Direct Repair Approaches

Minimizing the time between injury and surgery is desirable. With the passage of time the likelihood of a tendon–muscle contracture is greater, complicating the surgical tactics. The passage of time also increases the likelihood that soft tissue changes at the fibro-osseous tunnel will interfere with successful gliding of a repaired or reconstructed flexor tendon. Nevertheless, in some instances a delay in repair is inevitable due to the timing of the referral, associated injuries, and other considerations. During the first several weeks after an acute flexor tendon injury, a direct repair is usually possible. However, the goal is restoration of the preinjury length–tension relationship of the injured flexor tendon. Therefore, it behooves the surgeon to attempt to restore normal length–tension relationships prior to or during the repair surgery.

The simplest technique for restoring relationships in the contracted muscle–tendon unit is to retrieve the proximal end of the tendon and apply tension. Retrieval of the proximal tendon is discussed in Chapter 35 on acute flexor tendon injuries. Retrieval can be performed (1) by carefully grasping the tendon within the fibro-osseous tunnel system proximally toward the wrist using a fine mosquito or tendon passer, (2) by making proximal “windows” in the fibro-osseous tunnel system until the proximal tendon end can be grasped and then sequentially delivered distally along the fibro-osseous tunnel system using surgical instruments, or (3) by passing suture into the proximal stump and delivering the tendon utilizing the suture from proximal to distal windows and eventually to the site of the distal stump. Sometimes a stainless steel wire loop or red rubber catheter can facilitate passage of the tendon and tendon suture.

Using an instrument such as Kelly’s or Kocher’s clamp, 5 minutes of manual tension by the surgeon can, in some circumstances, successfully restore the muscle–tendon unit to preinjury status and overcome early myostatic changes. If this is achieved, and the quality of the fibro-osseous tunnel is acceptable (in instances where the critical A2 and A4 pulleys are functioning and intact), the protocol for acute flexor tendon laceration with direct repair using multistrand techniques can be performed.

Myriad repair techniques are available. They should all take advantage of a multistrand core system, and the use of a peripheral suture to both improve gliding potential and add additional strength to the tendon repair. If the tendon does not revert to its original length–tension relationship, the surgeon can consider several options.

Flexor Digitorum Profundus Avulsion Injuries

FDP tendon avulsion injuries fall into several injury categories. In Leddy type II injuries with modest retraction of the avulsed tendon to the level of Camper’s chiasm, or in Leddy type III injuries with avulsions that stay at the DIP joint level, primary repair can generally be performed even if delayed past 6 weeks because retraction and length–tension changes are modest. In Leddy type I injuries, the avulsed FDP tendon retracts into the palm, and vincular injury, sheath hematoma, and myostatic contracture ensues. Generally after 6 weeks, primary repair is not possible, and the following described surgical techniques can be employed. The decision in this situation is whether to perform delayed flexor tendon reconstruction for the FDP tendon, as outlined in the introduction, in the face of normal FDS function in order to improve overall digital function. ^,

Direct Repair with Lengthening at the Musculotendinous Junction

For direct repair with lengthening at the musculotendinous junction the surgeon makes a proximal incision in the forearm and identifies the affected flexor tendon. To identify the proper muscle–tendon units, one uses standard techniques with a sequential application of tension applied proximally in the forearm to the individual units, noting the end effect in the various digits. The lacerated unit has an abnormally blunted or complete lack of digital flexion effect, depending on the extent and location of laceration. Once the appropriate tendon has been identified, the musculotendinous juncture is carefully dissected with scissor technique while manual tension is applied on the distal portion of the muscle–tendon unit using a Kessler or Bunnell suture on the tendon to pull on the unit and provide some tension. By dissecting the fibers of the muscle as they insert on the tendon itself, approximately a centimeter of length can be achieved without full disruption of the muscle to the proximal tendon. If there are some concerns about the integrity of this juncture, sutures can be applied to reinforce the muscle relationship to the tendon using mattress-type sutures or a Bunnell weave. This technique works when approximately a centimeter of length or less will restore normal length–tension relationships. After this is achieved, a delayed primary repair of the flexor tendon can be performed.

Direct Repair with Z -Lengthening of the Tendon in the Palm

An alternative to the previously described technique is to perform the delayed primary repair of the muscle–tendon unit first by suturing the distal flexor tendon injury. In this case, the resting position of the digit exhibits abnormally increased flexion compared with its neighbors, and the normal “cascade” of the digits in a resting position is disrupted. At this point, after repair at this juncture, if the injury is in zone 1 or zone 2 of the fibro-osseous tunnel, a proximal lengthening can be performed by a Z -lengthening of the tendon in the palm level. A longitudinal split of approximately 3 cm is performed using a tongue depressor and a #15 or #11 blade. This allows increased length in the muscle–tendon unit proximal to the direct repair, which can be adjusted so that normal length–tension relationships are restored. Once the appropriate lengthening has been achieved, three nonabsorbable mattress sutures are placed to create a secure robust side-to-side repair between the two lengthened split limbs of the tendon. If planned appropriately, this juncture lies proximal to the fibro-osseous tunnel and distal to the carpal canal ( Fig. 37-1 ).

