Effects of postoperative immobilization on the reconstructed anterior cruciate ligament: An experimental study in rabbits

Abstract

To investigate the effects of postoperative immobiliza tion and limited motion on reconstructed anterior cru ciate ligaments, 28 rabbits received an anterior cruciate ligament reconstruction using autogenous Achilles ten don and were then divided into three groups: Fully immobilized, 4 weeks immobilized, and limited motion. Two rabbits from each group were evaluated macro scopically, histologically, and microangiographically at 4-week intervals until 12 weeks postoperatively. An additional six rabbits in the 4 weeks immobilized and limited motion groups were studied biomechanically at 12 weeks postoperatively. Macroscopically, both immobilized groups showed more proliferation of the infrapatellar fat pad, which was adherent to the reconstructed anterior cruciate liga ment. Histology revealed more rapid regeneration of reconstructed anterior cruciate ligaments in the limited motion group, with no findings of necrosis in the mid- substance. Microangiography indicated faster normali zation of vascularity in the limited motion group. The biomechanical study showed no significant difference in laxity between the 4 weeks immobilized and limited motion groups. The graft stiffness and maximum load to failure were greater for the limited motion group, although the increase was not statistically significant. The histologic and microangiographic results from the limited number of animals in this study support limited postoperative motion in the anterior cruciate ligament reconstructed knee. However, there were no differ ences in terms of the biomechanical parameters at 12 weeks postoperatively between the immobilized and limited motion treatment modes. © 1993, SAGE Publications. All rights reserved.