Piriformis Syndrome

• Synonyms: deep gluteal syndrome
• ICD-9= 355.0 (lesion of sciatic nerve)
• Extrapelvic sciatic sciatic nerve compression in the area of the greater sciatic notch of the pelvis.
• Post-traumtic piriformis syndrome is associated with blunt trauma to the buttock

Piriformis Syndrome Anatomy

• Thought to result from compression of the sciatic nerve, gluteal nerves, posterior femoral cutaneous nerve or pudendal nerve by the piriformis muscle or by obturator internus/gemelli

Piriformis Syndrome Clinical Evaluation

• Symptoms are non-specific
• Pain/dysethesias in gluteal region +/- radiation into hip/posterior thigh/down leg
• +/- history of trauma
• May have buttock or thigh pain as only symptom
• tenderness in sciatic notch
• Flexion, adduction, and internal rotation exacerbates symptoms
• palpable tender mass over piriformis if present is pathognomonic (Robinson DR, Am J Surg 1947;73:355)
• Lasegue's sign: pain in the vacinity of the greater sciatic notch with extension of the knee with the hip flexed to 90 degrees and tenderness to palpation of the greater sciatic notch
• Frieberg's sign: pain with passive internal rotation of the hip
• Pace's sign: pain and weakness in association with resisted abduction and external rotation of the affected thigh. (Pace JB, Western J Med 1976;124:435)
• may have intolerance to sitting

Piriformis Syndrome Xray

• A/P pelvis, A/P and lateral of affected hip will be normal
• MRI is useful to r/o other diagnoses and should be normal
• CT may show asymmetrical enlargement of the piriformis muscle. (Jankiewicz, JJ Clin Orthop 1991;262:205)
• EMG/NCV can document nerve impingement. Often normal at rest, but become abnormal with hip flexion/IR (Fishman L Arch Phys Med Rehabil 1992;73:359)
• Diagnosis can be confirm by fluoroscopic or electomyographic assisted anesthetic injections immediately alleviating symptoms

Piriformis Syndrome Differential Diagnosis

• Herniated disc
• Low back pain
• hip arthritis
• labral tear
• stress fracture
• snapping hip syndrome
• also see Ataumatic Hip Pain DDx

Piriformis Syndrome Classification / Treatment

• Rest, NSAIDs, muscle relaxants, physical therapy aimed at stretching the piriformis and short external rotators
• Consider piriformis anesthetic/corticosteroid injection
• Surgery = sectionoing piriformis at its origin, release of any fibrous bands and external sciatic neurolysis (Benson ER, JBJS 1999;81A:941)

Piriformis Syndrome Complications

• Sciatic nerve palsy
• Vascular injury
• Infection
• Hematoma

Piriformis Syndrome References

• Fishman L, Dombi G, Michealsen C, et al: Piriformis syndrome: Diagnosis, treatment, and outcome.  A 10 year study; Arch Phys Med Rehabil 2002;83:295-301