Increased bone mineral content and bone size in the femoral neck of men with hip osteoarthritis.

OBJECTIVES Even though clinical findings support the idea that hip osteoarthritis (OA) is associated with increased bone mineral density (BMD), the subject remains controversial. This study was therefore initiated to investigate the relation between the severity of hip OA and femoral and calcaneal BMD. METHODS On the basis of the American College of Rheumatology criteria on classification of OA of the hip, 27 men (aged 47-64 years) with unilateral or bilateral hip OA and 30 age matched randomly selected healthy men were studied. Plain radiographs were graded using Li's scale from 0 (no OA) to 4 (severe OA). According to the side of the highest radiographic score from the patients with clinical hip OA, 29.6% had grade 1, 29.6% grade 2, and 40.8% grade 3 OA. Bone mineral content (BMC), areal BMD (BMD(areal)), and bone dimensions (area and width) were measured by dual x ray absorptiometry at the proximal femur. BMD(areal) of the calcaneus was measured from the central area of the bone. Volumetric measurements from magnetic resonance images of the femoral neck were used to create a BMD measure that was corrected for the femoral neck volume (BMD(mri)). RESULTS There were no differences in weight, or body mass index between the study groups. There were no significant BMD(areal) differences in any of the subregions of the proximal femur (femoral neck and trochanter) or calcaneus between the OA and control groups. Neither did the BMD(mri) of the femoral neck differ between the groups. However, the BMC of the femoral neck was 18% higher (p<0.01) in patients with OA than in controls. Similarly femoral neck bone width and volume were 9% and 18% respectively higher (p<0.001) in patients with OA. CONCLUSIONS The results suggest that men with hip OA have larger femoral neck size and consequently higher BMC than healthy controls matched for age and sex. There is no significant difference in femoral neck BMD (BMD(areal) or BMD(mri)) between the groups. Furthermore, increased BMD(areal) was not found in the peripheral skeleton. These findings suggest that hip OA is not associated with an increase in BMD(areal) in the femoral neck. However, the increase in BMC and bone size in patients with hip OA may play a part in the pathogenesis of the disease.