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. The presence of severe contamination, infection, or massive tissue destruction should be a contraindication for immediate repair. Debridement and wound preparation should be performed emergently, but definitive repair may be performed safely at a later time (ideally less than a week from injury). Extensor tendon repair is relatively more straightforward. Extensor tendons bear less force, and delayed repair is more forgiving. Flexor tendon repair is more demanding, particularly where the tendon excursion occurs within the confines of a tunnel of tendon sheath and a series of pulleys. In addition, because of proximity, flexor tendon injuries of the hands are typically associated with arterial and nerve lacerations. Ideally, artery and nerve repair should precede tendon repair. In cases where access to microscopic capabilities is limited and there is no clinically apparent vascular embarrassment of the digit distal to the injury, then there is no mandate for repair of arterial injury. Sensory nerve repair can be delayed if recognition is delayed (with recognition that repair of the nerve is most easily accomplished prior to attempted flexor tendon repair).
There are five zones of injury for flexor tendons (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 early history of poor results of attempted 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. The surgical goals of repair are similar to those of other repairs elsewhere: precise coaptation of viable tissues without unnecessary shortening. Additionally, there is a requirement to minimize the resistance of the repair itself—which will need to glide through the tendon sheath while maintaining the strength of the repair.
General or axillary block anesthesia may be used. Regional blocks of the wrist or elbow of the median, ulnar, and radial nerves also can 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. The hand may be splinted in a safe position to minimize potential displacement of the proximal cut end of the tendon (particularly the flexor tendons, which can withdraw proximally and offer a greater challenge to deliver into the operative field). Once adequate anesthesia is obtained, a time-out is performed. Exsanguination of the arm is performed with gravity or an elastic bandage, and a tourniquet should be ...