Assessment of strength of individual digits in persons with osteoarthritis of the hand

Introduction The purpose of this study was to determine the extent to which individual digit strength measures correlate with overall hand strength, pain and function in persons with osteoarthritis (OA) of the hand, and thereby judge whether individual digit strength measures are relevant to the clinical assessment of hand disability in this population. Methods One hundred and four community-dwelling persons with OA of the dominant hand (84 women) participated in this cross-sectional study. Correlations between measures of hand strength (grip: digit and total; pinch: tripod, wide key and narrow key), dexterity and self-reported pain and function (subscales of the Patient-Rated Wrist and Hand Evaluation) were investigated. Results Although OA involved radial digits more than ulnar digits, radial digit strength contributes more to total grip (59% versus 41%). Correlations between total grip and digit strength varied from excellent (digits 3 and 4: r = 0.93 and 0.88, respectively) to moderate (digits 2 and 5: r = 0.75 and 0.74, respectively). Correlations between pinch and individual digit strength (digits 2 and 3) were moderate ( r = 0.66–0.74). Correlations between measures of different constructs (strength, pain and physical function) did not exceed 0.41. Conclusions Individual digit strength is not linked with OA involvement of that digit. At most, strength of individual digits explains just over half of the variance in total grip strength and pinch strength. Assessment of individual digit grip strength appears to provide unique information regarding hand disability in persons with OA.