The ball and socket implant of thumb carpometacarpal joint affects the muscle forces in lateral pinch

• Main Authors: Wei-RungLai, 賴韋戎
• Other Authors: Fong-Chin Su
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/81339861438775773082

碩士 === 國立成功大學 === 生物醫學工程學系 === 101 === Many daily activities are completed by hands such as writing, typing, using phone, etc. In these motions, thumb opposition is an important component. And the CMC joint of thumb provides the ability to do the opposition motion. But degeneration is often observed in CMC joint. It was reported that 6% of men between 55 to 64 years old were observed to have CMC degeneration, and 25% of postmenopausal women were observed to have osteoarthritis (OA) in CMC joint. Arthroplasty is necessary when severe degeneration of CMC joint was observed. The saddle type and ball-and-socket type implants are often selected in arthroplasty. But few studies compared the advantage of different types of implants. Therefore the purpose of this study is to compare these two types of CMC joints by observing the tendon forces and joint constraints. This study built up a model to simulate muscle forces of the thumb during pinching. This model was established by a customized program. The model was separated into two parts in which the CMC joints were saddle type and ball-and-socket type, respectively. There were three pinching positions, and there were two magnitudes of pinching force at each pinching position. The inputs were the relationship of bones (distal phalangeal, proximal phalangeal, metacarpal and trapezium) from CT image and pinching force measured from loadcell, and the outputs were tendon forces and joint constraints. The results showed the axial loadings in the group of ball-and-socket type of CMC joint were significant higher than those in the group of saddle type of CMC joint. The tendon force in APL also showed significant increasing in the group (ball-and-socket type of CMC joint). There were studies indicating that subsidence was often observed in ball-and-socket type implant, thus, the increasing of axial loading may explain this situation. In conclusion, the axial loading and muscle forces in the group of ball-and-socket type of CMC joint were higher than those in the group of saddle type of CMC joint.