Deep Gluteal Syndrome

Deep gluteal syndrome (DGS) is buttock pain caused by entrapment of the sciatic nerve outside the pelvis, in the deep gluteal (subgluteal) space, rather than by a lumbar disc.

It is the umbrella term; piriformis syndrome is one subtype, caused by piriformis compressing the nerve. The typical picture is deep buttock pain that is worse with sitting. Diagnosis is clinical, after more common lumbar and hip causes have been considered.

The deep gluteal space is bounded by gluteus maximus (posterior), the posterior acetabulum, hip capsule and proximal femur (anterior), the linea aspera and gluteal tuberosity (lateral), the sacrotuberous ligament (medial), the sciatic notch (superior) and the hamstring origin at the ischial tuberosity (inferior). It contains the sciatic, pudendal and posterior femoral cutaneous nerves, the inferior gluteal vessels, piriformis and the short external rotators.

Causes of sciatic nerve entrapment in the space:

• •Fibrovascular bands (the most common finding in endoscopic series)
• •Piriformis (the historical piriformis syndrome)
• •Obturator internus and gemelli
• •Ischiofemoral impingement: narrowing between the ischial tuberosity and lesser trochanter, typically with quadratus femoris oedema on MRI
• •Proximal hamstring pathology
• •Previous trauma or surgery, vascular anomalies and tumours

The Beaton-Anson classification describes 6 piriformis-sciatic nerve variants. A variant is present in about 16% of people, so a variant on its own rarely explains DGS.

Risk factors include previous trauma or hip and pelvic surgery, prolonged sitting, and sitting on a back-pocket wallet.