Numerous patient-reported outcome measures are used to assess thumb and hand function, but none are specific to the trapeziometacarpal (TMC) joint. The purpose of this study was to describe and validate a TMC-specific patient-reported outcome measure: the Buffalo Score.

The Buffalo Score was compared with validated functional scores (QuickDASH, Kapandji score, Trapeziometacarpal Arthrosis Symptoms Disability (TASD) questionnaire) and with objective hand measurements (lateral pinch strength and subjective strength evaluation by number of paper folds a patient can do). Ninety-two patients with complete datasets after TMC prosthetic surgery were analyzed. Internal validity was assessed through correlations with subjective functional scores, and external validity through correlations with objective measurements.

The Buffalo Score showed a very strong positive correlation with the TASD (r = 0.895, p < 0.001) and a strong positive correlation with the QuickDASH (r = 0.776, p < 0.001). A significant negative correlation was found with the Kapandji score (r = –0.530, p < 0.001). Correlations with objective measurements were weak and non-significant (pinch strength: r = –0.148, p = 0.215; number of folds: r = –0.116, p = 0.331). Pinch strength and number of folds were strongly correlated with each other (r = 0.938).

The Buffalo Score exhibits strong construct validity when compared to established subjective functional scores, effectively capturing patient-perceived functional impairment of the thumb column. However, it does not consistently predict objective pinch strength, which should be evaluated independently. Overall, the Buffalo Score serves as a straightforward and valuable tool for clinical and postoperative assessment of trapeziometacarpal pathology.