Procedure 8 Acute Repair of Zone 2 Flexor Tendon Injury

See Video 5: Acute Repair of Zone 2 Flexor Tendon Injury

Figure 8-7 is adapted from Tang JB. Flexor tendon repair in zone 2C. J Hand Surg [Br]. 1994;19:72-75, with permission from Elsevier. Figure 8-18 is adapted from Strickland JW. Development of flexor tendon surgery: twenty-five years of progress. J Hand Surg [Am]. 2000;25:214-235, with permission from Elsevier.

Examination/Imaging

Clinical Examination

Patients present with loss of active distal interphalangeal (DIP) and proximal interphalangeal (PIP) joint flexion if both FDP and FDS are divided, or loss of only DIP joint flexion if only FDP has been injured. On inspection, the normal finger cascade is lost with the affected digit in an extended position.

The function of the FDP is determined by asking the patient to actively flex the DIP joint of the involved finger.

Testing for FDS injury is more complex compared with the FDP because the PIP joint is flexed both by the FDS and by the FDP. Therefore, one needs to check the function of the FDS while blocking the action of the FDP.

• The standard test for the FDS takes advantage of the fact that the FDP tendons to the long, ring, and small fingers share a common muscle belly. The finger being tested is allowed to flex while the action of the FDP tendon is blocked by preventing flexion of the DIP joint of the other two fingers (Fig. 8-1). The standard test is not reliable for the index finger because the index finger FDP has an independent muscle belly (Fig. 8-2). In addition, the action of the FDS of the small finger may be dependent on the FDS to the ring finger, and they may need to be tested together (Fig. 8-3).

• Mishra described a modified test whereby the subject is asked to press the fingertip pulp of all the fingers together against the proximal part of the palm, such that the DIP joint is kept extended. If the FDS is acting, the DIP joint remains in a position of extension to hypertension while the MCPJ and PIPJ are fully flexed. If the FDS of any of the fingers is injured or absent, the DIP joint goes into flexion. This test works on the principle that the FDP can flex the PIP joint only after it has flexed the DIP joint. If the DIP joint is maintained in extension, PIP joint flexion is purely a function of the FDS (Fig. 8-4).

A partial tendon laceration should be suspected in patients in whom active motion is associated with pain or triggering.

In patients who cannot cooperate (e.g., children or comatose or intoxicated patients), one can look for passive movement of the fingers resulting from the wrist tenodesis effect or by squeezing the forearm muscles (Fig. 8-5). The same maneuvers can be used when trying to differentiate between tendon injury and inability to move as a result of nerve palsy.

It is important to examine the patient for presence of concomitant injuries to the digital arteries and nerves.

FIGURE 8-1

FIGURE 8-2

FIGURE 8-3

FIGURE 8-4

FIGURE 8-5

Imaging

Preoperative imaging studies are not typically necessary, but anteroposterior and lateral x-rays may help identify associated bony injury. When a patient presents with unstable or intra-articular fractures, rigid fixation of the fracture is performed so that judicious tendon mobilization can be performed after tendon repair.

Surgical Anatomy

Zone 2 contains both the FDS and FDP tendons and extends from the proximal edge of the A1 pulley in the palm to the insertion of the FDS over the middle phalanx. It includes four annular pulleys (A1, A2, A3, and A4) and two cruciate pulleys (C1 and C2) (Fig. 8-6).

Zone 2 was subdivided by Tang (1994) into four subzones (Fig. 8-7).

• 2A: Includes the C2 and A4 pulleys and has the FDS insertion. Only the FDP tendon glides under the A4 pulley. The A4 pulley is located at the midpoint of the middle phalanx and is 0.5 to 0.8 cm long.

• 2B: Includes the C1 and A3 pulleys and has the chiasm portion of the FDS.

• 2C: Includes the A2 pulley and represents the narrowest segment of zone 2. The A2 pulley is about 2 cm long and is situated over the proximal two thirds of the proximal phalanx. The middle and distal parts of the A2 pulley are very narrow, and the FDS tendon bifurcates within the midpart of the A2 pulley.

• 2D: Includes the A1 pulley and represents the widest portion of zone 2.

The blood supply to the tendons in this region comes from the vincular system and enters the tendon on the dorsal surface. It is recommended that core sutures be passed in the palmar portion of the tendon.

FIGURE 8-6

FIGURE 8-7

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