Flexor Tendon Repair for a Zone 2 FDP Tendon Laceration

This case is of a zone 2 flexor tendon repair for flexor tendon injury in a little finger. The attending surgeon presents a repair with a 4-0 Ethibond suture with a modified Kessler stitch which resulted in an 8-core strand repair. The procedure was done under wide awake local anesthesia no tourniquet (WALANT) protocol, which among other strengths allows the surgeon to test the repair and set postrehabilitation expectations for the patient. The procedure starts with a Brunner incision and is closed with 5-0 chromic suture in a horizontal mattress fashion. After closure, a dorsal extension block plaster splint was applied. The indication for this surgery was to restore little finger flexion at the distal interphalangeal (DIP) joint. Finger flexor tendons include the flexor digitorum superficialis (FDS) and flexor digitorum profundis (FDP). Common causes of zone 2 flexor tendon injuries include superficial and deep lacerations to the volar aspect of the hand, crush injuries, and saw blade cuts. Early surgical repair is the definitive treatment for greater than 60% rupture of tendon. Postoperatively, patients undergo active extension – passive flexion to achieve functional gliding of the tendon. Patients can expect to return to light activities after 6–8 weeks and resume heavy activities around 10–12 weeks.

Flexor tendon injuries include trauma to the flexor digitorum superficialis (FDS), flexor digitorum profundis (FDP), or flexor pollicis longus (FPL) tendons. Injuries to these tendons are considered rare, with an incidence of 4.83 per 100,000 persons in 2018.1 Flexor tendon injuries are primarily described by injury location first outlined by Kleinert and Verdan in five specific zones.^1, 2

 Zone 1: Region from FDS insertion to the FDP tendon.

 Zone 2: The proximal aspect of the A1 pulley to the FDS insertion.

 Zone 3: Distal transverse aspect of the carpal ligament to the A1 pulley.

 Zone 4: The carpal tunnel. 

 Zone 5: Proximal border of the transverse carpal ligament to the musculotendinous junction in the proximal forearm.

Flexor tendon injuries frequently lead to the inability to flex the fingers in the hand, necessitating a surgical repair, preferably within ten days of injury.³ 

Patients often present with a loss of active flexion of the distal interphalangeal (DIP) or proximal interphalangeal (PIP) joint in the involved digit with complete tears. Knowing the mechanism or injury (clean or dirty knife) can help make decisions that impact peri and postoperative care.⁴

Patient’s right little finger rests in extension. This patient presents with an altered cascade and an inability to flex DIP with intact PIP flexion. Passive ROM intact. A 2-cm laceration present at volar base of the metacarpophalangeal (MCP) joint that was closed with suture. Neurovascularly intact in all fingers and the hand and wrist.

Radiographs may be obtained to rule out an associated fracture. An ultrasound may be used to assess suspected lacerations.

Without prompt surgical intervention to repair a flexor tendon rupture, healing by primary tendon repair may no longer be possible due to proximal tendon end swelling, tendon contraction, and muscle fibrosis. If no intervention is performed, the patient can experience a decrease in finger flexion strength and ROM due to the development of scar tissue and retraction of the tendon proximally.⁵ This is especially true with zone 2 injuries where the presence of multiple pulleys and intervening tendons impair the free motion of the tendon.⁶ 

Treatment options vary significantly when addressing partial versus complete tendon ruptures. A survey completed in 1995 found that 75% of surveyed hand surgeons would repair partial tendon lacerations greater than 50% of the tendon.⁷ More recent studies show that cutoff has risen to 60%.⁴ However, the standard of care for complete tendon rupture—as in this case—is surgical repair. The timeline for repair is debated; however, there is a consensus that the sooner the repair, the better the outcome. Postoperative rehabilitation includes active extension – passive flexion to achieve function and gliding, while avoiding rupture of the tendons.⁸

There exists a multitude of techniques for surgeons to repair the tendon; however, tendon repair is a companion of core and peripheral sutures, both contributing to the strength of the repair. Studies have shown that strength of tendon repair is proportional to the number of sutures that cross the repair site.^9, 10 The choice of suture material for tendon repair is highly variable and dependent on the surgeon’s preference and individual experience.¹¹ Recent studies are also shedding light on the concept that in the setting of a strong core suture, a lack of peripheral sutures produced no postsurgical rupture of the tendon repair.¹² 

Surgical tendon repair was done in this case to establish flexor function across the DIP joint. Repair was accomplished with a 4-0 Ethibond suture with a modified Kessler stitch which resulted in a 2-core strand repair. Ideally a 4- or 6-stand repair is used; therefore, additional sutures are placed to augment the repair site resulting in an 8-core strand repair with an epitendinous stitch placed as well. 

Primary repair of the tendon is contraindicated in cases of severe multiple tissue injuries to the fingers, when the wounds are dirty or contaminated, or when there has been skin loss overlying the flexor system.¹³

This case presents a zone 2 tendon injury repair involving the reattachment of the FDP tendon after a complete rupture. Outcomes for tendon injury repair vary significantly based on the mechanism of injury. Outcomes are worse with concomitant fractures, nerve injuries, contaminated wounds, crush injuries, and injuries that occur with tearing mechanisms such as a saw or lathe.^13-16 Patients can expect to return to light activities after 6–8 weeks and resume heavy activities around 10–12 weeks. Successful rehabilitation includes active extension – passive flexion exercises to promote strong and successful healing. Early rehabilitation can start at 3 days post-op if adequate repair was able to be performed.

Typical surgical time for this procedure is around 30–60 minutes, and it can be performed under sedation or wide awake with local anesthetic (WALANT). Benefits of the WALANT technique include increased safety and convenience, decreased cost, the ability to test strength and complications of repair, and to show the patient the expected functional goals with proper postoperative rehabilitation. Complications of tendon repair include adhesion formation, joint contractures, tendon rerupture, triggering, bowstringing, quadriga, and other common complications after surgical interventions.¹⁷ Risk of complications are lowered with proper surgical technique and rehabilitation course.  

The best technique for use in zone 2 tendon repairs remains unclear to date. There exists significant variation among the type of sutures, the number of strands, use of core and peripheral strands, and the type of suture stitching technique. Due to force restraints of the need for early active motion of the finger, it is generally believed that a four-strand core suture (with a 4-0 or 3-0 non-absorbable suture) is a minimum requirement.¹⁸ Many surgeons use six, eight, or more stranded sutures for increased strength of repair. Care should be taken to avoid bulky and twisted sutures, which can interfere with smooth gliding of the tendon. Tang (2013) outlined that partial venting of the A2 pulley can be effective in allowing greater degree of tendon motion if the other annular pulleys are intact and release is less than 2 cm.¹⁸ One notable change in outcomes is the decrease in rate of rupture for zone 2 flexor tendon repairs. A review of the rates of rupture ranges from 0–5% over the past decade and a half.¹⁸ Further research is currently being conducted as to the optimal use of all these factors based on clinical in vivo human studies. 

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Nothing to disclose.

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.

The authors would like to thank the operating room staff for their help in making this video.