The effect of orthoses on the kinematics of the trapeziometacarpal, scaphotrapeziotrapezoidal and radioscaphoidjoints.

The in-vivo effect of four different types of thumb and thumb-wrist orthoses on the 3D kinematics of the trapeziometacarpal (TMC), scaphotrapeziotrapezoidal (STT) and radioscaphoid joints was quantified using CT-scanning. Eighteen healthy female volunteers were recruited. The dominant hand of each subject was scanned in fourthumb and wrist positions, each in three conditions: without orthosis, with a thumb orthosis (Push Ortho and immediate fitting, IMF) and with a thumb-wrist orthosis (Ligaflex Manu and IMF). CT images were analyzed and rotations relative to the more proximal bone were expressed in a joint-specific coordinate system. Without orthosis, the largest STT rotations were observed during radioulnar deviation of the wrist and the STT range of motion (ROM) was significantly lower during wrist flexion-extension. All tested orthoses caused a significant reduction of the ROM at each joint compared to free motion. Significant differences in movement reduction were observed between prefabricated and IMF orthoses.The IMF thumb-wristoutperformed the Ligaflex Manu in terms of immobilization of the radioscaphoid joint. Additionally, the IMF thumb immobilized the TMC joint significantly better during thumb abduction and adduction than the Push Ortho. We found that different types of thumb and thumb-wrist orthotics are effective in reducing joint mobility. While this reduction tends to be higher using IMF compared to prefabricated orthoses, this effect is only significant for the radioscaphoid and TMC joint. The finding that thumb movements do not induce large STT rotations suggests that the thumb does not need to be immobilized in case of isolated STT osteoarthritis. This article is protected by copyright. All rights reserved.