熱可塑性ニット素材で作製した母指CM関節症に対する新しい機能的装具の実践

Clinical utility of a new functional splint made of thermoplastic knit material for thumb carpometacarpal osteoarthritis

要旨：母指CM関節症に対する装具として，Kitasato Thumb Splint（以下，KTS）を考案し，母指CM関節症の2症例に対しKTSの効果を評価した．X線透視下の観察では，KTS装着下のつまみ時にCM関節の亜脱臼が整復される方向に力が働き，CM関節が安定した．KTS装着3ヵ月後には疼痛やHand 20の改善を認めた．KTSのメカニズムとして，つまみ時に第1中手骨から装具へ伝わる力が，CM関節を中心とした三点支持固定により，CM関節の亜脱臼を整復する方向に働くことが考えられた．KTSは従来の母指MP-CM関節固定装具と異なり，関節運動を許容し，痛みなどの症状を改善する機能的な装具と期待できる．

　Splints for carpometacarpal (CM) joint osteoarthritis are designed to reduce joint inflammation by stabilizing both CM and MP joints. We have developed a new type of splint, the Kitasato Thumb Splint (KTS), which corrects the position of the CM joint while keeping the MP joint mobile. KTS is made of low-temperature thermoplastic material, and made by occupational therapists to correct dislocation and/or deformation of the CM joint. The KTS is unique in that it draws the first metacarpal bone toward radius, stabilizes the thumb in an abducted position, and does not fix proximal phalanges, allowing the MP joint to extend fully. To evaluate the effectiveness of KTS, two hands with CM joint osteoarthritis (Eaton stage I, III) were X-rayed to compare the thumb extension and pinch with and without KTS. Without KTS, subluxation of the CM joint and overextension of the MP joint were observed at the resting position, and subluxation was even worse at thumb abduction and pinch movement. However, with KTS, subluxation was corrected and the overextension of the MP joint decreased at the resting position, as well as during thumb flexion/extension and pinch movement. KTS was shown to be a unique orthosis allowing MP joint movement and correcting CM joint alignment even during movement.