Discrepancy in bone mineral densities at different skeletal sites in hip osteoarthritis patients

Increased femoral neck bone mineral density (BMD) in a hip with osteoarthritis (OA) has been previously reported, however, it is possible that increased BMD at sites other than the hip joint is influenced by the disease process of OA. Therefore, we measured BMD at locations different from the hip joint and determined whether higher BMD was also observed at these different skeletal sites in hip OA patients.

We measured BMD in 68 women (average age 61.0 years) scheduled to undergo total hip arthroplasty for end-stage OA and 100 healthy women (average age 60.9 years) as age-matched controls. BMD at the lumbar spine, radius, and calcaneus was measured by dual-energy X-ray absorptiometry (DXA). Moreover, we measured speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index of the calcaneus by quantitative ultrasonography (QUS).

BMD obtained by DXA at the lumbar spine and radius was significantly higher in hip OA patients than in controls. However, at the calcaneus, no significant differences were observed between the groups in BMD obtained by DXA. SOS, BUA, and stiffness index obtained by QUS were significantly lower in the OA group than in controls.

Higher BMDs of the spine and radius suggest that the incidence of osteoporosis is inversely associated with the incidence of OA. However, it remains unclear whether lack of difference in BMD and lower SOS, BUA, and stiffness index of the calcaneus in the OA group was secondary to the effect walking disturbance resulting from hip pain. Our data suggest that hip OA patients have higher BMD than healthy women, and that inactivity or immobilization caused by hip OA may reduce BMD in the lower limb.