Mechanical Assessment of Human Articular Cartilage Issued from Asymptomatic & Total Knee Replacement Donors

Introduction: The objective of this study was to show the potential of a novel automated indentation and thickness technique to characterize mechanical properties and thickness distribution across entire articular surfaces providing a new assessment and diagnostic parameter (DP) that allows the classification of cartilage in three ranges: ‘normal’, ‘degenerated’ and ‘abnormally thin and degenerated’.

Materials and Methods: Two age-matched groups of 8 asymptomatic (where the average was considered as the reference once the degraded regions are removed) and 2 human tibial plateaus (TP) from total knee replacement (TKR) were mapped ex vivo using the Mach-1 mechanical tester (v500css, Biomomentum Inc.) in order to assess the instantaneous modulus (IM) and thickness through an automated indentation and thickness technique. Samples from each group were compared to the reference and a diagnostic parameter (DP) was calculated as the difference between the measured parameter and the reference parameter at the same location for IM and thickness.

Results: Mapping of IM and thickness revealed significant spatial variation between asymptomatic and TKR samples. Based on the diagnostic parameter (DP), different stages of degeneration were defined (Fig.1). From asymptomatic to TKR samples, the DP of IM revealed a transition from normally to degenerated and then to abnormally thin/degenerated cartilage. As for the thickness, the cartilage first became thicker but then thinner at later-stage in the TKR cartilage.

Conclusions: The potential of mechanical assessment of asymptomatic and TKR cartilage in human samples was highlighted and validated with the thickness measurements. The DP revealed an ability to distinguish between the different stages of degeneration.

Acknowledgements: The authors acknowledge the TKR samples donors for their participation, RTI Surgical for providing cadaveric asymptomatic articular surfaces, Biomomentum Inc. and MÉDITIS program for their funding and contribution to the successful completion of this research.