Investigating the optimal handle diameters and thumb orthoses for individuals with chronic de Quervain's tenosynovitis - a pilot study.

Aims: The aims of this study were to compare the differences in forearm muscle activities between two types of thumb orthoses and the optimal handle diameter when the orthosis is worn during a power grasp for individuals with chronic de Quervain's Tenosynovitis. Methods: A 2 x 3 (Group x orthosis) and a 2 x 2 x 3 (Group x orthosis x diameter) repeated factorial design were used. Grip strength and muscle load were measured. A 2 x 3 mixed repeated measures ANOVA was conducted, and the Least Significant Difference (LSD) test was used for post hoc analysis. Cohen's d was used to calculate the effect size between groups and handle diameters. Results: Grip strength was significantly lower (in long/short/no-orthosis conditions) and muscle load was higher in 12 participants with chronic de Quervain's Tenosynovitis than in 16 healthy participants (p < 0.001). No differences in muscle activities were found when the two different orthoses were worn. The muscle activities were higher during grasping of the 33 mm handle diameter. Conclusion: Individuals with chronic de Quervain's Tenosynovitis require greater muscle loads than healthy controls to produce the same power grasp, and when one of the two orthoses is worn, the optimal handle diameters for performing a power grasp are relatively larger (45 and 55 mm).