Early radiological changes and biological reaction of primary osteoarthrosis in the hip

We followed the natural course of primary osteoarthrosis in the hip radiologically for more than 3 years, and analyzed the biological reaction (osteoblastic and osteoclastic response) to the condition with reference to the early radiological changes. Twenty hips in 14 patients were involved in this study. The average age of the patients was 62 years, and the average follow-up period was 5.9 years. Early changes at first presentation were classified according to the site of the joint space narrowing, as upper (11 hips), lateral (6 hips), or medial type (3 hips). The biological reaction at final review was classified according to the extent of osteophytosis, as hypertrophic (7 hips), intermediate (11 hips), or atrophic type (2 hips). All but one of the 11 hips with upper-type early change showed intermediate reaction. All 6 hips with lateral-type early change showed hypertrophic reaction. Of the 3 hips with medial-type early change, 2 showed atrophic reaction. We conclude that the site of joint space narrowing in the early stage is a factor that affects the ensuing biological reaction to primary osteoarthrosis in the hip.