Zone II Flexor Tendon Repair Utilizing a Tendon Passing Aid

The surgical repair of zone II flexor lacerations is historically associated with unique intraoperative and postoperative challenges.1–4 Challenges to zone II flexor tendon repairs include considering time to surgery, navigating the overlying digital segmental annular pulleys, ensuring a strong repair that allows for early postoperative mobilization, and proactively decreasing other factors that increase resistance to tendon gliding.4,5 These injuries can also involve lacerations of adjacent neurovascular structures. Recent literature demonstrates several technical advancements to maximize patient outcomes following zone II repairs, including the M-Tang repair.4,6 As addressed in this technique, an additional technical challenge associated with zone II tendon repairs is the retrieval of injured tendons when retracted proximally. Multiple methods have been described pertaining to the retrieval and repair of a retracted tendon.4,7 Noninvasive options include proximal-distal milking or reverse Esmarch bandaging. When noninvasive retrieval fails, invasive options through the primary incision include endoscopic retrieval, suction, blind grasping with rigid or flexible forceps, or “walking” the tendon with needles, hooks, or forceps. While these options prevent the need for a significant extension of the primary incision, they can increase damage to the injured proximal tendon end and tendon sheath. If retrieval through the primary incision fails, a palmar incision proximal to the A1 pulley can be made to aid in the retrieval process. Techniques of retrieval from the proximal incision include “walking” the tendon with needles, hooks, or forceps, end-to-end suturing to a suction catheter or small tube, side-to-side suturing to a catheter or tube, retrieval with a Seldinger catheter, or using an aneurysmal needle.7 Tang4 described utilizing 2 sets of forceps to gradually walk the tendon distally within the tendon sheath. Each of these options has its own unique risks, primarily regarding the preservation of the tendon’s blood supply, orientation, and atraumatic length. This article describes the use of The QuickPass Tendon Shuttle Small (Arthrex [AR-8090S], Naples, FL) for end-to-end retrieval of a retracted flexor tendon through a proximal, palmar incision (Fig. 1). This tendon shuttle has previously been utilized in tendon transfer cases in the hand, foot, and ankle that require passing a tendon through bone tunnels. Advantages of using this device include maintaining the orientation of the tendon as it is passed through the flexor sheath, minimizing damage to the pulleys, and the “Chinese finger trap” mechanism of the shuttle that allows for a uniform grasp of the tendon without significant compression. The rigid end of the shuttle facilitates a more streamlined passage through the flexor sheath, while the flexible end applies tension to the tendon, pulling it through the sheath, facilitating a minimally traumatic reunion of the proximal FDP to the repair site.FIGURE 1: Intraoperative image of the tendon shuttle. Arrow identifies the “finger trap” portion used to secure the proximally retracted tendon to the shuttle. The red circle identifies the rigid portion of the tendon shuttle, used to guide the tendon back to the distal incision site. This end is blunted with suture scissors before insertion in the flexor tendon sheath.TECHNIQUE A video illustrating the described surgical procedure is available for viewing (Video, Supplemental Digital Content 1, https://links.lww.com/TIO/A87 demonstrating modified flexor tendon retrieval during zone II Flexor Tendon Repair). The patient was positioned supine on the operating table with the injured left upper extremity placed on an arm table. The patient received general anesthesia, a nonsterile tourniquet was applied proximal to the elbow, and the affected arm was prepped and draped in the usual sterile fashion. The tourniquet was inflated in accordance with the patient’s blood pressure. Using a Tupper’s board and retractors, the hand and uninjured digits were secured to improve visualization and facilitate repair. The traumatic laceration had previously been sutured upon initial injury. This was reopened and the hematoma was evacuated (Fig. 2A). A Bruner’s incision was progressed distal to the laceration over the middle phalanx to visualize the retracted FDS and FDP tendons. Hemostasis was achieved using bipolar diathermy. The flexor tendon sheath, flexor tendons, and digital neurovascular bundles were bluntly dissected. In this case, the tendon sheath had been breached