Anatomical reconstruction of the anterior cruciate ligament in goats

A surgical procedure was developed for the implantation of an anatomical, two-banded anterior cruciate ligament (ACL) prosthesis. Prostheses were fabricated of braided long-chain polyethylene fibers. The left ACL of adult male goats was surgically excised and replaced with either an anatomical reconstruction (5 goats) or a conventional reconstruction (5 goats). The anatomical reconstruction required drilling four bone tunnels, two each in the femur and tibia. Each band of the prosthesis was placed through one tunnel in the femur and the corresponding tunnel in the tibia, recreating the anteromedial and posterolateral bands. The two bands were tensioned independently and stapled in place. In the conventional procedure, the prosthesis was doubled and placed through two larger tunnels, one in the femur and one in the tibia, tensioned and stapled together. All animals were terminated 3 months after surgery. Clinical evaluation of passive range of motion, antero-posterior laxity and the appearance of the joint space showed little or no difference between the reconstruction methods. The ultimate failure load for the natural (unoperated) ACL was 1691 +/- 210 N, while the anatomical and conventional reconstruction groups had mean ultimate failure loads of 1233 +/- 732 and 1012 +/- 220 N, respectively. The elongation to failure of all groups was similar: the natural ACL group = 7.1 +/- 2.8 mm, the anatomical group = 7.2 +/- 2.9 mm, and the conventional group = 7.7 +/- 3.9 mm. The slope of the load-deformation curve, or stiffness, was significantly higher for the natural ACL (4.53 +/- 1.24 x 10(5) N/m) than for either of the reconstruction methods (2.75 +/- 1.59 x 10(5) N/m for the anatomical and 2.34 +/- 0.60 x 10(5) N/m for the conventional). The energy to failure, or area under the load-deformation curve, showed no significant difference between groups. In conclusion, both types of reconstructions were less strong, stiff, and tough than the natural ACL. There was no significant difference observed between the anatomical and conventional reconstruction methods over the 3-month implantation time in either clinical evaluation or mechanical testing. Therefore, at 3 months postsurgery, the anatomical reconstruction technique was considered no better and no worse than the conventional reconstruction technique.