Ligamentous and tendinous support of the pisiform: anatomic and biomechanical study

Twenty-five formalin-preserved cadaveric wrists were dissected and the relationship of the pisotriquetral joint (PTJ) and its surrounding soft tissue structures were defined. An additional 4 fresh frozen wrists were examined in longitudinal and transverse sections. These anatomical studies showed the extensor retinaculum to have a complex insertion into the pisiform, flexor carpi ulnaris, fifth metacarpal, pisometacarpal ligament, and the abductor digiti minimi muscle. A capsuloligamentous structure on the medial aspect of the pisotriquetral joint was also identified. Biomechanical testing was performed on 12 fresh cadaver wrists and the results were compared to the anatomical findings to determine the contribution of surrounding soft tissue structures to pisotriquetral joint stability. Mechanical testing showed the soft tissues around the pisotriquetral joint to be strongest proximally and distally and weakest medially. Transection of the transverse carpal ligament resulted in increased lateral motion of the pisiform, but there was no significant decrease in stiffness. This study provides insight into the etiology of pisotriquetral joint instability and dysfunction.