Cadaver study of the topography of the musculotendinous junction of the finger extensor muscles: applicability to tendon rupture following closed wrist trauma

Rupture of the extensor pollicis longus (EPL) tendon in the wrist is a delayed complication that can occur after wrist injury. Several etiology-related hypotheses have been made to explain these ruptures. The one most commonly accepted is necrosis at the musculotendinous junction of the EPL, which is compressed between the extensor retinaculum and dorsal aspect of the radius. To confirm this hypothesis, we performed an anatomical study to show the close relationship between the extensor retinaculum and the musculotendinous junction of the EPL muscle. We calculated the distance between the musculotendinous junction of the various finger extensor muscles and the proximal edge of the extensor retinaculum. We were able to show that this junction is located under the extensor retinaculum for the extensor indicis (EI) and EPL muscles, but the latter is in the third extensor compartment, which is a tight, confined space. Any pressure increase in this space following trauma, for example, can bring about compartment syndrome at this musculotendinous junction, which some authors have found to be poorly vascularized.