The Effect of Proximal Row Carpectomy and Trapeziectomy on First Ray Stability: A Cadaveric Study.

Abstract

Wrist and thumb pathology can coexist leading to potential indications for proximal row carpectomy (PRC) and trapeziectomy. In this setting, the axial stability of the first ray is not known. We sought to evaluate axial subsidence of the first metacarpal in cadavers following trapeziectomy and trapeziectomy with PRC to determine the mechanical effects of the procedures performed concurrently. Eleven fresh-frozen cadaveric distal forearm specimens were used in this study. The specimens were fixed in cement and mounted to a material test system frame. A predetermined force (20 N) was applied to the thumb metacarpal to simulate forces observed with lateral pinch. Axial displacement of the thumb metacarpal was measured. The application of force was repeated following trapeziectomy on each hand and then again following PRC. Analysis was performed to compare thumb metacarpal subsidence of the 3 groups: native, trapeziectomy, and trapeziectomy with PRC. Before trapeziectomy, native cadaver specimens had an average of 5.1 ± 1.9 mm of thumb metacarpal subsidence under the material test system load (20 N), compared to 16.2 ± 3.4 mm following trapeziectomy, and 25.0 ± 5.5 mm for trapeziectomy with PRC. We observed a significant increase in thumb metacarpal subsidence following concurrent trapeziectomy with PRC when compared to trapeziectomy alone. Our results suggest that performing both operations together would lead to a substantial risk of first ray subsidence. When treating concurrent basilar thumb and wrist arthritis, it may be more effective to stage the procedures or use a form of thumb metacarpal suspension or arthrodesis.