midway through the A3 pulley. The FDS and FDP tendons were fully lacerated and the proximal ends had retracted into the tendon sheath. At this point, careful inspection of the digital artery and nerve was paramount to prevent further injury and facilitate eventual repair. This patient had injuries to the radial digital artery and nerve. Adequate collateral circulation to the distal phalanx was present; therefore, the artery was ligated with hemoclips. The distal flexor sheath was then explored and the distal ends of the FDS and FDP tendons were found proximal to the A4 pulley. The FDS was still intact at its distal attachment site. Flexing the injured finger at the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints can help facilitate the delivery of the distal tendon stumps if they have retracted. It is the senior author’s preference to repair the FDP tendon only in zone II repairs. The FDS tendon stump was debrided and excised close to its insertion site, while the FDP tendon was minimally debrided in preparation for repair.FIGURE 2: A, Exposure of the traumatic laceration through a distal Brunner’s incision. B, Placement of the 1 cm palmar incision proximal to the A1 pulley. C, Isolation of the proximally retracted FDP tendon and attachment to the tendon shuttle using 4-0 suture. D, Insertion of the rigid shuttle guide into the flexor tendon sheath after it is blunted with suture scissors.The first attempt at retrieving the proximal FDP stump utilized small pickup forceps through the tendon sheath. However, due to the extent of tendon retraction, this trial was unsuccessful. Therefore, the decision was made to retrieve the FDP and FDS tendons through an incision in the palm (Fig. 2B). The palm was palpated to locate the injured flexor tendons and attempt to determine the extent of retraction. A 1.5 cm transverse incision was made proximal to the A1 pulley over the palpated tendon. The tendon sheath was identified, and incised, facilitating retrieval of FDS and FDP. A hemostat was inserted under the proximal tendons and The FDS was excised as proximally as possible. The proximal FDP tendon was inserted 1.5 to 2 cm into the fingertrap portion of the tendon shuttle and secured using a 4-0 suture (Fig. 2C). Choice of the suture is dependent upon surgeon preference, however, 4-0 Vicryl has worked best during the previous experience. The suture was passed through the midsubstance of the tendon and wrapped circumferentially ∼1 to 1.5 cm proximal to the end to ensure the integrity of the eventual repair site. The pointed end of the tendon shuttle was made smooth by cutting it with suture scissors. The flexor tendon sheath was directly visualized in the proximal incision and the rigid end of the tendon shuttle is advanced through the sheath and delivered to the distal portion of the wound (Fig. 2D). It is important to maintain proper orientation of the tendon during the shuttling maneuver. Pickups were used at the primary repair site to aid in the delivery of the proximal tendon and the tendon shuttle was fully passed through the wound (Fig. 3A). Once delivered, the tendon shuttle was removed by releasing the securing stitch and a 25-gauge needle was used to fix the tendon within the primary incision to prevent retraction (Fig. 3B).FIGURE 3: A, Rigid tendon shuttle guide appears in the distal incision site. B, Once the retracted tendon is delivered to the primary repair site, the tendon shuttle is removed and is secured using a 25-gauge needle. C, Microscopic view of the final tendon repair through the M-Tang technique and digital nerve repair. D, Closure of all incisions with 4-0 suture.Repair of the ruptured tendon can be performed according to the operating surgeon’s preference. In this case, the FDP tendon ends were then repaired using the M-Tang technique with a 6-stranded core suture through 4-0 fiberloop and a running epitendinous stitch using 6-0 Prolene (Fig. 3C).4,6 Although the repair was unable to be assessed through active motion, several assessments were performed to evaluate the repair before closing. Repair and gliding of the tendon was confirmed using the forearm squeeze test.8 Repair was also confirmed by pulling on the FDP tendon through the proximal incision in the palm. Observation of DIP, PIP, and MCP flexion without triggering or catching confirmed successful repair. A resting finger cascade was observed and was restored to normal. In this case, the radial digital nerve was transected during the initial injury which was repaired under microscopic magnification with nerve allograft (Axogen) (Fig. 3C). The wounds were washed using normal