A nanoindentation technique for functional evaluation of cartilage repair tissue

Cartilage repair is an ongoing challenge in orthopaedic research. Both biological and mechanical properties are needed for full functional characterization of a tissue replacement. However, assessment of cartilage repair tissue has relied primarily on histological markers because mechanical properties are difficult to measure in small tissue regions. Nanoindentation is a technique that is specialized for measuring local mechanical properties in small specimens. In this study, nanoindentation was used to measure the mechanical properties of cartilage repair tissue following microfracture treatment of chondral defects in three rabbit knees. The mechanical properties were then correlated with histology findings from the same tissue samples. Nanoindentation provided complementary information to histology. In particular, the nanoindentation results showed that the mechanical properties of the repair tissue were inferior to the control tissue properties, even though some tissue regions were histologically similar to the control tissue.