome-shaped polyethylene implant. All components were fixed with acrylic cement.
The duocondylar knee replacement was the forerunner of the duopatellar prosthesis and did not resurface the patellofemoral joint. Extension of the anterior flange of the Co/Cr femoral component provided an articulation surface for an all-polyethylene dome-shaped patellar component. The tibial component was originally designed with separate medial and lateral runners, allowing preservation of the central insertion of the posterior cruciate ligament. Later, the two components were joined together, but a cutout was made posteriorly to permit retention of the posterior cruciate ligament.
Retention of the posterior cruciate ligament permitted increased flexion over that with the total condylar design because the normal femoral rollback during knee flexion was retained. Shifting of the center of rotation posteriorly during knee flexion greatly improves the lever arm of the quadriceps mechanism. The ability to climb stairs was superior when the cruciate ligament was retained. Central to the design of a cruciate ligament–retaining prosthesis is avoidance of excessive constraint by the tibial surface to permit rollback.
To overcome limitations in flexion and stair-climbing function, the total condylar prosthesis was modified with a cam mechanism (posterior-stabilized condylar prosthesis). The central cam design permits substitution of the function of the posterior cruciate ligament, providing a mechanical recreation of femoral rollback.
The differences in ROM and stair-climbing function achieved with cruciate-retaining and posterior-stabilized knee replacements are now considered negligible. Arguments in favor of the posterior-stabilized implant include technical ease in reconstructing severely deformed knees and less shear force at the articular bearing because sliding is reduced. The arguments in favor of cruciate-retaining designs are reduction of bone–cement interface forces because of less constraint, improved stability in flexion, less removal of bone from the intercondylar region, and absence of patellofemoral impingement syndrome (formed by scar tissue in the intercondylar recess of the posterior stabilized femoral component).
Problems with high-contact, stress-inducing fatigue wear of the polyethylene surfaces stimulated a new design concept in knee replacement. This design uses a polyethylene component that can move in relation to the tibial base plate. Thus, the surface of polyethylene in contact with the femoral component can be made to be more conforming because it can change positions during flexion and extension of the knee. Two types have evolved: the rotating platform, which only allows rotation of the polyethylene around an axis approximating the axis of the tibia, and variations on the “meniscal bearing” knee. In this design, the individual medial and lateral poly components can rotate (tibial axis) and translate (AP direction), or the entire poly plateau can rotate and translate in the AP direction. The latter concept seems to better address the biomechanical aspects of the knee, but results are early or limited on all designs.
Total knee replacement surgery is greatly facilitated by use of a thigh tourniquet. Following exsanguination of the lower limb with an elastic wrap, the tourniquet is inflated to an adequate pressure, usually ~300 mm Hg. An anterior midline skin incision is made, followed most commonly by a deep medial parapatellar approach. The lateral flap containing the patella is everted to allow exposure of the tibiofemoral joint. Remnants of menisci and anterior cruciate ligament are excised, with careful release of contracted soft-tissue structures as needed.
Instrumentation systems guide the surgeon to create bone cuts with a saw that match the prosthetic fixation surface and reproduce anatomic alignment of the knee joint. Typically, in the coronal plane, the tibial plateau is cut horizontally to be at a right angle with the shaft of the tibia. The distal femur is usually cut at 5–7 degrees of valgus from the shaft of the femur. Such bone cuts provide a neutral mechanical alignment in the coronal plane so a line can be drawn from the center of the femoral head, through the middle of the knee joint, and through the center of the ankle joint. In the sagittal plane, the femoral cut is at right angles to the femoral shaft, but the tibial cut is made with 3–5 degrees of posterior slope. Slight external rotation of the femoral component allows symmetric tension of collateral ligaments during knee flexion and facilitates tracking of the patellar component.
Retention or sacrifice of the posterior cruciate ligament depends on the design of the implant used. When the cruciate ligament is sacrificed, usually bone from the intercondylar notch is removed to accommodate a box that houses the cam mechanism. Other alternative designs can prevent posterior translation of the tibia on the femur. When the patellar surface is replaced, a saw is used to create a flat surface with symmetric bone thickness. Inadequate resection predisposes to subluxation because excessive extensor mechanism length is used, and the lateral ligamentous structures are relatively tightened. Many patellar components are 10 mm thick; thus, adequate resection must be almost 10 mm, within the limits of the anatomy of the patella. At least 10 mm and preferably 15 mm of patella (AP thickness) should remain. Patellar tracking is assessed by using trial components and ranging the knee from full extension to full flexion. In knees with valgus deformity, it is common to have lateral subluxation of the patella. In such cases, a careful lateral retinacular release that preserves the superior lateral geniculate vessels is performed. Positioning femoral and tibial components in slight external rotation and positioning the patellar implant slightly medially on the patellar bone surface also improves tracking.