saline and then closed using interrupted 4-0 nylon sutures (Fig. 3D). Wounds were dressed and a dorsal blocking plaster splint was applied with the wrist in 20 degrees of flexion, MCP joints at 60 degrees of flexion, and IP joints in full extension. Postoperatively, the patient began early range of motion activities per the St. John early active range of motion rehabilitation protocol.9 The patient was seen in the clinic between days 3 and 5 for dressing changes and wound check. At that time, a custom splint was applied with the wrist in neutral, MCP joints at 60 degree of flexion, and IP joints in full extension. The splint was utilized for 6 weeks, only to be taken off for exercises and therapy. Follow-up clinic appointments occur at 2 weeks, 6 weeks, 3 months, 6 months, and 1 year postoperatively. The patient is also seen twice weekly for hand therapy for the first 6 weeks, then once to twice weekly for the next 6 weeks. EXPECTED OUTCOMES The modifications included in this technique build upon that described by Tang.4,6 This approach allows for exposure of the lacerated flexor tendon through the laceration as well as a 1 to 1.5 cm palmar incision, allowing the surgeon to avoid a lengthy proximal extension of the incision. The primary advantage of utilizing the tendon shuttle is to allow for the delivery of the proximal FDP to the repair site in the correct orientation without significant damage to the tendon. This technique is advantageous, especially in cases where delayed surgical intervention or tendon retraction are concerns. In the technique described by Tang, the FDP tendon is grasped with 2 sets of forceps and pushed distally toward the digit in a grasp and push fashion until the proximal FDP is delivered. Even with the use of blunt forceps, there is a theoretical risk to cause damage to the tendon as well as the overlying synovial flexor sheath cover at the repair site. The synovial flexor sheath cover contains a flattened layer of fibroblast known as the epitenon. The epitenon is a crucial gliding surface that must be restored to improve the odds of successful tendon repair.10 In addition, reducing the incision size decreases edema and inflammation, potentially minimizing postoperative wound complications and scar contracture. This method allows for meticulous soft tissue handling, which is especially important in zone II repairs, to decrease adhesion formation.1 Although this modification adds additional steps to the repair, it has been used in ∼20 cases by the corresponding author to successfully reunite the lacerated ends of the flexor tendon during flexor tendon repairs. It is also reasonable to mention the potential logistical concern regarding the availability of the tendon shuttle and the additional associated cost of ∼$89 to 92. COMPLICATIONS The use of the tendon shuttle is meant to streamline the passage of the proximal FDP to the repair site in a manner that protects the tendon and its anatomic orientation within the sheath. If any concerns are encountered, any of the previously described methods, such as the Tang technique using blunt forceps, can still be utilized. A potential complication associated with this technique includes injury to surrounding structures, especially the flexor sheath, with forceful passage of the rigid portion of the shuttle. To mitigate this risk, the pointed end of the shuttle should be cut to a blunt edge using scissors. Also, the surgeon should visually identify the flexor tendon sheath and ensure accurate insertion of the tendon shuttle. The shuttle should glide smoothly within the flexor sheath. If resistance is met, the shuttle should be removed and repositioned. In addition, disruption of the suture attachment may occur if excessive tension is applied to pull the shuttle through the flexor sheath. In the event that the tendon shuttle device separates from the proximal tendon, this would require returning to the palmar incision to identify the proximal tendon and reattempt attachment to the tendon shuttle. Although not previously encountered or anticipated, if at any point there is concern for tendon injury or injury to adjacent structures, appropriate care should be taken to identify and repair the structures as needed. To optimize the design of the tendon shuttle to better suit this procedure, future models should include an inherent blunt tip, the use of a more malleable material for the solid end of the shuttle to allow it to more easily conform to the structure of the flexor sheath as it is being passed through, and a build in suture at the terminal portion of the finger trap end to secure the tendon.