Of patients presenting to pain clinics, complaints are of low back or buttock pain
with or without radicular leg symptoms is one of the most common. Piriformis
syndrome may be a contributor in up to 8% of these patients. The mainstay of
treatment is conservative management with physical therapy, anti-inflammatory medications, muscle relaxants, and correction of biomechanical abnormalities.
However, in recalcitrant cases, a piriformis injection of anesthetic and/or corticosteroids may be considered. Because of its small size, proximity to neurovascular
structures, and deep location, the piriformis muscle is often injected with the use
of commuted tomography (CT), magnetic resonance imaging (MRI), ultrasound
(US), fluoroscopy, electrical stimulators, or electromyography (EMG). Numerous
techniques have been proposed using one or a combination of the above modalities. However, application of these techniques is limited by unavailability of CT,
MRI, and EMG equipment as well as a paucity of trained physicians in US-guided
procedures in many pain treatment centers throughout the United States. Fluoroscopy, however, is more widely available in this setting.
This study utilized a cadaveric specimen to confirm proper needle placement for
piriformis or peri-sciatic injection utilizing the previously documented landmarks
for fluoroscopic guidance as described by Betts. An anteroposterior of the pelvis
with inclusion of the acetabular region of the hip and the inferior aspect of the
sacroiliac joint was obtained. The most superior-lateral aspect of the acetabulum
and the inferior aspect of the sacroiliac joint were identified. A marker was placed
one-third of the distance from the acetabular location to the inferior sacroiliac
joint, indicating the target location. A 22-gauge, 3.5-inch spinal needle was directed through the gluteal muscles to the target location using intermittent fluoroscopic guidance. The posterior ileum was contacted and the needle was withdrawn 1 –2 mm. This approach found the needle within the piriformis muscle
belly 2 –3 cm lateral to sciatic nerve. The present study was the first study, to our
knowledge, that has confirmed the intramuscular position of the needle within
the piriformis muscle of a cadaveric specimen using these anatomic landmarks
and fluoroscopic guidance.
Key words: piriformis syndrome, back pain, fluoroscopy, sciatica
Practice Patterns of Dentist Anesthesiologists in North America