After appropriate trials are used to confirm accurate sizes of the components as well as ligamentous stability, cementing is performed. Careful cleansing of the bone surfaces with pulsatile lavage facilitates interdigitation of doughy-stage methylmethacrylate cement. The prosthetic components must be seated in the correct orientation, and excess acrylic cement must be removed. Before closure of the knee, it is prudent to lavage fragments of bone and cement and release the tourniquet to obtain hemostasis. At surgery, little bleeding is seen in the flexed knee. Thus, many surgeons close the wound and maintain the knee in flexion for periods up to 24 hours to decrease blood loss.
Long-term results of contemporary cemented total knee arthroplasty designs are excellent. Survivorship of the total condylar prosthesis is calculated to be 90–95% at 15 years. Excellent functional results of posterior stabilized total knee replacements are also reported, with a 12-year survival rate of 94% for functional prostheses. Similarly, excellent function and only a 1% rate of loosening of the tibial or femoral component were reported with a cruciate ligament–retaining knee replacement when followed up at 10–14 years. Cementless designs have not consistently achieved the results of the cemented arthroplasties. Primary patella resurfacing is generally preferred as the best treatment path, although many surgeons prefer to leave the native patella unresurfaced.
Complications are infrequent with total knee arthroplasty but include many of the same problems encountered with total hip arthroplasty. Additional problems arise from wound healing, fracture, extensor mechanism problems, and stiffness of the knee.
DVT is common following knee arthroplasty, occurring in more than 50% of patients in one study. Further, 10–15% of patients develop DVT in the contralateral leg after unilateral knee arthroplasty. The use of the tourniquet during surgery does not have a clear detrimental effect on thrombus formation. The incidence of pulmonary embolism is lower than that reported in hip arthroplasty. This may be caused by the greater propensity to form calf thrombi after total knee arthroplasty; these thrombi may be less likely to cause emboli than thigh thrombi. Antithrombotic prophylactic measures include use of pulsatile compression stockings and administration of warfarin or low-molecular-weight heparin.
Wound problems can arise from incision-related issues and from patient-related risk factors. The skin incision should optimally be midline and longitudinal, and the skin should have minimal undermining. Preexisting skin incisions should be used when possible. Because wound healing is crucial to the success of the procedure, preoperative plastic surgery consultation may be beneficial if multiple scars, burns, or previous irradiation to the skin are present. Patient-related risk factors include chronic corticosteroid use, obesity, malnutrition, tobacco use, diabetes, and hypovolemia.
Treatment of wound problems depends on the type of problem. Drainage of serous fluid that does not clear in 5–7 days is an indication for open debridement. Hematoma formation (without drainage) is treated nonoperatively unless there are signs of impending skin necrosis or compromise of ROM. Small areas of superficial necrosis at the wound edge are treated with routine local wound care. Full-thickness soft-tissue necrosis places the joint space at high risk of infection and must be treated aggressively. Debridement with flap closure is frequently required. The medial gastrocnemius flap is useful because the tissue necrosis is frequently medial.
Prevention of wound problems through careful planning, gentle handling of soft tissues, and patient education to minimize risk factors is preferable to subsequent treatment of the problems.
Nerve palsies are a rare complication of total knee arthroplasty. The peroneal nerve is believed to be at increased risk for injury from surgery performed on valgus knees with flexion contractures or other significant deformity, ischemia from stretching small vessels in the surrounding soft tissue, and compression resulting from a tight dressing or splint. The risk is reported to be approximately 0.6%.
Notching of the anterior femoral cortex may predispose to distal femoral fracture. A technical error, notching can be prevented by careful femoral sizing before use of the anterior distal femur cutting block and by avoidance of posterior displacement or extension of the cutting block. Use of an intramedullary stem extension is advised if notching occurs. Fracture of the medial or lateral condyle may occur, particularly in patients with poor bone stock, such as those with rheumatoid osteoarthritis or osteoporosis or in patients with cruciate-sacrificing femoral components. Large intercondylar boxes in these prostheses can cause weakening of the distal femur. Similarly, tibial plateau fractures can occur because of osteopenia or even through stress concentration sites caused by pins used to fix tibial cutting blocks. These are treated by internal fixation, if needed, in combination with extended intramedullary stems to bypass the fracture site.
