Extrapelvic Compression of the Femoral Nerve: An Uncommon Cause of Hip Pain

Abstract

The case of a patient with short history of unilateral hip pain due to compression of the lumbar plexus by a cyst arising from the hip joint is reported. Radiologically there were only mild signs of osteoarthritis of the affected hip but severe degenerative changes were found in the lumbar spine. There was atrophy of the quadriceps muscle of the affected limb with subsequent giving-way during gait and sensory loss on the lateral aspect of the thigh. The neurological and electromyographical examination suggested compression of the lumbar plexus. By sonography, computerized tomography and contrast radiographs, a finger shaped cyst was identified going from the ventromedial aspect of the hip joint between the iliopsoas, the pectineus, and the iliacus muscles respectively. After excision of the cyst, hip pain ceased and the signs of neural compression disappeared almost completely within 12 weeks. Histologically the specimen showed synovial tissue with cartilaginous debris. In cases of hip pain without sufficient radiological and clinical signs of osteoarthritis, femoral nerve compression should be excluded by neurological examination. To our knowledge, this is the first report about compression of the femoral nerve by an isolated extrapelvic cyst arising from the hip joint.