Piriformis syndrome

Background

Piriformis muscle in relation to sciatic nerve.

• The piriformis muscle acts as an external rotator, weak abductor, and weak flexor of the hip
• It originates from the anterior sacrum and inserts on the greater trochanter of the femur
• The sciatic nerve typically exits the greater sciatic foramen deep along the inferior surface of the piriformis muscle, but in approximately 20% of people, the sciatic nerve pierces the piriformis muscle
• Local inflammation of the piriformis can cause muscular compression or irritation of the sciatic nerve causing local or radicular pain

Clinical Features

• Pain in area of buttocks and hamstring muscles
• Worsened by sitting, climbing stairs, or squatting

Differential Diagnosis

Hip pain

Acute Trauma

• Femur fracture
  • Proximal
    • Intracapsular
      • Femoral head fracture
      • Femoral neck fracture
    • Extracapsular
      • Intertrochanteric femur fracture
      • Trochanteric femur fracture
  • Shaft
    • Mid-shaft femur fracture (all subtrochanteric)
• Hip dislocation
• Pelvic fractures
  • Acetabular pelvic fractures
  • Open book pelvic fracture
  • Straddle pelvic fracture
  • Pelvic avulsion fracture

Chronic/Atraumatic

• Hip bursitis
• Psoas abscess
• Piriformis syndrome
• Meralgia paresthetica
• Septic arthritis
  • Septic arthritis of the hip (peds)
• Obturator nerve entrapment
• Avascular necrosis of hip

Evaluation

• May have palpable, tender mass over piriformis muscle
• Consider when patient has classic signs of lumbar radiculopathy with negative provocative testing, normal neurologic exam
• Provocative testing with Freiburgs test: placing hip in extension and internal rotation, and then resisting external rotation
  • Pain or sciatic symptoms yield a positive test
• Consider XR or outpatient MRI to rule out other causes of gluteal and sacroiliac pain

Management

• Conservative
  • Avoidance of contributory activity (e.g. running, cycling, heavy lifting)
  • Physical therapy
  • NSAIDs +/- gabapentin if patient has neuropathic pain
• May benefit from referral for steroid or botulinum toxin injection

Disposition

• Outpatient