The scaphotrapezio-trapezoidal joint. Part 1: An anatomic and radiographic study.

To evaluate anatomic variations and distribution of degenerative changes in the scaphotrapezio-trapezoidal (STT) joint, 165 embalmed cadaver wrists were examined. An interfacet ridge on the distal scaphoid was found in 81% of the wrists and the shape of the distal joint surface of the scaphoid was classified into 3 types. Underdevelopment of the capitate-trapezium ligament was found in 15% of the wrists. A new skeletal measurement for the inclination of the joint surface of the trapezium-trapezoid in the STT joint (TT inclination) was investigated anatomically and radiographically. Degenerative changes were found in 39% of the wrists. The most common location of degenerative changes was on its ulnar aspect on the distal scaphoid and on the radial and central aspect of the trapezoid on the TT side. The presence of degenerative changes had a significant correlation with a higher anatomic and/or radiographic TT inclination and/or underdevelopment of the capitate-trapezium ligament.