[Effect of cyclic loads on revascularization in healing of bone defect]

In order to study the biomechanical effect of cyclic loads on revascularization in bone healing, 20 rabbits were chosen for following experiments. Two 2 mm in diameter holes were made at the middle segment of both right and left tibia. A 2 mm in diameter nail was put in 15 mm proximal to the upper hole, and another was put in 15 mm distal to the lower hole. The wound was covered by direct suture with the ends of the nails kept 15 mm out of skin. The medial ends of the two nails were fixed by an iron plate, while the lateral ends were left for cyclic loads. Three Hz cyclic loads, which was near to the cyclic forces when a rabbit runs, was added to the left tibia for experiment, and no loads was add to the right tibia for control. A group of five rabbits were sacrificed respectively in 5, 10, 20 and 30 days postoperatively. The solution of 2% India ink and gelatin was irrigated from aorta to the bone defects. Then the tibia was removed for histologic study. The changes of cells and microvessel were observed. It was shown that the revascularization in experiment group was about 7 days earlier than that of control. The effect was at its peak from 10 to 30 days. It was concluded that cyclic loads could promote revascularization in the healing process of bone defect.