Pathology of the capsular and synovial hip nerves in chronic hip diseases.

Nerves of the synovial membrane and of the capsule of the hip have been studied with the usual techniques of optical neuropathology. We studied 52 hips from 46 patients: 13 hips of post-fracture states of the femoral neck, 13 hips of idiopathic osteonecrosis, 6 hips of rheumatoid arthritis, 6 hips of ankylosing spondylitis and 14 hips of osteoarthrosis. Small capsular and synovial nerves mainly located close to blood vessels are modified by the lesions of the surrounding tissue (inflammatory, vascular, traumatic and mechanical disturbances). The degree of involvement is related to the disease and its evolution. The peri- and endoneurium is thickened and demyelination is mostly observed. Nerve lesions begin focally and for some time are segmental. The final lesions correspond to a complete fibrous transformation of the nerve with loss of axons. We suggest a correlation between nerve lesions and the existence or absence of pain in the hip.