Patellar and Other Extensor Mechanism Complications
Many patellar and extensor mechanism problems can be prevented by careful surgical technique because many of these arise from technical problems during surgery, such as quadriceps (or patellar) tendon rupture or avulsion, patellofemoral instability, and patella fracture. Vigilance during exposure of a stiff knee to avoid excessive tension on the extensor mechanism is important. Useful techniques to avoid avulsion include a V turndown quadricepsplasty, quadriceps “snip,” tibial tubercle osteotomy, and placement of a Steinmann pin in the tubercle to prevent excessive traction on the patellar tendon. Treatment of the disruption is similar to the treatment in a normal knee. The patellar tendon is attached to bone, and the repair is protected with a wire around the patella and through the tibial tubercle, holding the patella at the correct length from the tibial tubercle. This repair complicates the postoperative ROM regimen, at least to some extent. The incidence ranges from 0.2% to 2.5%. Patellar complications include maltracking, loosening of the patellar component, fractures, and impingement. The patellofemoral forces are among the highest anywhere in the body, and avoidance of intraoperative technical errors may minimize patellar complications. Patellar tracking should be assessed intraoperatively during flexion and extension of the prosthetic knee. Lateral patellar subluxation or dislocation may be caused by internal rotation of the femoral or tibial component, as well as a tight lateral patellar retinaculum. Careful release of the lateral patellar retinaculum may correct maltracking. Subluxation can predispose to patellar component loosening, as can abnormal stress caused by uneven patellar bone resection. Excessive bone resection and avascularity, caused by damage to the superior lateral geniculate artery during lateral release, can predispose to fractures. When using a posterior stabilized prosthesis, maintaining the inferior pole of the patella within 10–30 mm of the joint line may prevent impingement syndrome, which is characterized by pain or clicking when peripatellar synovial scar tissue impinges against the intercondylar box of the femoral component during flexion and extension.
In some studies, patellar complications are the cause for as many as half of the knee revisions performed. For this reason, some surgeons do not resurface the patella when the appearance is relatively normal. Because most patellofemoral replacement problems are attributed to technical errors, inferior prosthetic design, and excessive loads, replacement will probably become more prevalent as these problems are resolved.
Knee stiffness is a common problem in the early postoperative period. Methods to reduce stiffness include physical therapy (active or active-assisted ROM) and continuous passive motion (CPM). The CPM machine moves the knee through a preset passive ROM. This modality is generally accepted and even liked by patients but does not affect the final ROM or reduce hospital stay. An acceptable ROM is 90–95 degrees of flexion with less than 10 degrees of flexion contracture, but the activities of daily living, such as getting out of a chair or climbing stairs, should be painless. Postoperative stiffness should generally subside by 6–8 weeks after surgery, and improvement in ROM should occur for 1 year with most gain in the first 3 months. The preoperative ROM is an important indicator of the ROM to be expected postoperatively.
Prevention of significant flexion contracture at the time of surgery and in the early postoperative period is important because improvement with manipulation is unrewarding. Manipulation with or without steroid injection can be beneficial in the first 3 months. Arthroscopic debridement may be necessary after intraarticular fibrosis occurs. Decreases in ROM after initial gains should alert the surgeon to possible infection, reflex sympathetic dystrophy, or mechanical problems, such as loose components or interposed soft tissue.
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Total Shoulder Arthroplasty
The primary indication for shoulder arthroplasty is persistent pain resulting from the loss of articular cartilage and incongruent joint surfaces (ie, arthritis) that has failed nonsurgical management. The most common etiologies are osteoarthritis, rheumatoid osteoarthritis, posttraumatic arthritis, cuff arthropathy, and dislocation arthropathy. Both total shoulder arthroplasty and hemiarthroplasty diminish pain. Hemiarthroplasty can be done with either a traditional stemmed humeral prosthesis or a humeral resurfacing prosthesis with similar outcomes. The humeral resurfacing prosthesis preserves bone stock, but a traditional stemmed humeral prosthesis is still best when there is humeral head bone loss that prevents the resurfacing prosthesis from being well secured. Another reason that a hemiarthroplasty is done rather than a total shoulder arthroplasty is when there is significant erosion of the glenoid beyond the base of the coracoid. This can occur in osteoarthritis but is more commonly seen in rheumatoid osteoarthritis.
