I found the article on using ultrasound to diagnosis closed flexor tendon injuries interesting. I still rely on history and physical exam to make the diagnosis, but can see how the use of ultrasound (US) could be useful particularly in children.
- To test the FDP tendon, the examiner holds the other fingers in extension and stabilizes MCP and PIP joints. The patient is then asked to flex the distal phalanx.
- To test the FDS tendon, the examiner holds the other fingers in extension, but the MCP and PIP joints are released. The patient is asked to flex the finger. The PIP joint and, to a lesser degree, the MCP joint should flex. About 20% of patients are missing a FDS tendon in the little finger and will therefore 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 3 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.
- Passive manipulation of the wrist through flexion and extension should result in extension and flexion of the digits, respectively. This uses the tenodesis effect of the antagonistic tendons. If a tendon is transected, then there can be no tenodesis effect.
- 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.
Sagittal image of the ring finger reveals the gap (red arrows) between the torn ends of the FDP and also depicts the intact flexor digitorum superficialis tendon (green arrows)