Piriformis syndrome and low back pain: a new classification and review of the literature.
Piriformis syndrome is a common cause of low back pain. It is often not included in the differential diagnosis of back, buttock, and leg pain. Additionally it has received minimal recognition because it is often seen as a diagnosis of exclusion. Familiarity with the common elements of the syndrome should increase its recognition and facilitate the appropriate treatment. These include buttock pain and tenderness with or without electrodiagnostic or neurologic signs. Pain is exacerbated in prolonged sitting. Specific physical findings are tenderness in the sciatic notch and buttock pain in flexion, adduction, and internal rotation (FADIR) of the hip. Imaging modalities are rarely helpful, but electrophysiologic studies should confirm the diagnosis, if not immediately, then certainly in a patient re-evaluation and as such should be sought persistently. Physical therapy aims at stretching the muscle and reducing the vicious cycle of pain and spasm. It is a mainstay of conservative treatment, usually enhanced by local injections. Surgery should be reserved as a last resort in case of failure of all conservative modalities. Piriformis syndrome may constitute up to 5% of cases of low back, buttock, and leg pain. Recognition and widespread appreciation of the clinical presentation improves its early detection and accurate treatment.