An In Vitro Analysis of Ligament Reconstruction or Extension Osteotomy on Trapeziometacarpal Joint Stability and Contact Area

PurposePainful instability of the minimally osteoarthritic thumb carpometacarpal (CMC) joint can be treated successfully by either ligament reconstruction or metacarpal extension osteotomy. The purpose of this study was to measure the laxity of cadaveric thumb CMC joints and to determine the influence of ligament reconstruction and metacarpal osteotomy on joint laxity and contact area.MethodsThe baseline laxity of CMC joints from 25 fresh-frozen human cadaveric specimens (average age, 42 y; range, 18–55 y) was measured in the position of lateral pinch on a custom-designed CMC joint laxity tester. Joint laxity was measured again after 2 surgical simulations consisting of either a metacarpal extension osteotomy (at 10° and 15°) or a simulated Eaton-Littler ligament reconstruction (including total, volar, and dorsal ligament reconstructions relative to the plane of the thumbnail). Contact area between the thumb metacarpal and trapezium during testing was determined using stereophotogrammetry.ResultsThe 15° extension osteotomy significantly reduced CMC joint laxity in the radial-ulnar, dorsal-volar, pronation-supination, and distraction directions in the position of lateral pinch. The 10° osteotomy reduced laxity only in the dorsal-volar direction. The total ligament reconstruction significantly reduced joint laxity in the radial-ulnar, dorsal-volar, and pronation-supination directions. The dorsal ligament reconstruction reduced laxity in the dorsal-volar direction only; the volar ligament reconstruction reduced laxity in both dorsovolar and radioulnar directions. The 10° and 15° osteotomies produced a dorsal shift of the weighted centroid of contact on the metacarpal and trapezium, whereas the ligament reconstruction did not produce such an effect.ConclusionsIn the position of lateral pinch the 15° osteotomy and total ligament reconstruction significantly reduced laxity of the thumb CMC joint in all directions tested. The isolated dorsal or volar ligament reconstructions both reduced dorsal-volar laxity. Metacarpal extension osteotomy may stabilize the thumb CMC joint in lateral pinch to a degree similar to that of a standard ligament reconstruction.