History
Careful attention to the patient's history and the mechanism of injury can often alert the hand surgeon to the extent of the pathology. [8] Finger position at the time of injury is important. If the injury occurred while the finger was in flexion, the level of the tendon injury will be distal to the skin laceration. A finger that is injured in the extended position will have a tendon injury that closely corresponds to the skin laceration.
Physical Examination
The natural resting position of the hand should be closely observed to determine whether the normal composite cascade of the fingers has been disrupted.
In the uninjured hand, the composite flexion of the fingers increases from the radial to the ulnar side. The finger with a tendon disruption nests in a more extended position. If only the flexor digitorum profundus (FDP) tendon has been transected, the flexion of the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints may be within the normal cascade, but the distal interphalangeal (DIP) joint will be extended. A finger in which the flexor digitorum superficialis (FDS) tendon and the FDP tendon are disrupted will lie flat in an extended position outside the normal cascade of fingers.
A thorough, formal examination of the FDS and FDP tendons is important because testing these tendons may reveal partial lacerations. A partial laceration may present with pain when the patient attempts to flex against resistance. A thorough neurovascular examination is warranted to alert the surgeon to the possible need for microsurgical repair of the vessels or nerves. [9]
The integrity of FDS and FDP tendons should be tested independently and in tandem. The examiner holds the other fingers in extension and stabilizes the MCP and PIP joints. To test the FDP tendon, the patient flexes the distal phalanx. To test the FDS tendon, MCP and PIP joints are released, distal phalanges are kept extended, and the patient flexes the finger. The PIP joint and, to a lesser degree, the MCP joint should flex. About 20% of patients are missing an FDS tendon in the little finger and thus have limited or no PIP flexion during testing.
For flexor pollicis longus (FPL) testing, the thumb MCP joint is stabilized in neutral position. The patient is asked to flex the interphalangeal (IP) joint against resistance. A communication may exist between the FPL and the index FDP. The examiner stabilizes the other three digits. The patient opposes his or her thumb to the little-finger MCP joint. Flexion of the index distal phalanx proves the existence of this anomalous communication.
There are two additional ways by which the integrity of the flexor tendon can be evaluated. Passively manipulating the wrist through flexion and extension results in extension and flexion of the digits, respectively. This test uses the tenodesis effect of the antagonistic tendons. Compression of the forearm flexion muscles also can be used to test the integrity of the flexor tendons in the hand. As the forearm is compressed, the digits are drawn into flexion. Transected tendons in the digits do not flex with this maneuver, nor do they extend and flex with the tenodesis test.
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Flexor tendons with attached vincula.
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Retinacular portion of flexor tendon sheath.
