9 Flexor Tendon Rupture
9.1 Patient History Leading to the Specific Problem
A 36-year-old man was seen in our unit with inability of active flexion of the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints of the left index finger, 3 weeks after primary flexor tendon repair of the flexor digitorum profundus (FDP) tendon in another hospital (▶Fig. 9.1).
His FDP tendon had been repaired with the two-strand modified Kessler method and a simple running peripheral suture following a cut in the middle part of the proximal phalanx. He started active motion at the beginning of week 3 after immobilization and passive finger motion in the first 2 weeks after surgery. He noted he could not actively flex the DIP or PIP joints of the repaired finger and was diagnosed as having a rupture of the repaired FDP tendon of the left index finger.
9.2 Anatomic Description of the Patient’s Current Status
The site of this patient’s initial flexor tendon laceration was in anatomic zone 2 of the digital flexor tendon; the exact location is zone 2B (▶Fig. 9.2a). In this area, the tendon has to glide into zone 2C (i.e., the A2 pulley area) to flex the finger. The surgical repair of the tendon in zone 2B is particularly prone to disruption if the repair is weak, for example, a two-strand Kessler repair (as was the case in this patient), or if the repair site has no tension (which tends to allow the repair site to gap during active finger motion, easily becoming entrapped at the edge of the A2 pulley). The A2 pulley, which is rigid and narrow, 1.5- to 1.8-cm long, is located over the proximal two-thirds of the proximal phalanx. This pulley hinders the gliding of the repaired but still edematous FDP tendon after surgery and significantly increases resistance to tendon gliding. The area of the A2 pulley is the most anatomically complex in zone 2. The narrowest parts of the A2 pulley are its distal and middle portions (▶Fig. 9.2b).
During this patient’s initial primary repair by relatively inexperienced surgeons, the A2 pulley was not vented. Subsequently, the repaired FDP tendon disrupted after commencement of active motion of the repaired finger.
Fig. 9.1 The left index finger exposed to confirm disruption of the repair after the patient was found unable to actively flex the finger 3 weeks after initial primary repair.
9.3 Recommended Solution to the Problem
Complications of rupture of the primarily repaired tendon can be prevented by using strong repair techniques, such as a multistrand core suture, and venting of a part of the A2 pulley or the entire A4 pulley depending on the location of the tendon repair. The author prefers a six-strand core suture plus a simple running peripheral suture, though others generally recommend a core suture of four strands or more. The addition of two strands to a four-strand core repair may add only 5 minutes to the procedure, but ensures a much greater safety margin for early active digital motion. The author always uses a six-strand repair with 4–0 (or sometimes 3–0) suture, using either an M-Tang core repair (▶Fig. 9.3a) or a six-strand (three groups) asymmetric Kessler repair (▶Fig. 9.3b). The author uses the six-strand repair methods for re-repair of ruptures of primarily repaired FDP tendons.
As for the decision between re-repair of the disrupted FDP tendon and secondary tendon grafting, the author re-repairs a rupture if it occurs within 4 to 5 weeks after the initial repair. Within that period, it is possible to redo a primary repair of the disrupted tendon after proper trimming of the softened or ragged tendon ends. In the author’s experience, such a re-repair is practical and a good solution. Ruptures 5 weeks after initial tendon repair are rare but should be treated secondarily with tendon grafting.
Fig. 9.2 Flexor tendons and pulleys in the fingers. (a) Zone and subdivisions of the zone 2 of the finger. (b) Anatomy of the A2 and A4 pulleys with amplified view of anatomy of the A2 pulley. The narrow parts of the A2 pulley are from a1b1 to a2b2, which are at the distal and middle portions of the A2 pulley.