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Atrophic hip osteoarthritis and osteoporotic fracture risk

DOI:10.1038/bonekey.2013.92

Atrophic hip osteoarthritis (OA) is far less well characterized than normotrophic or hypertrophic OA but it is known to involve degradation of cartilage in the absence of osteophyte formation. This study determined the bone mineral density (BMD), fracture risk and structural properties of the hip bone in patients with the three types of OA and in healthy controls.

The participants (n=5006) formed part of a large prospective and population-based cohort study (the Rotterdam Study). Baseline BMD and geometric hip data were available, as was the rate of incident fractures during 9.6 years of follow up.

Compared to controls and patients with normotrophic OA, patients with atrophic OA had lower total body BMD (6.5% and 9%, respectively) and lower skull BMD (4% and 5%, respectively). Hypertrophic OA patients had higher total body BMD and skull BMD, greater bone strength and a wider femoral neck. Fracture risk in atrophic OA patients was 50% higher than in controls, irrespective of whether an adjustment for BMD was made. No significant difference in fracture risk was noted between the patients with normotrophic or hypertrophic OA and controls.

Editor’s comment: The clear differences in fracture risk between patients in the atrophic and other OA groups were not explained by their tendency to have falls, the extent of their disability, the use of corticosteroids or their BMD scores. Atrophic OA needs to be better classified so that patients can be more appropriately treated.

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