Maximum Palmar Abduction Angle of the Trapeziometacarpal Joint in Healthy Subjects Can Be Evaluated Accurately Using a Radiograph-Based Measurement Technique.

Abstract

In carpal tunnel syndrome, the abductor pollicis brevis, which is the primary muscle for the palmar abduction of the thumb, is almost inevitably impaired. The active palmar abduction of the thumb may be a better indicator of thumb disability. The authors aimed to establish a simple and accurate method to measure the angle of active palmar abduction of the thumb and to determine the maximum angle values in healthy women. Twenty-five women 20 to 21 years old with no disorder of the hand participated in this study voluntarily. Three measurement methods were tested. The first method was designed according to the Japanese Orthopaedic Association and the second method was designed according to the American Society of Hand Therapists; both use photographs to perform measurement calculations. In the third method, 2 orthopedic surgeons measured the same angle as that described in the second method on hand radiographs. Intra- and interobserver reliability were assessed for each method and described as interclass correlation coefficients. The first and third methods had strong inter- and intraobserver reliability. The second method had strong intraobserver reliability but medium interobserver reliability. The measurement obtained with the first method was significantly different from the values obtained by the second and third methods (almost double). Therefore, the authors regarded the third method as the most appropriate approach for measuring active palmar abduction of the thumb, which, in healthy individuals, yielded maximum values of 45.3°±6.4° and 44°±7° for the left hand and the right hand, respectively. [Orthopedics. 2020; 43(2):e95-e101.].