Decision making in shoulder arthroplasty depends on many factors, including the integrity of the rotator cuff, capsulolabrum, and articular surfaces. Traditional total shoulder arthroplasty is not indicated in those with arthritis and who also have a torn rotator cuff that cannot be repaired at surgery. Most commonly, this is encountered in a patient who has tolerated a rotator cuff tear for many years and developed arthritis as a result. This occurs as the humerus comes to be positioned superior on the glenoid and the normal compression of the humeral head into the concavity of the glenoid, termed concavity compression, is lost. In this situation, a glenoid prosthesis would be subject to eccentric loading and a “rocking-horse effect,” which is thought to be the reason for its unacceptably high rates of loosening. Shoulder instability is not usually corrected by traditional total shoulder arthroplasty alone. In other words, performing a total shoulder arthroplasty in a shoulder that dislocates will often result in dislocation of the shoulder arthroplasty. This is because the total shoulder arthroplasty can correct damage to the articular surfaces but does not correct damage to the capsulolabrum.
The combination of a severe rotator cuff tear, joint osteoarthritis, and superior position of the humeral head on the glenoid is called cuff arthropathy and is usually associated with poor shoulder function. Surprisingly, there are some individuals with cuff arthropathy who have full ROM and little weakness. In these patients, a shoulder hemiarthroplasty is effective in diminishing pain. But when the shoulder function is poor such that the individual is unable to lift the arm against gravity, sometimes called “pseudoparalysis,” a reverse shoulder prosthesis may be best. With this design, the socket is placed on the humerus and the ball is placed on the glenoid. This prosthesis not only diminishes pain but also is a substitute for the torn rotator cuff, and function is improved postoperatively.
Contraindications to shoulder arthroplasty include infection, neuropathic arthropathy, and the absence of a functional deltoid.
A deltopectoral surgical approach is performed, with careful retraction of the conjoined tendon medially to avoid injury to the musculocutaneous nerve. Current techniques require incision of the subscapularis, and this can be done in three different manners: incision of its tendon 1 cm lateral to the insertion, detaching the tendon off the lesser tuberosity, or detaching the tendon with osteotomy of the lesser tuberosity. Osteotomy may provide opportunity for the best repair at the end of the procedure. Because there is often loss of external rotation motion in patients with shoulder arthroplasty, the subscapularis can be lengthened by attaching the tendon more medially on the lesser tuberosity or even at the edge of the humeral osteotomy. Likewise, a coronal Z-plasty of the tendon can be done to increase external rotation afterward. Many surgeons choose to incise the biceps tendon at the supraglenoid tubercle (ie, biceps tenotomy) to improve exposure. It can be tenodesed at the end if the surgeon chooses. The axillary nerve is palpated along the inferior border of the subscapularis to avoid injury. The anterior capsule is incised along with the subscapularis tendon, and some surgeons choose to resect it to improve ROM in external rotation, and then the humeral head is dislocated anteriorly with extension and external rotation of the arm and is delivered out of the wound. The humeral head is resected at the head–neck junction, while the remainder of the rotator cuff insertions remain intact. Preparation of the humeral intramedullary canal is followed by insertion of a trial stemmed humeral component in about 30 degrees of retroversion. The appropriate thickness of the humeral head is determined, and head components are trialed. Attention then moves to the glenoid. The humeral stem may be left in place to tamponade bleeding and to diminish the chances of the humerus being damaged during glenoid preparation. The humerus is displaced posteriorly using a humeral head retractor, such as a Fukuda retractor, for exposure of the glenoid. Motorized reamers or a burr are used to remove a small amount of bone so that bleeding cortical bone remains for support of the glenoid component. With osteoarthritis, there is often posterior glenoid wear necessitating removal of more anterior than posterior bone to restore normal glenoid version and provide an optimal surface for implanting the glenoid component. Using large, bulk bone grafts or cement in this situation to fill an uncontained posterior glenoid defect is not recommended. Depending on the prosthesis to be used, holes are then drilled or a keel is burred for implantation of a cemented, all-polyethene glenoid component. Keeping the glenoid bone as dry as possible during cementing is a challenge. The humeral component can be implanted with or without cement, and the subscapularis tendon is repaired. A biceps tenodesis may be done at this time as well.
Basically, there are four types of shoulder arthroplasty: humeral resurfacing prostheses with either a very small stem or no stem at all, stemmed hemiarthroplasty, total shoulder arthroplasty, and reverse total shoulder arthroplasty.
