Piriformis syndrome: Correlation of muscle morphology with symptoms and signs

To determine the relation of symptoms and pain provocation tests to abnormal piriformis morphology among people with chronic buttock pain.

Each of 2 clinical symptoms and 2 clinical signs were compared with the abnormal morphology found on ultrasound. The pain-free side was used as an internal control.

A tertiary referral center.

A series of 27 consecutive patients (26 women, 1 man; average age, 48 y) with chronic low lumbosacral or buttock pain, who presented to a musculoskeletal clinic over a 12-month period, underwent ultrasound assessment of piriformis muscle morphology. Four patients were excluded because their body mass index was in excess of 30 kg/m 2 .

The symptomatic piriformis muscle was injected with bupivacaine after pain was assessed on a visual analog scale (VAS), using the resisted abduction test.

A 70% reduction of pain on the VAS was considered positive for pain in the piriformis muscle.

Odds ratios (ORs) and 95% confidence intervals were calculated comparing each of the signs and symptoms with normal morphology. The highest ORs were found for pain on walking up inclines (10.8), referred pain (5.3), and pain on needling the piriformis muscle (6.0).

This study did not provide a criterion standard for the diagnosis of piriformis syndrome, but it did support the syndrome as a contributing factor in chronic buttock pain and very low back pain.