The purpose of this study was to characterize the repair tissue that develops after removal of a portion of the patellar ligament for use as a graft. A six-millimeter-wide strip was obtained from the central portion of the patellar ligament with tibial and patellar bone plugs from one knee (stifle joint) of eight goats. The repair tissue that formed in the defect was characterized in terms of its structural, material, histological, and ultrastructural properties twenty-one months after the operation. The contralateral patellar ligament served as a control. Representative specimens were taken from the proximal, middle, and distal portions of the repair tissue and the control tissue for histological study and examination with transmission electron microscopy. The six-millimeter-long defect filled with repair tissue that increased the cross-sectional area by a mean of 42 per cent compared with the control values (p < 0.05). The maximum force to failure and the ultimate stress of the repair tissue were significantly decreased (by a mean of 51 and 65 per cent, respectively) compared with those of the controls (p < 0.001 for both). The stiffness also was reduced, by a mean of 27 per cent, but this was not significant (p > 0.05). Magnetic resonance imaging of the donor site showed slightly increased signal intensity compared with the intensity on the control side. Histological sections from the donor site contained collagenous (scar) tissue that was less organized, more cellular, and more vascular than the control tissue. Evaluation of the ultrastructure revealed that the repair tissue was composed primarily of collagen fibrils with a small diameter (range, fifty to 100 nanometers). CLINICAL RELEVANCE: The results of the present study suggest that the repair tissue that develops after removal of a strip of the patellar ligament for use as a graft is not comparable with normal tissue in terms of its structural, material, histological, and ultrastructural properties by twenty-one months. This should be kept in mind when this repair tissue is considered for use as a graft for revision of a reconstruction of the anterior cruciate ligament.
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