Hemiarthroplasty can be done with a humeral resurfacing prosthesis that has survivorship similar to stemmed hemiarthroplasty. Humeral resurfacing prostheses necessitate sufficient humeral head bone stock for reaming and implantation. When there is severe humeral head deformity from large osteochondral lesions or sequelae of severe humeral head fractures, for example, resection of the humeral head and implantation with a stemmed hemiarthroplasty are best. Also, in the hands of most surgeons, the humeral resurfacing prostheses do not allow adequate exposure for a glenoid component to be implanted, and a stemmed humeral component may be best.
Current total shoulder arthroplasties have nonconstrained surfaces and stemmed humeral components. These prosthetic designs incorporate modular components and sufficient sizes to accommodate differences in anatomy found in the general population. Humeral stem surfaces are available with either cemented or cementless designs. The glenoid components are all-polyethene and are pegged or keeled for cemented implantation. Metal-backed glenoid prostheses have failed at high rates. In reverse total shoulder arthroplasty, the socket is placed on the humerus, the ball is placed on the glenoid, and the surfaces are more constrained than in traditional total shoulder arthroplasty. The glenoid components have cementless designs and the humeral stem comes in both cemented and uncemented designs.
Outcomes in pain relief after shoulder arthroplasty are similar to those after hip and knee arthroplasty. Total shoulder arthroplasty alleviates about 90% of pain. There is not as much pain relief with hemiarthroplasty; pain is diminished by about two thirds. Although easier for the surgeon to perform, surprisingly, revision is more common after hemiarthroplasty done for glenohumeral osteoarthritis than total shoulder arthroplasty. Primarily for this reason, hemiarthroplasty may not be as cost-effective as total shoulder arthroplasty. Outcomes after shoulder arthroplasty are similar for those with osteoarthritis and rheumatoid arthritis.
Results after shoulder arthroplasty are not as good in younger patients as the elderly. There are many possible reasons for this, but most likely, higher activity demands and posttraumatic etiologies in younger patients result in less satisfactory results.
Improvements in function after shoulder arthroplasty are not as good as relief of pain. The best predictors of ROM and strength after shoulder arthroplasty are the ROM and strength present before surgery. Mild to moderate gains can be expected, but the patient with poor ROM and strength is likely to have persistent deficits postoperatively. Better improvements in ROM and strength can be expected in the patient with cuff arthropathy and pseudoparalysis who undergoes reverse total shoulder arthroplasty. Then restoration of about two thirds of normal ROM and strength in elevation is common.
Complications after shoulder arthroplasty are equal or less than after hip or knee arthroplasty. Today, the most common “complication” of shoulder arthroplasty is a rotator cuff tear. This occurs because rotator cuff tears are common in patients in this age group; having had a shoulder arthroplasty does not diminish the chances of a rotator cuff tear occurring. Another complication is aseptic loosening and occurs more commonly at the glenoid than the humeral prosthesis. Radiolucent lines occur around the all-polyethene glenoid component and depend on the type of prosthesis. It is more common in keeled than pegged designs. Radiolucent lines at the glenoid component are much more common than the rate of revision. Less common complications include fracture, nerve injury, instability, venous thrombosis, deep vein thrombosis, pulmonary emboli, and infection. Infection may be less than that after hip and knee arthroplasty (<0.5%) and may be due to the excellent blood supply and musculature surrounding the joint. Complications are greater in reverse total shoulder arthroplasty compared to traditional shoulder arthroplasty and are as high as 25% for primary procedures and 40% for revision procedures.
Contraindications to total shoulder arthroplasty include active shoulder infection, poor bone stock that precludes fixation of the prosthesis, the absence of a deltoid function, and neuropathic arthropathy as occurs, for example, with a cervical syrinx.
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Like other arthroplasties, the main indication for total elbow arthroplasty is persistent pain resulting from the loss of articular cartilage and incongruent joint surfaces (ie, arthritis) that has failed nonsurgical management. Etiologies include rheumatoid arthritis, osteoarthritis, and posttraumatic arthritis. However, total elbow arthroplasty is also done for distal humeral nonunions and severe comminuted distal humeral fractures, especially in the elderly. For young active patients, especially those with limited elbow motion, debridement using either an arthroscopic or open technique or interpositional arthroplasty may be best. However, it should be remembered that these are salvage procedures because they neither eliminate pain nor restore full function and are not indicated in those with preoperative instability. These procedures are for patients who are not ready to accept the limitations of a total elbow arthroplasty. Results after total elbow arthroplasty are best in elderly patients and those with rheumatoid arthritis, in part because these individuals are happy to once again use their elbows for activities of daily living.
