Natural history of radiographic hip osteoarthritis: A retrospective cohort study with 11-28 years of followup.

Abstract
OBJECTIVE:
To evaluate the association between radiographic hip osteoarthritis (OA) and future total hip replacement (THR) due to OA or hip fracture.
METHODS:
We studied a cohort of individuals who had colon radiography from 1980-1997. Minimal joint space (MJS) was measured and each hip was graded for radiographic OA according to the Kellgren/Lawrence scale. Subjects were followed until the end of 2008. A Cox proportional hazards model, adjusted for age and sex, was used to evaluate factors associated with THR and hip fracture.
RESULTS:
A total of 2,953 hips were studied (57% women). The cumulative incidence of THR was 2.5% and the cumulative incidence of hip fracture was 2.6%. For hips with radiographic hip OA (MJS of 2.5 mm or less), the cumulative incidence of THR was 16.9% and the hazard ratio (HR) for THR was 13.2 (95% confidence interval [95% CI] 8.1-21). Using Kellgren/Lawrence grading, the HR for THR was 12.9 (95% CI 7.9-21) for hips with radiographic OA compared to those without. The HR for all types of hip fracture for hips with radiographic OA (MJS of 2.5 mm or less) was 0.47 (95% CI 0.15-1.5), for intracapsular fractures was 0.29 (95% CI 0.04-2.1), and for extracapsular fractures was 0.67 (95% CI 0.16-2.8).
CONCLUSION:
The risk of THR due to OA is substantially increased in patients with radiographic hip OA, regardless of symptoms, and increases with decreasing MJS. However, 11-28 years after having had radiographic hip OA, more than 4 of 5 of those having radiographic signs of hip OA had not had a THR for OA.