Biomechanical and Histological Effects of Different Regimens of Immobilzation after Operative Treatment in a Ruptured Rabbit Achilles Tendon

Kim, Kyung Cheon; Hwang, Deuk Soo; Chung, Sang Yun; Woo, Se Min; Lee, Choong Hui

Abstract

PURPOSE
To evaluate the effects of the different regimens of immobilization after surgery in a rabbit model. MATERIALS AND METHODS: The study was performed on the right Achilles tendon of 30 rabbits. Modified Kessler method was used to suture the transected tendon. Rabbits were divided into three groups, Group I (n=10) underwent long leg cast with equinus position for 6 weeks, Group II (n=10) underwent weekly cast correction to full dorsiflexion from 1 week after surgery, and Group III (n=10) underwent daily correction of equinous position with external fixator from 1 week after surgery. The contralateral Achilles tendon served as an unoperated control. And three groups were compared at 6 weeks after surgery. RESULTS: The maximal load at rupture (N) was 55.50, 97.46, 140.27, 180.98 for group I, II, III and control respectively. The strain was 0.44, 0.49, 0.74, 0.67. The stiffness (N/mm) was 9.63, 17.87, 19.01, 23.33. The absorbed energy to rupture (J) was 12.23, 23.98, 51.20, 60.78. Values among groups were significantly different considering the maximal load, strain, stiffness, and absorbed energy to rupture (p<0.05). Histological finding was revealed more mature restoration and more parallel arrangement of fiber bundles in the group II, and especially group III. Achilles tendon rupture, Maximal load, Strain, Stiffness, Tensile loading. CONCLUSION: Tensile loading of the healing tendon by postoperative continuous correction leads to changes in more similar to the normal Achilles tendon, biomechanically and historically.