Attention to the soft tissue, including the triceps insertion, collateral ligaments, and the ulnar nerve, is essential during total elbow arthroplasty. The direct posterior approach can be used when a semiconstrained prosthesis is used but requires dissection of the posterior skin from the underlying tissue and detachment of the triceps tendon. Careful soft-tissue handling and repair of the triceps tendon afterward are essential to avoid skin necrosis and weakness of the triceps muscle. The Bryan posteromedial approach is also used for implantation of semiconstrained devices. The surgical plane is between the medial triceps and forearm flexors proximally and between the flexor carpi ulnaris and flexor carpi radialis distally. This allows direct visualization of the ulnar nerve and facilitates transposition of the nerve. Great care should be taken when elevating the triceps from its insertion on the olecranon so that it remains in continuity with the forearm fascia. With this approach, total elbow arthroplasty can be done without detachment of the triceps. Release of the collateral ligaments is required. Because integrity of the collateral ligaments is vital when a nonconstrained device is used, the Kocher posterolateral approach may be best because it allows preservation of the ulnar collateral ligament. This ligament provides the major restraint against valgus forces in the flexed elbow. The surgical plane is between the anconeus and extensor carpi ulnaris muscles distally and proximally between the triceps and brachioradialis muscles.
Today's total elbow arthroplasty designs have less constraint, permitting more normal elbow kinematics than in the past. Both unconstrained and semiconstrained prostheses diminish pain, and complications are similar. The two currently available types of total elbow arthroplasty include semiconstrained and resurfacing nonconstrained prostheses. Semiconstrained prostheses have stems on both the humerus and the ulna and a linked hinge that provides stability. Excision of the radial head is usual during implantation. They are not a simple hinge and, instead, have been called a “sloppy hinge” by some, hence their name semiconstrained. This lessened constraint has resulted in much better survivorship; highly constrained total elbow arthroplasty prostheses failed due to loosening. Dislocation is not a concern with semiconstrained prostheses. Semiconstrained prostheses are best when there is instability or loss of bone stock. In theory, nonconstrained implants load the prosthesis less and yield less aseptic loosening. Because stability is not conferred from the prosthesis, they should not be used in cases of ligamentous instability or loss of bone stock.
Radial head prostheses have long been available for severe fractures of the radial head. They may also be an aid in providing stability in the elbow with a comminuted radial head fracture. Short-term results are excellent and remain good over 10 years, although arthritis of the capitellum, radiolucencies along the stem, and other problems occur; long-term follow-up is needed. Hemiarthroplasty is now available for severe fractures of the distal humerus. Early outcomes are encouraging.
Total elbow arthroplasty has survivorship that may be as high as 85% at 10 years, but patient selection, compliance, and age are critical factors to success. In patients who have had a total elbow arthroplasty for posttraumatic arthritis, failure is much more common. Failure is also more common in younger patients, under 65 years of age. Outcome is similar in elderly patients who have had total elbow arthroplasty for treatment of osteoarthritis and rheumatoid osteoarthritis. Total elbow arthroplasty reliably improves functional ROM and strength in most patients. Even in those with ankylosis after posttraumatic arthritis, improvements of about 80 degrees of ROM occur in the flexion and extension arc.
Complications are more common than with other total joint arthroplasties, and the short-term complication rate (within the first year) may be as high as 10%. Complications include aseptic loosening, joint instability, fracture, ulnar neuropathy, wound complications, venous thrombosis, pulmonary emboli, and infection. Ulnar neuropathies do not usually require an additional procedure, paresthesias are usually transient, and motor weakness is rare. Many patients with rheumatoid osteoarthritis have ulnar neuropathy before surgery, and the total elbow arthroplasty may not have contributed significantly to postoperative symptoms. Aseptic loosening, metallosis, severe polyethylene bushing wear in semiconstrained devices, instability in nonconstrained devices, and infection are reasons for revision. For aseptic loosening, revision with a longer stemmed prosthesis usually suffices. Impaction bone grafting into the endosteal canal of the distal humerus or proximal ulna is also an option. Polyethylene bushing wear is diagnosed from diminished space between the humeral and ulnar components on radiographs.
Contraindications to total elbow arthroplasty include active shoulder infection, poor bone stock that precludes fixation of the prosthesis, neuropathic arthropathy as occurs for example with a cervical syrinx, and the absence of biceps and triceps function.
