Optimization design of thumbspica splint using finite element method.

De Quervain's tenosynovitis is often observed on repetitive flexion of the thumb. In the clinical setting, the conservative treatment is usually an applied thumbspica splint to immobilize the thumb. However, the traditional thumbspica splint is bulky and heavy. Thus, this study used the finite element (FE) method to remove redundant material in order to reduce the splint's weight and increase ventilation. An FE model of a thumbspica splint was constructed using ANSYS9.0 software. A maximum lateral thumb pinch force of 98 N was used as the input loading condition for the FE model. This study implemented topology optimization and design optimization to seek the optimal thickness and shape of the splint. This new design was manufactured and compared with the traditional thumbspica splint. Ten thumbspica splints were tested in a materials testing system, and statistically analyzed using an independent t test. The optimal thickness of the thumbspica splint was 3.2 mm. The new design is not significantly different from the traditional splint in the immobilization effect. However, the volume of this new design has been reduced by about 35%. This study produced a new thumbspica splint shape with less volume, but had a similar immobilization effect compared to the traditional shape. In a clinical setting, this result can be used by the occupational therapist as a reference for manufacturing lighter thumbspica splints for patients with de Quervain's tenosynovitis.