Plate 234

Repair of the lacerated flexor tendon should only be performed under ideal conditions, because the best (and sometimes only) opportunity for a good functional result is the first attempt at repair. Presence of severe contamination, infection or massive tissue destruction should be a contraindication for immediate repair. Debridement and wound preparation should be performed first with delayed repair performed at a later time.

There are five zones of injury established in the literature (Figure 1). Each zone has its own method of repair. Traditionally, zone II injuries (within the flexor tendon sheath) were known as “no man's land” because of the poor results of repairs in this zone. Today, with proper surgical repair and aggressive and comprehensive rehabilitation by a specialized hand therapy service, even these patients can have satisfactory return of function.

General or axillary block anesthesia may be used. Regional blocks of the wrist or elbow of the median, ulnar, and radial nerves can also be performed. These blocks can be of benefit in the emergency room while the patient is awaiting surgery. Digital blocks are generally of little use in this setting.

Prior to surgery, the wound should be cleansed thoroughly (as tolerated) in the emergency room and a sterile dressing applied. Once adequate anesthesia is obtained, exsanguination of the arm is performed with gravity or an elastic bandage and a tourniquet should be placed on the upper arm. In the normal adult, a blood pressure cuff is inflated to 250 mmHg, or at least 80 mmHg above systolic blood pressure. This tourniquet may be left inflated for 2 hours. It may be reinflated again after a 20-minute period of normal circulation. The wound is then uncovered and thoroughly irrigated with several liters of warm saline.

Exposure must be adequate. It is usually necessary to extend the original limits of the wound (Figure 2). However, care must be taken that the extending incisions are anatomic that they parallel flexion creases in the palm, and that they do not cut across flexion creases in the wrist. Incisions in the digits should be based on the laceration pattern. For lacerations that are oblique on the digit, Brunner-style diagonal incisions between interphalangeal joints should be utilized. For transverse lacerations, axial incisions should be performed. It is imperative to keep the digital skin flaps widely based to prevent ischemia. The neurovascular bundles of the digits lie along the lateral volar surface of the digit and should be protected at all costs. Poorly made incisions may result in skin compromise and deformity.

Debridement and exploration of the involved area are carried out. Adjacent nerves and vessels are identified and retracted. If possible, the tendon ends are located in the wound and gently grasped with forceps (Figure 3). Gentle tissue handling is of utmost importance, as crush injury to the tendon can lead to poor healing, gapping of the repair, and eventual failure. Lacerations that involve less than 60% of the cross-section of the tendon do not need to be repaired. The loose fibers should only be trimmed to prevent catching of the tendon on the flexor pulleys. Complete transections and those greater than 60% require repair. Depending on the location of the laceration, the proximal tendon stump may retract and require maneuvers to retrieve it. Retrieval should be atraumatic and under direct visualization if possible. Flexing the wrist and elbow and squeezing the muscles of the forearm can help deliver the proximal stump to the incision. Sometimes counter incisions proximal in the palm or forearm need to be performed to identify the tendon. Generally, the distal segment is identified easily with finger flexion. In multiple tendon injury cases, care must be taken to confirm the anatomy and orientation of the proximal and distal tendons. General principles of tendon suturing have evolved over time, with both multi-strand core sutures and epitendinous sutures proving their benefit. A running, epitendinous suture line of 6-0 permanent monofilament suture provides both strength and a smooth gliding surface. Frequently the “back wall” epitendinous repair will be performed first, followed by a multi-strand core suture repair with 3-0 or 4-0 permanent suture, finished by epitendinous repair of the “front wall” to complete the repair. For both epitendinous and core suturing, there are several methods described (Figures 4 and 5). The most reliable core sutures are performed with locking four-strand repair techniques and most epitendinous repairs are performed in a running fashion (simple, locking, horizontal mattress).

Zone I injuries (distal to the insertion of the flexor digitorum superficialis tendon on the middle phalanx) usually require percutaneous button suturing of the proximal tendon to the distal phalanx due to the frequent shortage of distal tendon available (Figure 6). Zone II injuries (within the flexor sheath) are the most difficult cases and should only be attempted by a surgeon experienced with these injuries. Both the flexor digitorum superficialis and profundus tendons (FDS and FDP, respectively) should be repaired. Zone III injuries (in the palm) are generally more straightforward and heal well. Zone IV injuries (within the carpal tunnel under the transverse carpal ligament) are rare and are frequently associated with injuries to the median nerve. Zone V injuries (in the forearm) can be complicated if the injury occurs at the musculotendinous junction, as muscle does not hold sutures securely. Potential injury to the arteries and nerves of the forearm need to be evaluated.

Once all repairs have been completed, the tourniquet is released and meticulous hemostasis is achieved. The field must be dry before closure is attempted.

Deep soft tissues are approximated to eliminate dead space; subcutaneous tissue and skin are closed in the usual manner with fine sutures.

Nonadherent gauze is placed over the wound and a dorsal block splint is fashioned to prevent extension of the wrist and fingers. It is important to make sure the splint extends beyond the ends of the fingers. The splint is fashioned to keep the fingers and wrist in slight flexion to keep tension off the flexor tendon repair (Figure 7). Postoperatively, the hand is kept elevated to reduce edema.

The initial dressing and splint is kept in place for a couple days. The patient then is enrolled in a comprehensive hand therapy program monitored by the surgeon and a certified hand therapist. Most programs start with passive exercises in the first week. Depending on the patient's compliance and motivation and the quality of the tendon repair, some patients may start an early active motion protocol. Early motion of tendon repairs has been shown to reduce the amount of scarring and subsequent stiffness in repaired tendons, but is balanced by the increased risk of tendon repair rupture if therapy is more aggressive than the repair can support. Patient compliance with the postoperative therapy is the largest determinant of outcome for tendon laceration repairs.