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The total ankle arthroplasty was under development for many years as a result of the success with total joint replacement of the knee and the hip. Initial designs met with modest short-term success and caused almost an abandonment of the procedure because of the comparison to ankle arthrodesis. The longevity of total ankle joint replacements has been somewhat erratic for a variety of reasons. The articular surface that must be replaced is unlike any other joint, and thus experience cannot be carried directly from the knee or the hip to the ankle. Joint loads and requirements are less well characterized, and surgical technique is less well developed and, therefore, less reliable. For these reasons, total ankle replacement had been a developmental procedure indicated for patients with low activity demand and the need for ankle motion. In 2006, the FDA approved two new and improved designs that have renewed interest in this procedure.
Total ankle replacement is desirable because of the drawbacks of ankle arthrodesis, which include a significant pseudoarthrosis rate of 10–20%, despite extended cast immobilization to achieve arthrodesis. Furthermore, arthrodesis results in osteopenia and diminished motion in the subtalar and midtarsal joints. The additional stress on these joints from the ankle arthrodesis predisposes them to degenerative changes over the long term, as is seen frequently above and below the arthrodesis in other joints such as the cervical spine, the lumbar spine, and the hip.
Chou LB, Coughlin MT, Hansen S Jr, et al: Osteoarthritis of the ankle: the role of arthroplasty. J Am Acad Orthop Surg
Guyer AJ, Richardson G: Current concepts review: total ankle arthroplasty. Foot Ankle Int
Raikin SM, Kane J, Ciminiello ME: Risk factors for incision–healing complications following total ankle arthroplasty. J Bone Joint Surg Am
Evaluation of Painful Total Joint Arthroplasty
A certain degree of adaptation and accommodation is possible in the normal joint, allowing it to last for a lifetime in most persons. After replacement of a diseased joint by a metal-and-plastic artificial joint, no remodeling or accommodation is possible. Loosening of the interface between bone and prosthesis is possible and, indeed, may be inevitable. In addition, during and subsequent to the implantation process, bacteria may find their way into a prosthetic joint, causing pain or loosening. Implantation of a new joint markedly alters the stress state in the bone, particularly with uncemented prostheses, and a certain amount of pain may result. The presence of the new joint is likely to alleviate pain markedly, and the patient's activity level may increase, resulting in bone remodeling around the prosthesis or at a remote site or even fatigue fractures. All of these problems may result in a painful arthroplasty. Evaluation is complicated by the presence of the artificial joint, which introduces several new variables when compared with a normal arthritic joint. The same process of evaluation is used as with an arthritic joint; a history is obtained, physical examination is performed, and laboratory data are obtained.
Referred pain from other sources must be ruled out, particularly with the shoulder and the hip, where referred pain from the lumbar and cervical spine may confuse the picture. A history of pain radiating into the shoulder with motion of the neck, for example, may be helpful in this process. Pain related to activity of the affected joint, as compared with pain all the time, is an important fact, with constant pain or night pain suggesting chronic infection. Pain in the hip or knee that occurs with the first few steps but then improves somewhat with further ambulation is likely to be caused by loosening of the prosthesis. This pain probably arises from a fibrous membrane between the prosthesis and bone, which, with weight bearing, compresses and provides better contact, thereby lessening the pain. A history of swelling, redness, fevers, or chills must be obtained, which is suggestive of an infectious etiology for the painful joint. Also suggestive of infection is excessive drainage or delayed wound healing or skin necrosis in the postoperative period of the initial implantation.
The same tests are performed as for an arthritic joint to evaluate the location, magnitude, and severity of pain.
Laboratory data may be helpful. The ESR (>35–40 mm/h) or C-reactive protein (CRP) (>0.7) points toward an infected arthroplasty; with the knee, a lower ESR does not rule out infected arthroplasty. A complete blood count is also sometimes helpful in demonstrating an elevated white blood cell count.
These data are less helpful in the early postoperative period. The CRP will be elevated after surgery and should trend to normal by 6 weeks after surgery. The ESR rises after surgery, peaks at about 2 weeks after surgery, and returns to normal by 6 months after surgery. The skin temperature is elevated due to inflammation after surgery and averages 4.5°C higher than the normal knee at 2 weeks and slowly decreases to within 1°C at 6 months after surgery.
Arthrographic evaluation may be helpful by showing dye penetration into the cement–bone interface, prosthesis–bone interface, or prosthesis–cement interface. The most important aspect of arthrographic evaluation is the fluid obtained for culture and for cell count and differential. A high percentage of polymorphonuclear leukocytes (>90%) is highly suggestive of infection, despite a low cell count or negative culture. Arthrographic evaluation is mainly indicated when infection is suspected because there is a risk of contaminating the joint as well as the possibility of obtaining false-positive and false-negative cultures. Another important aspect of arthrographic evaluation is the pain response to injection of lidocaine into the joint. Alleviation of essentially all pain when weight bearing is attempted after injection localizes the problem to the affected joint.
