Bioabsorbable pin fixation of intercarpal joints: an evaluation of fixation stiffness

Objective. Bioabsorbable pins made of poly-p-dioxanone (Johnson and Johnson Orthopaedics, Raynham, Massachusetts) were compared to steel pins in the fixation of the scapholunate and lunotriquetral intercarpal joints of the wrist. Design. An in vitro experiment was performed using fresh-frozen cadaver wrists. Background. In the surgical treatment of wrist ligament injuries, temporary intercarpal joint fixation is required. Although steel pins are currently used, there are several clinical problems associated with their use. These complications could potentially be reduced by using bioabsorbable fixation. Methods. The carpal bones were mounted between sets of plates which were then attached to a materials testing machine. Two parallel pins were used for joint fixation; steel pin fixation was tested first in each joint. Seven scapholunate joints and seven lunotriquetral joints were each tested in three different modes: translation in two orthogonal directions, and rotation. Results. Bioabsorbable pin fixation provided an average of 46% of the stiffness of steel pin fixation. Conclusions. Although bioabsorbable pin fixation was statistically less stiff than steel pin fixation, relatively high loads were required to induce significant intercarpal joint translation and rotation.