Repair of flexor tendon injuries has come a long way since the days when surgical repair in “no man’s land” repair was contraindicated. As surgeons have become skilled and knowledgeable about intrasynovial repair, suture techniques have become more sophisticated, and rehabilitation protocols have kept pace with surgical advances. The indication for primary repair in an adult is a medically fit patient who can demonstrate compliance with a postoperative rehabilitation and splinting protocol. Emergent repair of lacerated tendons is primarily indicated only in the setting of compromised perfusion, which requires microvascular repair. Optimal timing of a flexor tendon injury in an otherwise perfused digit is within 7 to 10 days from injury.

In examining a patient with a flexor tendon injury, the flexion cascade of the hand will be altered (Figure 1). This can be more subtle when only one of the two flexors in the finger is injured or when a partial laceration exists. To test for flexor digitorum superficialis (FDS) function, hold the uninvolved digits with the metacarpal phalangeal (MP) joints in hyperextension and the interphalangeal (IP) joints in extension and ask the patient to flex the proximal interphalangeal joint (PIPJ) of the involved finger. To test for flexor digitorum profundus (FDP) function, hold the involved digit at the middle phalanx level and ask the patient to flex the distal interphalangeal joint (DIPJ) of the involved digit. Use of the wrist extension-flexion tenodesis effect can indirectly enhance the examination, especially in the patient who is reluctant to be examined directly (tone of flexors increases with passive wrist extension when the tendon is intact). If the flexor pollicis longus (FPL) is lacerated, compression of the muscle belly proximal to the wrist may assist in demonstrating interphalangeal (IP) flexion of the thumb. The presence of a “pseudotendon,” which occurs with retraction of the tendon subsequent to a laceration, may mimic an intact tendon, leading to conservative treatment when repair is in fact necessary.

The level of the volar skin laceration may not represent the true level of the tendon injury, especially if the laceration occurred while the digits were flexed. In this case, the tendon laceration may be distal to the level of the skin laceration. Palpation of the palm may reveal the level of the retracted stump in the form of a lump. Although uncommon, the surgeon should check the digit for absent flexion creases, which is a sine qua non for congenital flexor tendon deficiency; this entity can be mistaken for an acute tendon injury.

Finally, the presence or absence of the palmaris tendon (both on the injured and uninjured side) should be noted. The patient should be prepared for the possibility of the unexpected need for graft or subsequent two-stage reconstructive procedure. Alternative options for tendon graft such as plantaris tendon or extensor digitorum longus toe extensors may be needed in the absence of a palmaris longus, and the possible need for this contingency should be discussed preoperatively with the patient.

Plain radiographs of the affected digit and hand are obtained at the time of initial evaluation and are beneficial in evaluating an avulsion injury or the presence of foreign body (Figure 2). Depending on mechanism of injury, plain imaging can also help rule out associated carpal fractures, dislocations, and metacarpal fractures. Additional advanced imaging, such as ultrasonography and MRI, can be useful when the continuity of the tendon is in question and in assessing the gap distance between the ruptured tendon ends² (Figure 3).