Median nerve displacement through the carpal canal.

We determined the direct relationships between wrist position and displacement of the median nerve during active contraction of the flexor tendons at the wrist with an intact, transected transverse carpal ligament (TCL). Nine fresh cadavers were mounted in an apparatus to allow variable wrist position. Excursions of the tendons and displacement of the median nerve were measured by tracking markers with a video camera. Each limb was tested at 0 degree, 30 degrees, and 60 degrees of wrist extension before and after release of the TCL. Excursion of the flexor tendons required for full finger flexion ranged from 2.3 to 3.1 cm (mean, 3 cm). Median nerve displacement ranged from 0.9 to 1.4 cm (mean, 1 cm). The relationship between median nerve and flexor tendon excursion was consistently linear. Finger motion alone allows for median nerve displacement after surgery in the carpal tunnel.