非外傷性小指伸筋腱脱臼の1例

Non-Traumatic Dislocation of the Extensor Tendon of the Little Finger : Case Report

　抄録：小指総指伸筋腱が欠如し，小指伸筋腱が2本に分かれ，その2腱間の非外傷性解離により，2本の腱が屈曲時にそれぞれ橈尺側に脱臼する．その結果，2腱間から中手骨頭がボタン穴様に現れる稀な1例を報告する．51歳，男性．2年前から誘因なく，右小指に弾発現象が出現した．小指総指伸筋腱は欠如し，環指総指伸筋腱と小指伸筋腱との間に，Y字型腱が存在した．小指伸筋腱は2本に分かれ，指背腱膜の一部とその中枢付近には瘢痕組織が存在し，2本の腱間の結合は解離していた．小指を屈曲すると，2本の小指伸筋腱はそれぞれ橈尺側に脱臼し，その間から第5中手骨頭がボタン穴様に現れる．伸展すると脱臼した2本の腱は中手骨頭を背側に滑り上がり，その時小指は弾発現象を伴う．そこで2腱間を側側縫合して，3週間の外固定後リハビリテーションを開始した．術後10カ月現在，可動域制限や弾発現象もなく経過良好である．中手指節関節（以下MP関節）背側における伸筋腱の脱臼は，関節リウマチに発症するもの以外は比較的稀である．今回われわれは，小指MP関節に発症した非外傷性の伸筋腱脱臼の1例を経験し，観血的治療で良好な結果を得たので，若干の文献的考察を加え報告する．

　A 51-year-old man first complained of non-traumatic snapping in his right little finger two years previously. Examination at that time revealed that the extensor digitorum communis (EDC) Ⅴ was absent. The extensor digiti minimi (EDM) tendon was split longitudinally and connected by a Y-shaped tendon with the EDC Ⅳ. Scar tissue surrounded the EDM tendons and the expansion hood. The connection between the two EDM tendons was very loose. The tendons of the EDM subluxated to either side during flexion, and the head of the 5th metacarpal bone emerged between them like a button that had been pushed through a buttonhole. When the MPJ of the little finger was extended to 0 degrees from the flexed position, each tendon of the EDM slipped dorsally on the 5th metacarpal head, and their reduction was associated with snapping. Treatment consisted of side-to-side suturing of the tendons at the 5th MPJ. The hand was then immobilized with a splint for three weeks, after which ROM exercise was started. Ten months after the operation, the snapping phenomenon has resolved, and the patient has full range of motion of his little finger.