Subchondral bone turnover, but not bone volume, is increased in early stage osteoarthritic lesions in the human hip joint

OBJECTIVE

The pathogenesis of osteoarthritis (OA) is not fully understood, but bone changes are suggested to be important. Bone turnover and bone volume (BV) in human hip OA were investigated in relation to the overlying cartilage degeneration using design-based stereological estimators.

MATERIALS AND METHODS

Femoral heads were obtained from 25 end-stage OA patients and 24 controls (CTL). Design-based stereological methods were used for sampling and quantification to obtain absolute estimates of volume and surface in the central trabecular and the subarticular bone region. The subarticular bone was further subdivided into regions according to the OARSI-score of the overlying articular cartilage in which erosion and osteoid surfaces were estimated.

RESULTS

In the subarticular region, bone volume (BV/TV) was 15.0% higher in OA patients compared to CTL; The fraction of erosive (ES/BS) and osteoid surfaces (OS/BS) were 56.2% and 72.8% higher in OA compared to CTL. In subarticular regions with none to mild cartilage degeneration (OARSI grade 0-2), ES/BS and OS/BS were 48.6% and 59.9% higher in OA compared to CTL, whereas BV/TV did not differ between OA and CTL.

CONCLUSION

In human end-stage hip OA, BV and bone turnover correlate with the degree of local cartilage degeneration. Subarticular bone sclerosis was only present in regions corresponding to end-stage OA. However, in regions with only none to mild cartilage degeneration the underlying bone had significantly higher turnover in OA patients compared to the control group, suggesting that high bone turnover may contribute to the early pathogenesis of OA.

Microstructural alterations of femoral head articular cartilage and subchondral bone in osteoarthritis and osteoporosis

OBJECTIVE

Explore whether osteoporosis (OP) in humans influences the morphological status of the articular cartilage and the subchondral bone. Explore the relationship between the macroscopic aspect of the articular surface and the rate of microscopic changes of both the cartilage and the subchondral bone in OP and osteoarthritis (OA).

METHODS

Femoral heads after total hip replacement were obtained from patients with OP or hip OA (OP, n = 56; OA, n = 12). Cartilage degeneration was assessed using the Mankin grading system whereas subchondral bone was evaluated using histomorphometry and Micro-computed Tomography (μCT) scanning system. Thickness of the cartilage layers and subchondral cortical bone (SCB) was measured.

RESULTS

Samples with higher total Mankin score have significantly reduced cartilage thickness. Mankin score differed between all OP specimens. In OP samples with lower Mankin scores the thickness of SCB shows a trend of an increase caused by increased levels of bone remodeling. In OP samples with higher Mankin scores we observed thinning of SCB. Structural indices of subchondral trabecular bone (STB) were significantly lower in OP than in OA samples.

CONCLUSION

Thinning of SCB, found in OP samples with higher Mankin scores could be related with the progression of the cartilage degeneration indicating an early-stage OA. Increased levels of bone remodeling and evidently changed morphology of subchondral bone found in OP samples with lower Mankin score indicated that bony bed level must have a role in the progression of the cartilage degeneration.