Microscale strain mapping demonstrates the importance of interface slope in the mechanics of cartilage repair

Rebecca M Irwin; Tianyu Gao; Alexander J Boys; Kyla Ortved; Itai Cohen; Lawrence J Bonassar

doi:10.1016/j.jbiomech.2020.110159

Microscale strain mapping demonstrates the importance of interface slope in the mechanics of cartilage repair

J Biomech. 2021 Jan 4:114:110159. doi: 10.1016/j.jbiomech.2020.110159. Epub 2020 Dec 3.

Authors

Rebecca M Irwin¹, Tianyu Gao², Alexander J Boys², Kyla Ortved³, Itai Cohen⁴, Lawrence J Bonassar⁵

Affiliations

¹ Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States.
² Department of Materials Science and Engineering, Cornell University, Ithaca, NY, United States.
³ Comparative Orthopaedics Laboratory, Cornell University, Ithaca, NY, United States(1).
⁴ Department of Physics, Cornell University, Ithaca, NY, United States.
⁵ Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY, United States; Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, United States. Electronic address: lb244@cornell.edu.

Abstract

Achieving lateral integration of articular cartilage repair tissue with surrounding native cartilage remains a clinical challenge. Histological and bulk mechanical studies have identified extracellular matrix components that correlate with superior failure strength, but it is unclear how local changes in geometry and composition at the repair interface affect tissue strains under physiologic loading. Here, we investigated the effects of local compositional and interface geometry on lateral cartilage repair integration by coupling microscale Raman spectroscopy and confocal elastography to measure tissue strains under compressive and shear loading. Histological integration assessments did not have significant relationships with interface strains under compressive loading (p > 0.083) and only the perimeter attachment score was trending towards statistical significance with the |E_xy| strain tensor under shear loading (p = 0.050). Interface slope had a stronger correlation with local tissue strains under compressive and shear loading compared to compositional measures of GAG, collagen, or proteins (compressive loading |E_yy| tensor: R² = 0.400 (interface slope), 0.005 (GAG), 0.024 (collagen), and 0.012 (protein); shear loading |E_xy| tensor: R² = 0.457 (interface slope), 0.003 (GAG), 0.006 (collagen), and 0.000 (total protein)). These data support surgical publications detailing the need for vertical walls when debriding chondral defects. Current histological integration assessments and local compositional measures were insufficient for identifying the variation in interface strains under compressive and shear loading. Thus, our data points to the importance of controlling interface geometry at the time of surgery, which has implications for cartilage repair integration and long-term healing.

Keywords: Biomechanics; Collagen; Composition; Elastography; Glycosaminoglycans; Integration; Raman spectroscopy.

Publication types

Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Cartilage, Articular*
Chondrocytes
Collagen
Pressure

Substances

Collagen

Abstract

Publication types

MeSH terms

Substances

Grants and funding