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Quadratus Femoris muscle causing deep gluteal syndrome: A rare cause of refractory sciatica of extraspinal origin in the presence of an anatomic variation.

BACKGROUND KNOWLEDGE
Sciatica of extraspinal origin represents both a diagnostic and a therapeutic challenge for spine specialists. Among these, quadratus femoris muscle (QF) is often overlooked as a pain-generator.


REPORTED CASE
A 62-years old man was referred from general practitioner for isolated sciatica in the left leg, refractory to conservative treatments. Plain x-rays of the spine did not show any pathological finding nor did magnetic resonance imaging (MRI). MRI and CT showed QF with unusual morphologic features and agenesis of the contralateral QF. Ultrasonography-guided injection in the muscle was performed with mepivacaine and methylprednisolone obtaining relief of the symptoms.


DISCUSSION
Leg pain can be very disabling and, when combined with a normal MRI of the spine, diagnosis can be tricky. Several causes of sciatica of extraspinal origin have been described, some of them originating from the so-called "deep gluteal space". Anecdotal communications on anatomical variations of the quadratus femoris muscle are reported in literature.


CONCLUSIONS
Differential diagnosis of sciatica of extraspinal origin must rule out sacroiliac and hip joint so as deep gluteal space structures. Among these, quadratus femoris muscle is often overlooked as a pain-generator. Ultrasonography-guided intramuscular injections and a program of stretching and strengthening exercises can achieve durable control on the symptoms.