Prevalence of piriformis syndrome in chronic low back pain patients. A clinical diagnosis with modified FAIR test.

PURPOSE: Piriformis syndrome is a collection of symptoms and signs of pain from piriformis muscle and is characterized by pain in buttock with variable involvement of sciatic nerve. This syndrome is often overlooked in clinical practice because its presentation has similarities with other spine pathologies. A major problem with the clinical diagnosis of piriformis syndrome is the lack of consistent objective findings and an absence of single test that is specific for piriformis syndrome. Therefore, a precise and reliable clinical method of diagnosing piriformis syndrome should be developed by clinicians.
METHODS: This is a prospective observational study involving 93 consecutive patients who attended the pain management unit for chronic low back pain. The diagnosis of piriformis syndrome was made using the modified flexion adduction internal rotation (FAIR) test, which is a combination of Lasègue sign and FAIR test. Prevalence of piriformis syndrome based on this technique was compared with the previous data using other techniques. Chi square (χ2) analysis was performed to detect the relationship between piriformis syndrome and the potential risk factors.
RESULTS: On the basics of our diagnostic criteria, the prevalence of piriformis syndrome was 17.2% among low back pain patients. All the patients diagnosed with piriformis syndrome responded well with piriformis muscle injections. No significant associations were detected between piriformis syndrome and spine disorders.
CONCLUSIONS: Piriformis syndrome is a painful condition that is often overlooked in the differential diagnosis of chronic buttock or low back pain. The modified FAIR test together with piriformis muscle injection is potentially a reliable method for the clinical diagnosis of piriformis syndrome.