Biomechanical Analysis of the Distal Metaphyseal Ulnar Shortening Osteotomy

Abstract

To investigate the effect of a closing wedge osteotomy at the distal ulnar metaphysis on unloading the ulnar side of the wrist. Seven fresh frozen cadaver arms mounted in a wrist simulator were used for the analysis. A 6-degrees-of-freedom load cell was mounted on the distal radius and another on the distal ulna. Radioulnar carpal joint forces and transverse distal radioulnar joint (DRUJ) load were measured at static wrist positions and during dynamic wrist motions before and after the distal metaphyseal ulnar shortening osteotomy (DMUSO) was performed. At each static position, significant decreases in ulnar load were noted after DMUSO. In addition, mean and maximum loads decreased for each dynamic wrist motion. There were no statistically significant differences in transverse forces across the DRUJ after DMUSO. This study showed that DMUSO is an effective way to decrease the load across the ulnocarpal joint. The geometry of the osteotomy and resultant change in the position of the ulnar head did not increase transverse joint reaction forces. This technique is an alternative to open diaphyseal techniques or methods that damage the articular surface of the distal ulna. Clinical studies will be necessary to associate the biomechanical correction noted in this study with clinical symptom improvement.