Original ResearchCombined Thumb Abduction and Index Finger Extension Strength: A Comparison of Older Adults With and Without Thumb Carpometacarpal Osteoarthritis

ObjectiveThe objectives of this study were to compare thumb combined abduction/index finger extension (hand opening) strength between subjects with carpometacarpal (CMC) osteoarthritis (OA) and normal controls and to assess the reproducibility of hand opening strength and abduction range of motion (ROM) measurements in patients with thumb CMC OA to establish the cutoff values scores for minimal detectable change.MethodsSeventy-seven subjects, 96% female (age, 77 ± 7 years), participated in the study. The CMC OA group consisted of 39 patients (mean ± SD, 81 ± 7) and 38 healthy subjects (mean ± SD, 78 ± 6). Mixed models analysis of variance was conducted to determine the differences between groups.ResultsThe post hoc testing revealed statistically significant differences in pain pressure threshold, opening strength, and ROM measurements within the CMC OA group as compared with the healthy group (all, P < .01) in the dominant right hand. The average measure of CMC OA in the right hand did differ from that of the left hand for opening strength and abduction measurements. No statistical differences were revealed between groups nondominant left (all, P > .05), except in case of opening strength (P < .001). There was also large effect size between the means of the Disabilities of the Arm, Shoulder, and Hand scores between the healthy group and the CMC OA group of 1.17 (confidence interval, 1.19-2.14).ConclusionSubjects with CMC OA exhibited decreased combined thumb abduction and index finger extension strength, reduced thumb abduction ROM, and increased pain sensitivity when compared with their healthy counterparts. The minimal detectable change score in this patient population was 0.23 to 0.25 kg/cm2 for pain pressure threshold, 0.12 to 0.13 lb for opening force, and 1.24° to 1.46° for abduction ROM measurement.