Changes in Distal Radioulnar Joint Stability With Metaphyseal Versus Diaphyseal Ulnar Shortening Osteotomies: A Biomechanical Investigation.

Abstract

Purpose: Diaphyseal ulnar shortening osteotomy (DUSO) is the gold standard operative treatment to address positive ulnar variance in the setting of ulnocarpal impaction syndrome. However, an alternative technique, the distal metaphyseal ulnar shortening osteotomy (DMUSO), has been described with good initial results. Previous biomechanical investigations have shown increased stiffness of the distal radioulnar (DRU) joint after DUSO, but the effect of DMUSO on DRU joint stiffness has not been studied. The primary aim of the study was to compare DRU joint motion after DMUSO compared to DUSO. The hypothesis was that there is no difference in stiffness of the DRU joint after DMUSO compared to DUSO.

Methods: Twelve fresh frozen cadaveric specimens were used; six underwent DUSO, and six underwent DMUSO. A custom jig was designed and used to apply a volar and dorsal force to the distal ulnar shaft while stabilizing the carpus. Each specimen was tested before and after osteotomy in neutral rotation, 60° of forearm pronation, and 60° of forearm supination. DRU joint translation and stiffness were then compared between DUSO and DMUSO.

Results: In neutral forearm rotation, there was a significant decrease in translation of the ulna after DUSO compared to DMUSO in both volar and dorsal directions. In supination, there was a significant decrease in translation of the ulna with a volar force after DUSO compared to DMUSO. No significant differences were seen in pronation.

Conclusions: The results demonstrate that compared to DUSO, the DRU joints has more translation after DMUSO with the forearm in neutral and supination.

Clinical relevance: The authors recommend consideration of using a DUSO if there is preoperative DRU joint laxity and, alternatively, a DMUSO if no instability exists. More studies may be helpful comparing the techniques, including in vivo applications.