Abstract
Osteoarthritis is the most common musculoskeletal disabling disease worldwide. Preclinical studies on mice are commonly performed to test new interventions. Finite element (FE) models can be used to study joint mechanics, but usually simplified geometries are used. The aim of this project was to create a realistic subject specific FE model of the mouse knee joint for the assessment of joint mechanical properties. Four different FE models of a C57Bl/6 female mouse knee joint were created based on micro-computed tomography images of specimens stained with phosphotungstic acid in order to include different features: individual cartilage layers with meniscus, individual cartilage layers without meniscus, homogeneous cartilage layers with two different thickness values, and homogeneous cartilage with same thickness for both condyles. They were all analyzed under compressive displacement and the cartilage contact pressure was compared at 0.3 N reaction force. Peak contact pressure in the femur cartilage was 25% lower in the model with subject specific cartilage compared to the simpler model with homogeneous cartilage. A much more homogeneous pressure distribution across the joint was observed in the model with meniscus, with cartilage peak pressure 5–34% lower in the two condyles compared to that with individual cartilage layers. In conclusion, modeling the meniscus and individual cartilage was found to affect the pressure distribution in the mouse knee joint under compressive load and should be included in realistic models for assessing the effect of interventions preclinically.
Highlights
Osteoarthritis (OA) is highly prevalent in our aging society (Wallace et al, 2017) and is the most common degenerative joint disorder, affecting 8.5 million adults in the UK (Neogi, 2014) and costing the economy more than 4.2 billion pounds (Chen et al, 2012)
The highest average and peak contact pressure in the lateral femoral cartilage was found for the model with one layer of generalized cartilage, followed by the model with two layers of cartilage with different thickness values, by the model with individual cartilage, and by the model with individual cartilage and meniscus
The highest average and peak contact pressure in the medial femoral cartilage was found for the model with two thickness layers of generalized cartilage, followed by the model with individual cartilage, and by the model with individual cartilage and meniscus
Summary
Osteoarthritis (OA) is highly prevalent in our aging society (Wallace et al, 2017) and is the most common degenerative joint disorder, affecting 8.5 million adults in the UK (Neogi, 2014) and costing the economy more than 4.2 billion pounds (Chen et al, 2012). Realistic finite element (FE) models of the whole mouse joint would be helpful to study the effect of interventions and treatments on the mechanical properties of the cartilage (Silva et al, 2005; Das Neves Borges et al, 2014; Yang et al, 2014). A recent study showed that high-resolution systems and phase contrast can be used to visualize the cartilage geometry of osteochondral plugs without staining (Clark et al, 2019) This approach has not been validated on whole joints of rodents yet. The FE models did not include the menisci, which was found to play a critical role in the joint mechanics (Ramos-Mucci et al, 2020)
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