Ulnar Extension Coupling in Functional Wrist Kinematics During Hand Activities of Daily Living

Purpose: Wrist circumduction is increasingly used as a functional motion assessment for patients. Thus, increasing our understanding of its relation to the functional motion envelope is valuable. Previous studies have shown that the wrist is preferentially extended during hand activities of daily living (ADLs), with greater ulnar than radial deviation. The purpose of this study was to characterize the functional wrist motions of 22 modern ADLs in healthy subjects. We hypothesized that the subjects would perform ADLs predominantly in ulnar extension. Methods: Ten right-handed, healthy subjects performed flexion-extension, radioulnar deviation, maximal circumduction, and 22 modern ADLs. Angular wrist positions were obtained by tracking retroreflective markers on the hand and forearm. Angular motion data were analyzed with a custom program for peak/trough angles in flexion extension and radioulnar deviation, ellipse area of circumduction data, and ellipse area of combined motion data. Results: The required ranges of motion for ADLs were from 46.6° ± 16.5° of flexion (stirring task) to 63.8° ± 14.2° of extension (combing) in flexion-extension and from 15.6° ± 8.9° of radial deviation (opening a jar) to 32.5° ± 8.3° of ulnar deviation (picking up smartphone) in radioulnar deviation. Ellipse area of combined motion data of the 22 ADLs were, on average, 58.2% ± 14.3% of the ellipse area of maximal circumduction. A motion data quadrantal analysis revealed that 54.9% of all ADL wrist motion occurred in ulnar extension. Among the average wrist positions for 22 ADLs, 16 were located in the ulnar extension quadrant. Conclusions: This study revealed a functional wrist motion envelope that was less than 60% of wrist maximal motion capacity on average. Our results also showed that the majority of ADLs are performed in ulnar extension of the wrist. Clinical relevance: Baseline values for healthy subjects performing 22 wrist ADLs can inform future studies assessing dysfunction, postsurgical changes, and rehabilitation progress.