The Effects of Distal Pole Scaphoid Resection on Wrist Biomechanics.

Abstract

Distal pole scaphoid resection (DPSR) is an effective way to manage chronic scaphoid non-union with limited degenerative arthritis. Studies have reported positive results in terms of pain relief, wrist range of motion and grip strength, and patient satisfaction. However, the biomechanical consequences of DPSR remain unclear. This study evaluates the effects of DPSR on carpal mechanics by assessing changes in radiographic parameters with varying quantities of scaphoid removal. Six fresh frozen cadaveric upper extremities were used. Resections of 25%, 50%, and 75% of the length of each scaphoid were performed under fluoroscopic image guidance. For the intact scaphoid and each resection level, the following radiographic parameters were assessed: radiolunate and capitolunate angles; carpal height and first metacarpal subsidence ratios, and ulnar carpal translation. Measurements were then repeated for grip and pinch as well as radial and ulnar wrist deviation positions. Radial styloid to trapezium distance in wrist radial deviation was also measured to assess for impingement. There was a statistically significant increase in the mean radiolunate angle with increasing scaphoid resection quantities. No statistically significant correlations were found between radial styloid clearance and increasing scaphoid resection percentages. Changes in the remaining variables did not reach statistical significance. Increasing levels of scaphoid resection is associated with progressive signs of carpal malalignment best depicted by increasing radiolunate angles. Diminishing radial styloid clearance was clinically evident as more scaphoid was resected. For this, prophylactic radial styloidectomy may be considered to avoid bony impingement.