In Zones I, II, and III, a zigzag, or Bruner, incision can be made to expose the injured area (Figure 28.3). Alternatively, a midlateral incision can be used. In either case, the incisions can be modified slightly to incorporate the traumatic laceration. These approaches allow visualization of the neurovascular bundles and assessment of any other injury that might require concomitant repair. It may be necessary to release one or more of the flexor pulleys to expose the injury site, as long as the integrity of the A2 and A4 pulleys is maintained. After tendon repair, if passive flexion or extension of the digit causes impingement of the repair site on the A2 or A4 pulleys, these can be vented to facilitate postoperative ROM. If these pulleys
are completely disrupted by the injury or are iatrogenically released, they should be repaired prior to closure. However, the A1 and A3 pulleys should be left unrepaired to improve tendon gliding at the repair site. For Zones IV and V, a volar Henry approach to the forearm with extension to the carpal tunnel can be used.

Prior to any flexor tendon repair, identification and retrieval of the severed tendon ends must be performed with as little trauma as possible to the surrounding tissue to minimize subsequent adhesions within the tendon sheath. All injuries can result in retraction of the proximal tendon end, especially with increasing time from injury. This becomes less likely in distal injuries, in which the vincula to the tendons may prevent retraction to the palm. For Zone I injuries, the Leddy classification is used to describe the level to which the FDP tendon has retracted and whether any bony avulsion is present (Figure 28.4).

In both Zone I and II injuries, retrieval of the proximal tendon end can sometimes be accomplished by milking the forearm and palm, and a small, narrow instrument can be passed beneath the pulleys to attempt to grasp the tendon. If this is unsuccessful, it may be necessary to extend or make a separate proximal incision to identify and retrieve the tendon. Once the lacerated tendon is identified proximally, we prefer to
pass a pediatric feeding tube from distal to proximal though the pulleys (Figure 28.5). The feeding tube is then sutured to the tendon and helps guide passage back to the site of injury. The tendon ends can then be held in place for repair using a small-gauge needle. In Zones II, III, and IV injuries, the distal tendon stump will often be more distal than the skin laceration if the fingers were flexed at the time of injury; therefore, the approach must be extended distally accordingly.

An ideal repair of the injured tendon will provide the maximal strength to resist failure during postoperative rehabilitation, while still allowing adequate vascularity and contact of the tendon ends to facilitate healing. For injuries in Zones II through V, there have been numerous studies regarding the number of core sutures to cross the repair site, the size of the suture, and the type of suture technique. The author’s preferred method uses 3-0 monofilament, non-absorbable suture in a four-strand core repair. To create this we prefer the suture configuration depicted in Figure 28.6, although many suture configurations can be used, including a Kessler-style suture with a looped suture (two strands per pass). An epitendinous repair is also performed with 6-0 monofilament, nonabsorbable suture with attention paid to avoid placing the knot on the volar side of the repair (Figure 28.7). Meticulous handling and suturing of the tendon ends, using an epitendinous suture to minimize the bulk of the repair, as well as employing techniques such as pulley venting or FDS slip excision, may facilitate tendon gliding and help minimize the amount of adhesion formation.

The strength of the repair is a major predictor of rupture risk. The number of suture strands that cross the repair site is directly proportional to the repair strength. For instance, a
four-strand repair has been shown to be twice as strong as a two-strand repair. Strickland estimates from prior studies that repairs have 50% of their strength at 1 week, 67% at 3 weeks, and, finally, 120% strength at 6 weeks. The addition of an epitendinous repair has been shown to decrease gapping at the repair site and increase the strength of the repair by 10% to 50%. Therefore, the combination of a four-strand repair and an epitendinous suture should provide enough strength to withstand light active grip even at the weakest time point of 1 week. Studies have shown no definitive consensus for the recommended suture, material, or size that is most optimal for repair strength and healing.

For Zone II injuries in which the FDS and FDP are both injured, there is some debate regarding whether the FDS should be repaired. Repair of both slips of FDS may inhibit tendon gliding beneath the A2 pulley and promote adhesions. However, even though the loss of FDS does not cause a major functional deficit, it may serve as an important source of blood flow to the FDP. The authors therefore prefer to repair at least one slip of the FDS as long as it does not cause significant gliding resistance; otherwise, it is excised. The repair should then be observed as it glides beneath the pulley system. The A1, A3, and A5 pulleys can potentially be sacrificed to improve gliding. For the A2 and A4 pulleys, if the pulley impedes full passive flexion or extension of the digit, partial venting of the pulley may be appropriate to allow full motion to be achieved.

Zone I injuries are unique and the repair method varies depending on the presence or absence of a bony avulsion fracture. The most common repair methods include suture anchors, sutures tied over a dorsal button, or sutures tied directly over the bone. If the avulsed bony fragment is large enough for open reduction and internal fixation, this can be accomplished with either small screws or Kirschner wires.