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Measuring microscale strain fields in articular cartilage during rapid impact reveals thresholds for chondrocyte death and a protective role for the superficial layer

Cornell Affiliated Author(s)

Author

L.R. Bartell
L.A. Fortier
L.J. Bonassar
Itai Cohen

Abstract

Articular cartilage is a heterogeneous soft tissue that dissipates and distributes loads in mammalian joints. Though robust, cartilage is susceptible to damage from loading at high rates or magnitudes. Such injurious loads have been implicated in degenerative changes, including chronic osteoarthritis (OA), which remains a leading cause of disability in developed nations. Despite decades of research, mechanisms of OA initiation after trauma remain poorly understood. Indeed, although bulk cartilage mechanics are measurable during impact, current techniques cannot access microscale mechanics at those rapid time scales. We aimed to address this knowledge gap by imaging the microscale mechanics and corresponding acute biological changes of cartilage in response to rapid loading. In this study, we utilized fast-camera and confocal microscopy to achieve roughly 85 μm spatial resolution of both the cartilage deformation during a rapid ( 3 ms), localized impact and the chondrocyte death following impact. Our results showed that, at these high rates, strain and chondrocyte death were highly correlated (p < 0.001) with a threshold of 8% microscale strain norm before any cell death occurred. Additionally, chondrocyte death had developed by two hours after impact, suggesting a time frame for clinical therapeutics. Moreover, when the superficial layer was removed, strain - and subsequently chondrocyte death - penetrated deeper into the samples (p < 0.001), suggesting a protective role for the superficial layer of articular cartilage. Combined, these results provide insight regarding the detailed biomechanics that drive early chondrocyte damage after trauma and emphasize the importance of understanding cartilage and its mechanics on the microscale. © 2015 Elsevier Ltd.

Date Published

Journal

Journal of Biomechanics

Volume

48

Issue

12

Number of Pages

3440-3446,

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942828572&doi=10.1016%2fj.jbiomech.2015.05.035&partnerID=40&md5=334411d3583c08339c4a202c80fe7e4a

DOI

10.1016/j.jbiomech.2015.05.035

Research Area

Group (Lab)

Itai Cohen Group

Funding Source

DMR-1056662
R21AR062677

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