Changes in subchondral bone structure and mechanical properties do not substantially affect cartilage mechanical...

Area of Science:

• Biomechanics
• Biomaterials Science
• Orthopedics

Background:

• Subchondral bone structural changes are characteristic of osteoarthritis (OA).
• The mechanical consequences of early-stage OA-related subchondral bone alterations on the osteochondral unit remain poorly understood.
• Understanding these effects is crucial for developing effective OA treatments.

Purpose of the Study:

• To investigate the influence of subchondral bone structure and mechanical properties on osteochondral unit mechanics.
• To quantify the impact of varying trabecular bone volume fraction, subchondral bone plate thickness, and equilibrium modulus on stress and strain distribution.
• To assess how experimentally observed early OA changes in subchondral bone affect cartilage mechanics.

Main Methods:

• Construction of a 3-D finite element model of a rabbit femoral condyle using micro-CT data.
• Application of creep loading in an indentation simulation.
• Systematic variation of trabecular bone volume fraction, subchondral bone plate thickness, and equilibrium modulus to mimic early OA conditions.

Main Results:

• Reduced trabecular bone volume fraction (48% to 28%) decreased maximum principal strain at the cartilage-bone interface by 50%.
• A 100 μm reduction in subchondral bone plate thickness decreased maximum principal stress at the interface by 36%.
• Changes in subchondral bone parameters had minimal impact on overall cartilage mechanics, except with an unrealistically soft bone plate.

Conclusions:

• Experimentally observed early OA subchondral bone changes exert minimal influence on cartilage mechanics during creep indentation.
• Significant alterations in cartilage mechanics were only observed under simulated conditions with an unrealistically soft subchondral bone plate.
• These findings highlight the resilience of cartilage mechanics to early subchondral bone structural modifications in osteoarthritis.