LAUSR

Background Entrapment of the middle cluneal nerve (MCN), a peripheral nerve in the buttock, can elicit low back pain (LBP). We examined the epidemiology, clinical course, and treatment of MCN entrapment (MCN-EN). Methods Among 383 LBP patients who visited our institute, 105 were admitted for intractable LBP. They were 42 men and 63 women; their average age was 64 years. Based on clinical symptoms, palpation, and the effects of MCN block, we suspected MCN-EN in these 105 patients, 50 of whom are our study subjects. Their treatment outcomes were assessed at the time of discharge and at follow-up visits. Results MCN-EN was diagnosed in 50 of the 383 patients (13.1%) and they were hospitalized. In 43 (11.2%), MCN-EN was associated with other diseases (superior cluneal nerve entrapment, n = 21, sacroiliac joint pain, n = 9, other, n = 13). At the time of discharge, the symptoms of patients with LBP due to MCN-EN were significantly improved by repeat MCN blocks. In 7 of the 383 patients (1.8%), LBP was improved by only MCN blocks; 5 of them had reported leg symptoms in the dorsal part of the thigh. After discharge, 22 of the 50 hospitalized patients required no additional treatments after 2–5 blocks; 19 required only conservative treatment, and 9 underwent microsurgical release of the MCN. Conclusions We confirmed MCN-EN in 50 of 105 patients admitted for intractable LBP. Repeat MCN blocks were effective in 22 patients; 19 required additional conservative treatment, and 9 underwent surgery. Buttock pain radiating to the posterior thigh was an MCN-EN symptom that has been diagnosed as pseudo-sciatica. Before subjecting patients with intractable LBP to surgery, the presence of MCN-EN must be ruled out.