RESUMO
Background: 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. Methods: 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. Results: 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. Conclusion: 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.
RESUMO
Background: The goal of this study is to compare the biomechanical properties of anatomic (double-bundle) versus single-bundle reconstruction of the thumb metacarpophalangeal (MCP) joint ulnar collateral ligament (UCL) in a cadaveric model. Methods: Twelve fresh frozen cadaver hands were randomly assigned to single- or double-bundle reconstruction groups using a palmaris longus autograft and tenodesis screws. Two blinded examiners performed mechanical testing and measurements using fluoroscopic imaging. We evaluated MCP joint congruence and angle in the coronal plane at 0°, 30°, and 60° of flexion with valgus loads of 1.36 and 2.72 kg. Maximum MCP flexion and extension with a 0.45 kg load was also measured. Results: There was no significant difference between single- versus double-bundle reconstruction in ulnar congruence or MCP angle. With varying amounts of flexion, there was no significant difference in MCP valgus angle between the 2 techniques, suggesting comparable joint congruity and coronal MCP angle along the arc of thumb MCP motion. Conclusions: Single- and double-bundle UCL reconstructions of the thumb MCP joint have comparable biomechanical properties in regard to joint congruity under valgus load.
