To assess whether the ulnar styloid abduction angle (USAA) is an independent bony predictor of Palmer Type IB TFCC tears and to investigate its non-linear dose–response relationship and clinical predictive value.
Approach:
Study Design: Retrospective case–control study; evidence grade: Level 3.
Participants: 362 patients with strict radiographic quality control, including 110 cases of Palmer Type IB tears and 252 control cases.
Statistical Analysis: Multivariate binary logistic regression, restricted cubic spline model, Bootstrap resampling for internal validation, and decision curve analysis.
Key Findings:
The area under the receiver operating characteristic curve (AUC) after optimism-corrected AUC using bootstrap resampling was 0.849.
DCA confirmed that the USAA-based diagnostic strategy offers significant net clinical decision-making benefits across a wide range of threshold probabilities.
Interpretation:
An increased USAA is a significant radiographic predictor of Palmer Type IB TFCC tears, exhibiting a non-linear dose–response relationship with injury risk.
Conclusion:
USAA can be reliably measured on standard wrist radiographs.
