Piriformis Injection

Piriformis syndrome is a common cause of buttock and posterior leg pain. Pain in these areas can begin spontaneously or after an injury. The symptoms are commonly seen in patients with other inflammatory conditions and in patients who sit for most of their work day.

The pain usually begins when the piriformis muscle becomes taut, tender, and contracted. This process causes a deep aching sensation in the midgluteal region that is sometimes associated with pain radiating down the posterior leg or up to the lower back. The tight piriformis may cause a nerve and vessel entrapment syndrome as a consequence of its close proximity to the sciatic nerve and surrounding vessels.

Piriformis syndrome may constitute as many as 6-8% of low back pain conditions associated with sciatica. ^[1] Some patients experience symptoms in all five toes (multiple dermatomes) rather than in either lateral toes (S1 radiculopathy) or medial toes (L5 radiculopathy), as is generally the case in patients with herniated lumbar discs. The straight-leg raise (SLR) test is generally negative. Pain in the gluteal area is the predominant symptom. Numbness or weakness is rare. ^[2]

Piriformis syndrome is frequently a diagnosis of exclusion. Before the diagnosis is made, other causes of gluteal, hip, and leg pain must be ruled out (see Periprocedural Care). Michel et al created a 12-point clinical scoring system for standardization of the diagnosis and development of a treatment plan for piriformis syndrome. ^[3]

Many forms of therapy, medication, and injections have been used effectively to alleviate the pain associated with piriformis syndrome. This topic describes the most commonly piriform injection techniques (see Technique). ^[4]

Patients who do not improve with a conservative regimen of piriformis stretching, physical therapy, and administration of nonsteroidal anti-inflammatory drugs (NSAIDs) or other analgesics are candidates for piriformis injection. ^[5]

Contraindications for piriformis injection include the following:

• Local infection
• Bleeding disorders

Anatomy

The piriformis exits the pelvis through the greater sciatic foramen and inserts on the greater trochanter of the femur. The obturator internus exits the pelvis by passing through the lesser sciatic foramen; it also inserts on the greater trochanter of the femur. Both muscles assist in the external rotation and abduction of the thigh. ^[6]

The primary symptom of piriformis syndrome is buttock pain, with or without posterior thigh pain, that is aggravated by sitting or activity. Associated low back pain is common and can be a result of piriformis pain, but it can also suggest the involvement of other structures, such as facet joints or iliopsoas muscles. In an isolated piriformis syndrome, the major findings include buttock tenderness from the sacrum to the greater trochanter and reproduction of buttock pain on prolonged hip flexion, adduction, and internal rotation. ^[7]

Pain is often referred down the posterior portion of the leg, following the distribution of the tibial and peroneal branches of the sciatic nerve. These branches become inflamed as they pass over, under, or through the tight piriformis. Pain is thought to be caused by myotendinous breakdown of the piriformis, as well as by focal demyelination of the affected branches of the sciatic nerve.

The piriformis is usually tight and contracted, with focal trigger-point tenderness on palpation. Piriformis syndrome is frequently associated with sacroiliac dysfunction and leg length discrepancies.

Best practices

To decrease bruising and hematoma formation, the patient should be asked to stop taking NSAIDs (eg, ibuprofen and naproxen) 5 days before the procedure, if possible. This is helpful but not required.

For the best long-term relief, piriformis injection should be followed by a month of physical therapy (see Piriformis Syndrome).

Complication prevention

Sciatic injury can be largely avoided by advancing the needle slowly and asking the patient to report any tingling, numbness, electrical sensations, or pain down the back of the leg. At the first signs of discomfort, the needle should be pulled back and then redirected laterally. Injecting in the outer third of the muscle also lowers the chance of sciatic nerve injury.