Indium-Labeled White Blood Cell Scan
Bone scans have little value immediately after surgery. Significant bone remodeling is present, which continues for several months. Bone scans may not be helpful until 6 months to 1 year after surgery. At that point, increased uptake indicates bone remodeling and loosening or infection of the prosthesis. The indium-labeled white blood cell scan can be useful immediately after surgery or in the face possible acute infection.
This nuclear medicine study uses the patient's polymorphonuclear leukocytes, which are labeled with radioactive indium and injected back into the patient. It may be quite beneficial in localizing acute infectious processes but is frequently not helpful in the evaluation of chronic infection.
Radiographic examination is the single most useful test in the evaluation of nonseptic loosening. Important signs are radiolucent lines adjacent to the prosthesis or cement, particularly if they are 2 mm or greater or are becoming enlarged on serial radiographs (Figure 6–11). Fracture of the cement and change in position of the component are indications of loosening.
Radiograph of radiolucent lines around an acetabular component.
Honsawek S, Deepaisarnsakul B, Tanavalee A, et al: Relationship of serum IL-6, C-reactive protein, ESR and knee skin temperature after total knee arthroplasty: a prospective study. Int Orthop
Lee SC, Jung KA, Yoon JY, et al: Analysis of synovial fluid in culture-negative samples of suspicious periprosthetic infections. Orthopedics
Treatment of Infected Total Joint Arthroplasty
Definitive evidence of a septic total joint arthroplasty forecasts a poor prognosis for the patient. The infectious process is either acute or chronic, and the infection is either gram negative or gram positive. Either the components are tightly fixed to bone or one or more of the components is loose. In acute infection with tightly fixed components, most surgeons debride the joint without removing the components and treat the infection locally and with systemic antibiotic therapy. A chronically infected or loose prosthesis is usually treated with removal of the prosthesis, local wound care, and systemic antimicrobial therapy. Therapy for an acutely infected, firmly fixed prosthesis varies according to surgeon preference.
There is general concurrence that thorough debridement of the joint, synovectomy, removal of necrotic material, and copious irrigation are necessary at the time of debridement. Because of the potential presence of glycocalyx, surfaces of the prosthesis available for inspection are scrubbed with Dakin solution, which dissolves the glycocalyx. Removable components are removed, and the undersurfaces are cleaned with Dakin solution. New polyethylene components are inserted if available; if this is not possible, the old polyethylene prosthesis is scrubbed with Dakin solution and reinserted. To prevent superinfection, the wound must be tightly closed. To help eradicate the existing infection, however, irrigation and drainage must be continued. One suitable method is that described by Jergesen and Jawetz, in which small volumes of antibiotic solution are instilled into the joint twice a day, and the joint is sealed off for 3 hours, followed by 9 hours of suction (Figure 6–12). This protocol begins 24 hours after surgery, during which time suction drainage is maintained. The instillation-suction system is maintained for 10 days. At the end of the course of irrigation and instillation, a culture is aspirated from the joint after one antibiotic instillation. This system can also be used for osteomyelitis and routine joint infections. Antibiotics are continued for an appropriate period of time (usually 6 weeks) after the tubes are withdrawn.
Schematic diagram of the Jergesen system of instillation of antibiotics. The antibiotics can be varied depending on the susceptibility of the infecting bacteria (fungus). The amount instilled is approximately 5 mL per tube plus the dead space from the valve to the joint.
In cases of loose prostheses, little alternative is available except to remove the prosthesis. A similar system of instillation and suction is then used, using the same protocol. If reimplantation is likely after infected total knee prosthesis, an antibiotic cement block is used to separate the bone ends and maintain a potential joint space. An alternative to the cement block is the PROSTALAC system as described earlier. This technique has the benefit of maintaining hip or knee joint muscle length and elasticity. In patients in whom reimplantation is planned, the ESR is followed monthly until it is normal without antibiotic therapy. In patients with rheumatoid osteoarthritis or other disorders in which the rate may be elevated, 6 months is an appropriate time to wait for possible recrudescence of the infection. At this point, either an aspiration arthrogram or a Craig needle biopsy is used to obtain specimens for culture. If these are negative, reimplantation surgery is planned.