Bone mineral density in patients with hand osteoarthritis compared to population controls and patients with rheumatoid arthritis

Objectives

Several studies have revealed increased bone mineral density (BMD) in patients with knee or hip osteoarthritis, but few studies have addressed this issue in hand osteoarthritis (HOA). The aims of this study were to compare BMD levels and frequency of osteoporosis between female patients with HOA, rheumatoid arthritis (RA) and controls aged 50–70?years, and to explore possible relationships between BMD and disease characteristics in patients with HOA.

Methods

190 HOA and 194 RA patients were recruited from the respective disease registers in Oslo, and 122 controls were selected from the population register of Oslo. All participants underwent BMD measurements of femoral neck, total hip and lumbar spine (dual‐energy x ray absorptiometry), interview, clinical joint examination and completed self‐reported questionnaires.

Results

Age‐, weight‐ and height‐adjusted BMD values were significantly higher in HOA versus RA and controls, the latter only significant for femoral neck and lumbar spine. The frequency of osteoporosis was not significantly different between HOA and controls, but significantly lower in HOA versus RA. Adjusted BMD values did not differ between HOA patients with and without knee OA, and significant associations between BMD levels and symptom duration or disease measures were not observed.

Conclusion

HOA patients have a higher BMD than population‐based controls, and this seems not to be limited to patients with involvement of larger joints. The lack of correlation between BMD and disease duration or severity does not support the hypothesis that higher BMD is a consequence of the disease itself.Osteoporosis is recognised as a frequent complication to rheumatoid arthritis (RA).¹ Osteoarthritis (OA) is the most frequent rheumatic joint disease, and contrary to the situation in RA, several studies have revealed increased bone mineral density (BMD) in patients with knee or hip OA, even if the results have not been consistent in all studies.^{2,3,4,5,6,7,8,9,10} The hand is a frequent site of peripheral joint involvement in OA. However, a limited number of studies have addressed the issue of osteoporosis in hand osteoarthritis (HOA), and the results from these few studies have been inconsistent regarding levels of BMD compared with controls.^{8,9,10,11,12,13,14,15}OA has generally been considered as a cartilage disease characterised by slow progressive degeneration of articular cartilage due to “wear and tear” mechanisms. However, there is increasing evidence that abnormalities in the subchondral bone and systemic factors may contribute to the pathophysiological process. Studies of subchondral bone have revealed alterations in microstructure including increased BMD. This local increase in BMD in OA joints may be a consequence of reduced shock absorption in joints with degenerated cartilage,⁵ or on the contrary, thickening and stiffening of the subchondral bone with increased BMD may lead to development of OA.¹⁶ However, elevated BMD levels at sites remote from the arthritic process cannot be explained by local biomechanical factors, and the question of whether primary OA rather is a systemic bone disease has been raised.¹⁷ Systemic changes in subchondral bone could be explained by genetic factors, hormonal influences, vitamin D concentrations, growth factors or activity of bone‐forming cells.^{15,18,19,20,21} Better knowledge about the relationship between BMD and HOA may contribute to the understanding of the pathogenesis of OA.Disease registers of patients with RA²² and HOA²³ have been established in the city of Oslo. We have previously compared BMD levels in a cohort of RA patients from the Oslo RA Register (ORAR) and healthy controls.²⁴ The current study was designed to compare levels of BMD and the frequency of osteoporosis between patients with HOA, RA and controls. A second aim was to explore possible relationships between BMD levels and disease characteristics in patients with HOA.