Second metatarsophalangeal joint: biomechanics and reconstruction potential.

A damaged distal radioulnar joint results in instability, pain, and loss of motion. This amounts to function loss. Of the many proposed reconstructive procedures, only a vascularized joint transfer offers growth potential in children and durability. The well-studied vascular anatomy and minimal donor morbidity of the second metatarsophalangeal joint makes it a potentially useful source. The authors evaluated various biomechanical aspects of the second metatarsophalangeal joint, which included the mediolateral arc of movement of the second metatarsophalangeal joint in hyperextension when subjected to lateral stress loading; the different patterns of disruption at peak load; and the flexion and extension range of movement. Twenty-six cadaveric specimens were tested with a customized jig. The results showed that the mediolateral arc of movement of 114 degrees approximates that of the flexion and extension range of movement of 114.2 degrees. However, it differed in that it was equal in both directions, compared with an extension arc that was greater than a flexion arc. The peak load was approximately 100 N, and this resulted in fracture, avulsion, and ligament tear. These biomechanical results may be useful to reconstructive surgeons.