Cartilage is a dense connective tissue of the musculoskeletal system with complex biomechanical response to imparted loads. The objective of this project was to explore how cartilage mechanics relates to tissue integrity during long-term storage.

Chapter 1 provides a literature summary of articular cartilage, including its composition and electrochemical properties. Prevailing cartilage mechanics theories are discussed including the biphasic and polymer dynamics theories.

Chapter 2 examined the effects of the supplement DADLE on stored cartilage specimens. DADLE is a delta opioid receptor agonist. Opioid-like chemicals, such as DADLE, have been shown to induce a hibernation-like state when injected into hibernating animals during nonhibernating seasons. The data suggest DADLE-supplemented storage media could slow the metabolic activity of stored chondrocytes, extending their viability beyond current limits. The first experiment investigated the effects of DADLE on cartilage stored in two environments. Subsequently, the dose response effects of DADLE were examined on specimens stored in an incubator environment. We hypothesized that DADLE would act as a protective agent as measured through mechanical and biological tests. DADLE appeared to provide protection during storage in the Environment and Media experiment, but the results were not confirmed in the Dose Response experiment. The results for DADLE as a storage media supplement suggest it is not effective at protecting the tissue in storage and need to be further explored with larger sample sizes and additional assays.

Chapter 3 explored fluid pressurization in cartilage. Under compression, cartilage interstitial fluid is pressurized. This fluid pressurization provides some of the load-carrying ability of cartilage. Previous studies explained that the fluid pressurization caused flow of interstitial fluid through the tissue eventually leading to tissue relaxation. This experiment examined fluid pressurization and flow-independent mechanisms of cartilage relaxation. A specially-designed fixture was used to test bovine calf cartilage in unconfined compression while monitoring fluid pressurization. Although it is not completely clear why, our experiments were inconsistent with results in the literature. With no discernable leaks, our experiments did not observe a decay of fluid pressure to zero at stress equilibrium. These results are inconsistent with fluid flow as a significant mechanism of fluid pressurization modulation. This is a noteworthy observation in contrast to previously published reports.