Monday  |  Lakeshore B  |  10:40 AM–11:20 AM

#19401, Keynote: Cartilage Fracture and Fatigue

Articular cartilage is a fibril-reinforced biocomposite that exhibits remarkable material properties including a low coefficient of friction, high resilience to large deformations, and broadband energy dissipation. While impressively evolved to provide a low-friction, pain-stimulus-free bearing surface for decades, cartilage can fail following mechanical overloading. Cartilage failure mechanisms and thresholds are poorly understood, in part because of its complex structure and behavior. The objective of this research is to identify mechanisms of cartilage failure under single and repeated loads, and to relate that failure to cartilage structure and sub-failure mechanics. Long-term, the objective is to translate these findings to applications in human health.

We developed an experimental model using microfracture to induce failure under single loads, then extended this model to evaluate the effect of cyclic uniaxial compression after microcracking. Results demonstrated that cartilage poroviscoelastic energy dissipation drives the timing of cartilage failure, and that failure is therefore coupled to both glycosaminoglycan content and to solvent osmolarity. Failure under fast loading enables estimates of cartilage toughness. Across loading rates, both clustering of experimental data and finite element modeling suggest that cartilage failures is ductile under slow loading and brittle under fast loading. While these data were primarily collected using porcine cartilage, key features translate to human cartilage. In addition, preliminary data on human cartilage demonstrate regional variation in failures, which helps to interpret trends in disease initiation and progression. When extended to failure under cyclic loading, experimental results showed crack extension and bulk softening that was dependent on frequency and load level.

Corinne Henak   University of Wisconsin-Madison