右立脚期に右腰背筋の疼痛を認めた筋・筋膜性腰痛症患者の一症例

－右内腹斜筋の筋活動パターンに着目して－

抄録

We encountered a patient undergoing physical therapy for myofascial lumbago. The patient complained of pain in the right dorsolumbar muscles during walking. Anteversion and leftward inclination of the pelvis (Trendelenburg's sign-like findings) were noted in the early to mid-right stance phase of walking. It was assumed that the right dorsolumbar muscles had become hyperactive, acting as a brake for the accompanying left anterior inclination of the trunk, thus producing pain. In physical therapy to resolve the Trendelenburg's sign-like findings, the right hip joint was treated with right hip extension ROM exercise and muscle strengthening exercise. The therapeutic effect was insufficient, and muscle pain in the right dorsolumbar area persisted. To identify the mechanism behind the Trendelenburg's sign-like findings in this patient, we investigated the influence of lateral body weight shift to one leg in a standing position on the internal oblique, gluteus medius, and dorsolumbar muscles in healthy subjects. The investigations measured on electromyography and the center of pressure (COP). The internal oblique muscle on the shift-to side was active from the early phase of the COP shift toward the shifted side. This was immediately followed by gluteus medius muscle activity, suggesting that stabilization of the sacroiliac joint by internal oblique muscle activity was important for resolving Trendelenburg's sign-like findings. We applied this finding to physical therapy for the patient, in which body weight was shifted rightward in a standing position to correct the activity pattern of the right internal oblique muscle. After this intervention, the right internal oblique muscle activity pattern on lateral body weight shift in a standing position and the right early to mid-stance phase of walking were corrected. The patient was able to maintain the pelvis in a horizontal position, and the Trendelenburg's sign-like findings were resolved. The intervention may have reduced the hyperactivity of the right dorsolumbar muscles associated with the leftward inclination of the trunk, thus resolving the pain. Our experience with this case suggests the importance of evaluating and performing physical therapy on internal oblique muscle activity on the shift-to side in cases showing Trendelenburg's sign-like findings.