C. F. Zhu

The objective of this review is to provide basic information pertaining to biomechanical aspects of bone as they relate to tissue engineering. The review is written for the general tissue engineering reader, who may not have a biomechanical engineering background. To this end, biomechanical characteristics and properties of normal and repair cortical and cancellous bone are presented. Also, this chapter intends to describe basic structure-function relationships of these two types of bone. Special emphasis is placed on salient classical and modern testing methods, with both material and structural properties described.

Dorsal carpal osteochondral injury is a major cause of reduced performance in horses undergoing high-intensity training. It was hypothesised that the mechanical behaviour and histology of cartilage are influenced by the intensity of exercise and by location within a joint. Relationships between histology and mechanical behaviour were identified in 2-year-old horses undergoing 19 weeks of high-intensity treadmill training or low-intensity exercise and then compared between groups. Dorsal and palmar test sites were identified on radial, intermediate, and third carpal articular surfaces after euthanasia. The mechanical properties of cartilage were determined with an automated creep indentation apparatus as previously described for equine cartilage. Cartilage morphology was assessed with use of sections stained with haematoxylin and eosin and toluidine blue. Dorsal cartilage was less permeable, thinner, and had a loss of chondrocyte alignment compared with palmar cartilage. Cartilage from strenuously trained horses showed more fibrillation and chondrocyte clusters than did cartilage from gently exercised animals. Dorsal radial carpal cartilage and third carpal cartilage of strenuously trained animals were significantly less stiff than that from gently exercised animals, and the former had reduced superficial toluidine blue staining compared with that from the gently exercised group. These results indicate that topographical and exercise-related differences exist in the morphology and mechanical properties of carpal cartilage and suggest that strenuous training may lead to deterioration of cartilage at sites with a high clinical incidence of lesions.

This study examined the relationship between acetabular cartilage properties after hemiarthroplasty surgery and surgical variables including femoral head size and position. Nineteen sheep received unilateral hip arthroplasties and were euthanized one year post-operatively to harvest the femora and acetabula. Cartilage histology, biochemistry and material properties were determined from samples located in the superior load-bearing region. Femoral head size mismatch, leg length difference, anterior-posterior and medial lateral offset and anteversion were measured. In the acetabulum. substantial cartilage degradation occurred with widespread librillation and significant changes in the biochemical and material properties compared to the intact contralateral joint. Regression analyses on the surgical variables explained 75-80% of the changes in tissue biochemistry but did not explain the material changes. Head size mismatch and leg length difference were the most significant contributors of the five variables examined and therefore may be critical to successful outcome in hemiarthroplasty.