Abstract
Extensor tendon attachment to the dorsum of the proximal phalanx may fully extend the finger metacarpal phalangeal joint (MPJ). 15 fresh-frozen cadaveric hands were axially loaded in the line of pull to the extensor digitorum comunis of the index, middle, ring and small finger at the level just proximal to the MPJ. We measured force of extension at the MP joint in 3 groups: 1) native specimen, 2) extensor tendon release at the proximal interphalangeal (PIP) joint with release of lumbricals/lateral bands, 3) extensor tendon release at the PIP joint and dorsal proximal phalanx and lumbrical/lateral band release. Degree change of extension was calculated using arctan function with height change of the distal aspect of the proximal phalanx, and the length of the proximal phalanx. We used Student T-test to determine significant decrease in the extension of the phalanges. Extension of all fingers decreased slightly when the extensor tendon were severed at the PIP joint with release of the lateral bands/lumbricals (8deg+/−2deg). After this release, the finger no longer extended. Slight loss of extension was not statistically significant (p >.05) between group 1 and group 2. Groups 1 and 2 were significantly different compared to group 3. In summary, distal extensor tendon transection and release of lateral bands/lumbricals resulted in little change in force and degree of finger extension. The distal insertion of the extensor, released when exposing the PIP joint dorsally, may not need to be repaired to the base of the middle phalanx.
