[The natural course of osteoarthritis of the hip. Indication of conservative treatment in relation to osteophyte formation at the acetabular rim].

One hundred and eighty-five hips from 152 patients with primary or secondary osteoarthritis were studied in an attempt to assess the degrees of hip pain in contrast to radiological and other clinical findings. In 30.8% and 26.4% of the primary and secondary osteoarthritic hips respectively, hip pain showed some gradual decrease as time elapsed. Pain relief probably in association with osteophyte formation at the craniolateral acetabular rim occurred in 62.5% and 33.3% of the primary and secondary osteoarthritic hips respectively. Significant parameters observed in the primary osteoarthritic cases of the decreasing pain group were as follows: A lesser extent of cranial displacement of the femoral head, poor capital drop development, well developed floor osteophyte. On the other hand significant parameters in the decreasing pain group of secondary osteoarthritis were as follows: Well developed floor osteophyte, a small size of cyst in both the femoral head and the acetabulum, few "b" or "d" type of bony sclerosis in the acetabulum. Careful observation of radiographic changes (cyst and sourcil) would be most important, especially in secondary osteoarthritis, to decide the indication of surgery. On the basis of histological studies of osteophyte at the craniolateral acetabular rim obtained at the operation, it was assumed that the osteophyte formation had initiated from metaplasia of the labrum or synovial membrane and progressed by a form of chondral ossification after the process of fibrous tissue formation. A well developed trabecular density in the osteophyte at the craniolateral acetabular rim was determined by the use of Muto digigrammer system, Model G-002.