Adult hip dysplasia and osteoarthritis. Studies in radiology and clinical epidemiology.

Osteoarthritis (OA) presupposes the interaction of systemic and/or local factors. In hip joint OA, congenital or developmental malformation is believed to constitute an individual risk factor for premature degeneration. Hip dysplasia (HD) is such a malformation. The radiological and epidemiological studies had several aims: To critically evaluate the radiological source material of the Copenhagen Heart Study: The Osteoarthritis Substudy, consisting of 4,151 standardized, weight bearing pelvic radiographs recorded 1991-1994. To qualify or disqualify the radiological source material for further studies. To develop a comprehensible and reproducible radiographic discriminator of hip OA with as close an association to self reported hip pain as possible. To identify prevalences of hip OA and HD in a Caucasian, urban background population and investigate the influence of sex, age, physical and occupational parameters on these prevalences. To evaluate the influence of HD on hip OA development relative to other potential risk factors. To evaluate degeneration in dysplastic hips over time. To evaluate the three dimensional anatomy of HD and the distribution of degenerative features in severely dysplastic hips, and To evaluate risk factors for total hip replacement surgery. In the course of the studies we found that assessments of classic indices of HD were significantly influenced by pelvic orientation during x-ray recording and identified exclusion limits of rotation and inclination/reclination of pelvic radiographs to stay inside a measurement error of +/- 3 degrees. We found that minimum joint space width (JSW) </= 2.mm constituted a radiologic hip OA discriminator of superior reproducibility and clinical relevance compared to composite, radiological OA classifications. We documented a progressive postmenopausal decline in female minimum JSW, while male minimum JSW remained relatively unaltered throughout life. We found no evidence that smoking, occupational exposure to repeated, heavy lifting or overweight significantly influenced minimum JSW. Prevalences of hip OA was approximately 5.5% in subjects >/= 60 years of age, and HD prevalence was 4-10%, depending on the radiographic criteria applied. Age and HD were significant risk factors for hip OA development in women, and HD was found to be a significant risk factor for hip OA in men. However, only obesity was found to determine an event of hip replacement surgery. In a longitudinal study of 81 subjects and with mild or moderate hip dysplasia followed for a decade we did not document a tendency for radiological degeneration compared to 136 control subjects. In a computerized tomographic study of severely dysplastic hips we found a close relationship between insufficient anterior, acetabular containment and proximal femoral anteversion. The primary area of degeneration in dysplastic hips was in the antero-lateral quadrant of the joint.