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

Twenty-five formalin preserved cadaveric wrists were dissected and the relationship of the piso-triquetral joint 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, piso-metacarpal ligament, and the abductor digit minimi muscle. A capsulo-ligamentous structure on the medial aspect of the piso-triquetral joint was also identified. Bio-mechanical 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 piso-triquetral joint stability. Mechanical testing showed the soft tissues around the piso-triquetral 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 piso-triquetral joint instability and dysfunction.