A, This 28-year-old woman sustained a work injury when she fell off of a ladder. She sustained a laceration to her fourth finger with loss of digital flexion at the distal interphalangeal (DIP) joint and loss of sensibility in the finger. The patient was taken to surgery 1 month after the injury due to authorization issues with her workman’s compensation case. B, Intraoperatively, the proximal and distal tendon ends were identified and mobilized in zone 2 and repaired with a 3-0 Ticron suture ×2. Because of the chronic contracture despite stretching of the proximal muscle–tendon unit, the patient had loss of normal cascade. A decision was made to perform a Z -lengthening of the flexor digitoum profundus tendon proximal to the level of the repair to avoid the use of an interposition tendon graft or a Z -stage tendon reconstruction with silicone rod. C, The postoperative extension block orthosis is seen as well as the pulley ring to protect the A4 pulley. D, Postoperatively, the patient gradually regained normal motion of the proximal interphalangeal joint, and with gripping, excellent DIP joint motion and strength were restored as indicated on the dynamometer.

Immediate Tendon Grafting

If the quality of the fibro-osseous tunnel is reasonable but the gap distance between the proximal and distal ends is quite long and cannot be overcome by the above-mentioned techniques, then immediate tendon grafting can be considered. Short-segment immediate tendon grafting can be performed by a repair to the proximal and distal junctures of the cut ends of the tendon. The type of suture used is dictated by the location of the injury. If the injuries are at the level of the fibro-osseous tunnel, then the standard zone 1 or zone 2 flexor tendon repair techniques are required. Alternatively, the distal FDP tendon can be debrided and the tendon graft attached to the FDP stump and to the bone. There are several ways to do this. In short-segment flexor tendon grafting, the proximal stump may lie proximal to zone 2, in the midpalm in zone 3, in which case a more bulky but stronger repair may be acceptable.

Depending on the placement of the proximal juncture or the amount of damage to the proximal muscle–tendon unit, the surgeon may elect to perform a long tendon graft and have the proximal tendon end come proximal to the wrist and be sutured into the muscle–tendon donor near the musculotendinous junction. This places the proximal repair far away from the zone of injury and where the bulk of the repair will not be affected either underneath the transverse carpal ligament or by the fibro-osseous tunnel constraints. Also, the repair can be performed as a tendon weave, and in this way a robust repair can be performed that is unlikely to rupture.

Superficialis Finger

The surgeon and patient may elect to have a “superficialis” finger in any of the following circumstances: when there is significant damage to the FDP tendon, when the DIP joint is damaged, when the quality of the fibro-osseous tunnel from the PIP joint distally is severely compromised, when complex bone and joint injuries occur distal to the PIP joint, or when there is damage to the A4 pulley system. In this technique the function of digital flexion is provided by FDS only. When an isolated zone 1 injury occurs, which is the only flexor tendon injury, and a superficialis muscle–tendon unit is intact, tendon reconstruction is not required. In this case addressing the associated soft tissue problems is appropriate. Additionally, depending on the laxity of the DIP joint and the possibility of hyperextension or “joint collapse” with pinch, either tenodesis using a distal stump of FDP or arthrodesis using pin or screws across the DIP joint after preparation of DIP joint for arthrodesis can be performed. If the proximal FDP stump is tender to palpation or deep pressure when gripping functions are performed, excision of the proximal stump to shorten it so the proximal end lies in the proximal palm, carpal canal, or forearm is indicated. This may be an acceptable reconstruction, given the lengthy alternative of staged tendon reconstruction or when the expectation of success of staged tendon reconstruction is guarded given concomitant injury to the digit.

Pulley Reconstruction

Staged tendon reconstruction may be desirable in the face of simultaneous tendon and pulley damage since it is difficult to successfully reconstruct a critical pulley and a flexor tendon and to rehabilitate both simultaneously. In these cases a staged tendon reconstruction is an excellent choice, with formal pulley reconstruction being performed at the time of the index (stage one) operation. The benefit of this staged tendon reconstruction is that with passive tendon rods there is no significant tension on the pulley, which is given an opportunity to heal prior to passage of an active tendon unit, tendon rod, or tendon graft.

The traditional pulley reconstructions utilize flexor tendon remnants, either FDP for staged flexor tendon reconstruction in which flexor tendon is sacrificed or in situations where FDS can be removed for the purposes of tendon pulley reconstruction.

An alternative source can be extensor or flexor retinaculum from the wrist. This alternative has the advantage of thinner tissue, which still has good strength. The desired repair at the proximal phalanx level for the A2 pulley is to have a continuous loop of tissue that is passed dorsally underneath the extensor apparatus and between the extensor and the dorsum of the proximal phalanx bone and volarly at the level of the fibro-osseous tunnel. It can be sutured to itself and supplemental sutures placed to the surrounding soft tissue. Alternatively, remnants of the fibro-osseous tunnel attachment to the phalanx itself can be utilized to suture the graft, or used as a belt loop to pass the graft through. In this way, a non-360-degree circumferential pulley reconstruction can be performed. This can be a much weaker pulley reconstruction, however, and has a higher likelihood of failure than 360-degree circumferential pulley grafts.

At the level of the middle phalanx for the A4 pulley, the pulley reconstruction can have a 360-degree circumferential loop—in this case superficial to the extensor tendon mechanism dorsally as it goes into the terminal tendon insertion of the DIP joint level ( Fig. 37-2 ).

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