Reliability of thumb web measurements

Two new methods of thumb web space measurement, the intermetacarpal distance (IMD) and the derived intermetacarpal angle (DIMA), were proposed and compared with a conventional method for interrater reliability. Forty subjects (22 normal hands, 18 impaired hands) were measured. Reliability of the measurement was estimated using the intraclass correlation coefficient (ICC) and the Bland and Altman method of 95% limits of agreement. Overall, the IMD method showed an ICC of 0.88 with 95% limits of agreement of -6.9 to 5.6 mm (approximately +/-6.2 mm). Similarly, for the DIMA method, the ICC was 0.47 with 95% limits of agreement of -11.9 to 5.1 degrees (approximately +/-8.5 degrees ). The IMD method appears more reliable than the conventional method, which had an ICC of 0.26 and 95% limits of agreement of -17.5 to 9.2 degrees (approximately +/-13.3 degrees ). The IMD method is recommended as a reliable method of measuring the thumb web space.