Piriformis syndrome: diagnosis, treatment, and outcome--a 10-year study.

Abstract

To validate an operational definition of piriformis syndrome based on prolongation of the H-reflex with hip flexion, adduction, and internal rotation (FAIR) and to assess efficacy of conservative therapy and surgery to relieve symptoms and reduce disability. Before-after trial of cohorts identified by operational definition. Outpatient departments of 2 hospitals and 4 physicians' offices. Surgery performed at 3 hospitals. Consecutive sample of 918 patients (1014 legs) with follow-up on 733. Patients with significant (3 standard deviations [SDs]) FAIR tests received injection, physical therapy, and serially reported pain and disability assessments. Forty-three patients (6.47%) had surgery. Likert pain scale. Subjective estimates of disablement in activities of daily living and instrumental activities of daily living. At 3 SDs, the FAIR test had sensitivity and specificity of.881 and.832, respectively. Seventy-nine percent (514/655) of FAIR test positive (FTP) patients improved 50% or more from injection and physical therapy at a mean follow-up of 10.2 months. Average improvement was 71.1%. Of 385 FTP patients with disability data, mean disability fell from 35.37% prestudy (SD =.2275) to 12.96% poststudy (SD =.1752), a 62.8% improvement. Twenty-eight surgical FTP patients (68.8%) showed 50% or greater improvement; mean improvement was 68% at a mean follow-up of 16 months. Surgery reduced the mean FAIR test to 1.35 +/- 2.17 months postoperatively. FTP patients generally improved 10% to 15% more than others after conservative treatment. The FAIR test correlates well with a working definition of piriformis syndrome and is a better predictor of successful physical therapy and surgery than the working definition. The FAIR test, coupled with injection and physical therapy and/or surgery, appears to be effective means to diagnose and treat piriformis syndrome.