Effects of abrasion therapy on tears in the avascular region of sheep menisci

This study was designed to test the hypothesis that abrasion of the parameniscal synovium aids healing of a stable tear in the avascular region of the meniscus in a sheep model. In six sheep, a 5–7-mm longitudinal fullthickness tear was made in the avascular inner half of the anterior part of the lateral meniscus. The parameniscal synovium was abraded superiorly and inferiorly from the meniscus periphery to the lesion. Three animals in a control group received identical meniscal tears but no abrasion treatment. A harness prevented weight bearing and maintained the knee fully flexed after surgery. Twelve weeks after the operation, no healing was seen in any tears. Histologic examination revealed in both groups increased numbers of dividing chondrocytes on either side of the tear. In the test group, several layers of fibroblasts, which appeared in two menisci to derive from the upper meniscal surface, were seen covering both cut surfaces of the tear. It is concluded that the distance from the periphery to the defect is too far for abrasion therapy to stimulate sufficient cellular ingrowth to facilitate repair of tears in the avascular region of the meniscus.