慢性腰痛の原因であった中殿筋障害の1例

Chronic Low Back Pain Associated with Gluteus Medius Muscle:A Case Report

Ⅰ．はじめに

　腰痛の原因は多岐にわたり，画像検査で原因が特定できる特異的腰痛と，神経症状を伴わず原因が特定できない非特異的腰痛に大別される¹²⁾．非特異的腰痛は全腰痛の70〜90%を占めるが，なかには各種の薬物療法，ブロック療法や理学療法などの保存的治療に抵抗性を示し，日常生活に支障を来す症例も経験する^2,8,10)．今回われわれは，慢性腰痛の原因が中殿筋障害であり，外科的治療によって良好な疼痛コントロールを得られた症例を経験したため，若干の考察を加えて報告する．

　The clinical features and etiology of low back pain（LBP）and buttock pain（BuP）has been poorly understood. We report a case of long-term BuP that was successfully treated with gluteus medius muscle（GMeM）decompression under local anesthesia. A 71-year-old man was referred to our hospital because of long-term BuP and claudication. Left BuP that radiated to the left thigh was observed. The pain was mostly triggered by palpation at the middle of the iliac crest and greater trochanter. Lumbar and pelvic radiograms showed no significant lesions. Lumbar magnetic resonance imaging revealed a mild lumbar spinal canal stenosis at the L4/L5 segment. Based on the evidence of a trigger point and pain relieved after GMeM block injection, we made a diagnosis of GMeM pain. Although several GMeM block injections relieved his pain, the analgesic effect was transient and the claudication remained. Then, we decided to perform GMeM decompression. We made a 5-cm-long skin incision across the trigger point on the buttock. After confirming a wide exposure of the gluteal aponeurosis over the GMeM, we cut and opened it for sufficient GMeM decompression, and the GMeM expansion was confirmed. After surgery, his symptoms immediately improved. No evidence of recurrence was observed 6 months after his treatment. For the treatment of LBP and BuP, GMeM pain would be considered a causative factor. We report that it can be treated with a less invasive surgical technique, which would contribute to good clinical outcome.