Trapeziometacarpal Fusion With and Without Distal Scaphoid Excision: A Cadaveric Model Comparing Thumb Range of Motion.

Abstract

Purpose: To describe the biomechanical changes seen after thumb carpometacarpal (CMC) fusion with distal scaphoid excision (DSE), a surgical technique used for pantrapezial disease in high-demand individuals. Methods: A cadaveric study with 13 fresh-frozen cadaveric specimens was conducted. Fluoroscopic measurements in posteroanterior (PA) and lateral planes were performed. Thumb CMC fusion was then simulated. The same images were taken after fusion. The distal scaphoid was excised, and the measurements were obtained again. The angle between the index finger and thumb metacarpals was recorded. Statistical analysis was performed using Wilcoxon signed rank test. Results: The mean arcs of motion in the PA plane pre-fusion, post-fusion, and post-fusion with DSE were 48.5°, 25.1°, and 34.6°, respectively. An increase in arc of 9.5° was obtained after DSE compared with thumb CMC fusion alone. The mean arcs of motion in the lateral plane pre-fusion, post-fusion, and post-fusion with DSE were 53.4°, 22.4°, and 33.6°, respectively. A statistically significant increase in arc of motion of 11.2° in the lateral plane was obtained after DSE compared with thumb CMC fusion alone. This was a 20% and 21% increase in pre-fusion range of motion in the PA and lateral planes, respectively, from fusion alone compared with fusion and DSE. Conclusions: Thumb CMC fusion combined with DSE maintains motion lost in simple CMC arthrodesis.