The purpose of this study was to evaluate the necessity of an additional dorsal fibrocartilage (DFC) repair in combined radial collateral ligament (RCL) and DFC injuries of the thumb metacarpophalangeal joint (MPJ). Eight cadaveric thumbs were used. Ulnar/radial deviation, prosupination, and volar/dorsal laxity were measured. Serial sectioning was performed of the RCL and the DFC. The RCL followed by the DFC were then reattached sequentially. Measurements were performed for intact, RCL cut, RCL+DFC cut, RCL repair alone, and RCL+DFC repair. The neutral position shifted ulnarly, pronated, and subluxed volarly after RCL+DFC cut. Volar subluxation was reduced with RCL+DFC repair compared with RCL repair alone. With external loading, ulnar deviation, pronation, and volar laxity increased significantly after RCL+DFC cut. Ulnar deviation reduced significantly with RCL+DFC repair (12.4°, 10.8°, and 10.9°) compared with RCL repair alone (14.4°, 14.3°, and 18.9°) at 0°, 30°, and 60°, respectively. Pronation reduced significantly with RCL+DFC repair (7.1° and 9.4°) compared with RCL repair alone (10.2° and 12.6°) at 0° and 30°, respectively. Volar subluxation reduced significantly with RCL+DFC repair (0.9 mm and 1.2 mm) compared with RCL repair alone (2.1 mm and 1.8 mm) at 30°and 60°, respectively. Radial collateral ligament repair alone does not restore anatomic dorsoradial stability of the thumb MPJ in a combined RCL and DFC injury. Combined repair of the RCL and the DFC is recommended to reduce the MPJ to its native position and minimize postoperative laxity. [Orthopedics. 2019; 42(2):e268-e272.].
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