|Title:||Development of a technique and protocol for the study of depth-dependent compressive property of bovine articular cartilage|
Hong Kong Polytechnic University -- Dissertations
Jockey Club Rehabilitation Engineering Centre
|Pages:||xiii, 97 leaves : ill. ; 30 cm|
|Abstract:||Articular cartilage covers the ends of all movable joints (66). Its main function includes providing joints with excellent lubrication required for frequent gliding motion (66). Inside cartilage, there are living cells known as chondrocytes. They secrete extracellular matrices which govern the biomechanical properties of articular cartilage (24,37,43). The primary compositions of the extracellular matrices are proteoglycans, collagens and water. Microscopically, the compositions and structural organization along the depths of cartilage vary (37,43,66). Besides, they also vary throughout the lifetime, depending on the pathological state, age and history of loading (10-12,43). In previous studies (1,2,5-7,15,20,24-27,36,37,39,41-43,45,48,53,61), it was found that the biomechanical properties of articular cartilage were related to the compositions, concentration, and structural organization of solid matrices. However, how exactly these factors contribute to the biomechanical properties of articular cartilage are still areas for active research. Results of biomechanical assays in the forms of indentation test, confined and unconfined compression, shear test and tensile test were used to correlate with the results of the biochemical assays. Now, with the fast-growing quantitative image analysis, semi-quantification of the solidity of the tissue histology was possible (22,52,57,58,65). Besides, to our knowledge, these biomechanical tests were mainly done on full-thickness cartilage. Researches on dissected cartilage were relatively rare. Only tensile tests on dissected cartilage were documented (1,43,51,60). No compressive test on dissected cartilage was documented. In this study, nine bovine tibial plateaus were divided into three equal portions. They were treated with 1mg/ml Trypsin solution for zero, one and four hours. This treatment was used to simulate the situation of osteoarthritis (8). Six around 11mm diameter cartilage-bone plugs from each portion were harvested. The full-thickness cartilage-bone plugs were cut into two sides. From one side, the full-thickness cartilage was carefully microtomed into three slices from different depths. These slices were then cored with an approximately 6mm diameter drill. Finally, three cartilage disks from each cartilage-bone plug were obtained. They were then tested in unconfined compression. The other side full-thickness cartilage was stained with 0.1% Safranin O and counterstained with 0.1% fast green for histological analysis. The stained cartilage was examined under an image analyser Leica Q500MC, which was used to quantitatively measure the relative grey intensity. The relative grey intensity was then normalized for comparative purposes. Results of the image analysis and those of the biomechanical test were studied to obtain a relationship between the normalized grey intensity and the normalized biomechanical property. The applications for the technique and protocol developed in this study are quite broad. For example, it can be further developed as a biopsy diagnostic tool for detection of early osteoarthritis. It was documented (16) that for an osteoarthritic joint, the solidity of the involved cartilage was much lower than that of a healthy joint. Depending the extent of the degeneration, different depths of the tissue can be involved, starting from the articular surface. With suitable color stain, the inhomogeneous color intensity from the captured image along the depths of the cartilage may reveal the status of the disease.|
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