Contralateral hand function score for assessment after claw hand correction: Initial validation of a composite clinical outcome measure

Background Outcome assessment after claw hand correction is inconsistent, with prior reports relying on heterogeneous combinations of joint-angle measurements, photographs, grip testing, and qualitative functional grading. We developed the Contralateral Hand Function Score (CHFS), a simple contralateral hand–referenced composite measure, and evaluated its reproducibility and construct validity. Methods We performed a retrospective study of 51 patients who underwent surgical correction of claw hand between 2009 and 2025. CHFS was calculated as the mean of three equally weighted domains—motion, strength, and function—each expressed as a percentage of the contralateral normal hand. A separate modifier system (CHFS-M) recorded claw-specific contextual determinants of residual impairment but was not included in score calculation. Validation included interobserver reproducibility, interdomain coherence, and predefined known-group comparisons. Cohort characteristics, outcome distribution, and validation metrics were summarized from the study dataset. Results Mean age was 41.8 ± 12.6 years and mean follow-up was 18.6 ± 7.2 months. Mean CHFS was 66.2 ± 18.4%, with 24% excellent, 55% good, and 21% poor outcomes. Interobserver reproducibility was excellent for the final CHFS (intraclass correlation coefficient, 0.994) and for all component domains (>0.97). Cronbach’s alpha was 0.984 for the three domains and 0.932 for the function subitems. CHFS differed significantly by claw type, contracture status, and surgical technique. The most frequent contextual determinants were diminished workspace (42%), arch reversal (38%), thumb pinch deficit (34%), and flexor digitorum profundus weakness (30%). Conclusions CHFS is a simple, reproducible, and clinically interpretable outcome measure for claw hand correction. It provides a practical contralateral-referenced summary of recovery, whereas CHFS-M improves clinical interpretation by documenting residual contextual deficits not captured by the composite score alone. Level of evidence Therapeutic Level IV.