Biomechanical Effects of Radioscapholunate Fusion With Distal Scaphoidectomy and Triquetrum Excision on Dart-Throwing and Wrist Circumduction Motions

Purpose Distal scaphoid and triquetrum excisions can improve the range of wrist motion after radioscapholunate (RSL) fusion, but little is known about kinematics dart-throwing global circumduction motions. We hypothesized that these could increase without causing midcarpal instability. Methods Seven fresh-frozen cadaver upper extremities were mounted on a testing apparatus isolation preloading tendons flexor carpi radialis, ulnaris, extensor ulnaris. Sequential loadings ulnaris radialis simulated active motion. Passive circumferential loading produced measured motions with an electromagnetic tracking system in 4 experiments: intact, RSL fusion distal excision, total excisions. To evaluate stability, we conducted passive mobility carpal row radial, volar, ulnar, dorsal directions. Results Radioscapholunate decreased to mean 46% baseline value; increased arc 50% 62%, respectively. diminished 43% value, which 58% 74% A significant radial deviation was noted subsequent excision significantly ulnar-palmar direction. Regarding translation Conclusions improved both motions, instability occurred. Clinical relevance Subsequent may short-term outcome by increasing RSL-fused wrist; however, potential risk should be considered.