長母趾屈筋腱滑液包炎の1例

Bursitis around the Flexor Hallucis Longus Muscle. Case Report

　症例は関節リウマチで加療中の75歳の女性で，主訴は右後足部痛であった．DAS28 scaleは寛解状態で単純X線像上も関節裂げきは保たれていた．超音波検査・MRI検査で直径25mm程度の囊胞性病変があり，長母趾屈筋ガングリオンあるいは滑液包炎を疑った．伏臥位足関節後外側アプローチで摘出したところ症状は消失した．病理検査は内腔側にfibrinの析出を伴うfollicular bursitisであった．長母趾屈筋腱滑液包炎は稀な症例で，超音波検査が経済的かつ非侵襲的で診断に有用であった．術後8カ月で再発なく経過良好である．

　A 75-year-old woman with well controlled rheumatoid arthritis (RA) complained of posterior ankle pain when she walked.　Ultrasonography and MRI revealed a cyst arising from the muscle-tendon junction of the flexor hallucis longus (FHL) muscle.　Based on the imaging findings we considered a ganglion and bursitis in the differential diagnosis and planned open surgery.　A longituditional lateral para-Achilles-tendon skin incision was made, and a cyst was resected.　Histopathological examination showed a cystic lesion with irregular fibrous wall.　The lining of the cyst wall showed lymphoid hyperplasia and angiogenesis with lymphocytes and plasma cells.　Based on these findings, a diagnosis of follicular bursitis was made.　To our knowledge and as far as we were able to determine in a literature search, reports of bursitis around the FPL muscle have been rare.　Ultrasonography is a very useful tool for economically and less invasively detecting pathological changes in soft tissue.　As of the 8-months follow-up examination the patient has fully recovered from the posterior ankle pain, and there have been no recurrences.