Piriformis muscle syndrome: diagnostic criteria and treatment of a monocentric series of 250 patients.

OBJECTIVES: Piriformis Muscle Syndrome (PMS) is caused by sciatic nerve compression in the infrapiriformis canal. However, the pathology is poorly understood and difficult to diagnose. This study aimed to devise a clinical assessment score for PMS diagnosis and to develop a treatment strategy.

MATERIAL AND METHODS: Two hundred and fifty patients versus 30 control patients with disco-radicular conflict, plus 30 healthy control subjects were enrolled. A range of tests was used to produce a diagnostic score for PMS and an optimum treatment strategy was proposed.

RESULTS: A 12-point clinical scoring system was devised and a diagnosis of PMS was considered 'probable' when greater or equal to 8. Sensitivity and specificity of the score were 96.4% and 100%, respectively, while the positive predictive value was 100% and negative predictive value was 86.9%. Combined medication and rehabilitation treatments had a cure rate of 51.2%. Hundred and twenty-two patients (48.8%) were unresponsive to treatment and received OnabotulinumtoxinA. Visual Analogue Scale (VAS) results were 'Very good/Good' in 77%, 'Average' in 7.4% and 'Poor' in 15.6%. Fifteen of 19 patients unresponsive to treatment underwent surgery with 'Very good/Good' results in 12 cases.

CONCLUSIONS: The proposed evaluation score may facilitate PMS diagnosis and treatment standardisation. Rehabilitation has a major role associated in half of the cases with botulinum toxin injections.