Over-the-Top Foveal Triangular Fibrocartilage Complex Repairs With Distal Radioulnar Joint Instability: A Biomechanical Study.

Purpose: The triangular fibrocartilage complex (TFCC) is the primary stabilizer of the distal radioulnar joint (DRUJ). Injury to the TFCC's foveal insertion can cause ulnar-sided wrist pain and DRUJ instability. The aim of this study was to assess DRUJ stability, as measured by volar-dorsal translation, after TFCC foveal repair using an arthroscopic "over-the-top" technique.

Methods: After obtaining institutional biospecimens approval, eight fresh-frozen cadavers were procured. Distal radioulnar joint instability was defined as an increase in sagittal translation of the distal ulna relative to the radius. A custom biomechanical testing protocol was implemented, which involved applying a linear translation to the radius and measuring both the applied force and bone displacement in the dorsal-volar direction. The stability of the DRUJ was tested with an intact foveal insertion and ulnar styloid insertion, after release of the entire TFCC foveal insertion and transection of the superficial TFCC attachment to the ulnar styloid, and then after the "over-the-top" technique repair with three different suture configurations. Distal radioulnar joint stability was assessed in the following three wrist positions: neutral, 60° pronation, and 60° supination using both translation and stability improvement as outcomes.

Results: Distal radioulnar joint translation increased between the intact and injured conditions in neutral, pronation, and supination. Suture repair improved DRUJ translation compared with the injured state. Percent stability improvement, calculated relative to the injured condition, was higher across all repair groups. A single suture repair restored approximately half the stability relative to the injured condition, whereas the three-suture repair demonstrated the greatest improvement in DRUJ stability.

Conclusions: "Over-the-top" TFCC foveal repairs can enhance postoperative DRUJ stability.

Clinical relevance: "Over-the-top" TFCC foveal repair using three sutures provides the greatest improvement in DRUJ stability in a cadaveric model. These findings may help guide surgical decision-making regarding the optimal number of sutures needed to restore DRUJ stability following foveal TFCC injuries.