Biomechanical Study of the Pull-Out Strength of Interference Screw Fixation in Anterior Cruciate Ligament Reconstruction: Comparison Between Endoscopic and Arthroscopic Assisted Technique

Rah, Soo Kyoon; Choi, Chang Uk; Lee, Byung Il; Shin, Byung Joon; Ha, Sang Sun

Abstract

Surgical reconstruction of the anterior cruciate ligament is undergoing constant evolution. The variable success of these procedures can be attributed to many factors including graft selection, graft placement, graft tensioning, graft remodelling and rehabilitation program. Rigid fixation is probably the most important factor in the success of these procedures during the initial stages of healing. Arthroscopically assisted reconstruction of the ACL-deficient knee using a bone-patellar tendon-bone graft(two-incision technique) is a reliable and evolving technique. Rosenberg et al, described a one-incision technique that allows endosteal fixation of bone plugs within their femoral tunnels intraarticularly via the intercondylar notch. These two techniques are different from their femoral tunnel direction and bone plug placement. The present study was designed to develop a swine model for in vitro biomechanical testing of the bone-patellar tendon-bone ACL autograft to compare the pull-out strength of Outside-In technique and Inside-Out technique. The result were as follows: 1. Normal ACL(N=10 knees) pull-out tensile strength tests showed a maximum tensile strength of 1295.34(N), a stiffness of 120.95(N/mm), and a linear load of 1104.26(N). The failure sites were all tibial attachments. 2. Femoral and Tibial interference fit pull-out tensile strength tests(N=10 knees) showed a maximum tensile strength of 463.23±42.27(N), a stiffness of 33.62±3.18(N/mm), and a linear load of 392.51±95.42(N). The failure sites were all in the tibial tunnel area(N=9 knees), except for one which femoral tunnel area. 3. Inside-Out technique(N=15 knees) showed a maximum tensile strength of 1250.64±75.67(N), a stiffness of 94.31±26.44(N/mm), and a linear load of 1046.92±367.55(N), but the Outside-In tech-nique(N=15 knees) showed a maximum tensile strength of 805.35±54.61(N), a stiffness of 83.33±10.98(N/mm), and a linear load of 685.99±86.32(N)(p < 0.0001). The failure sites were all in the femoral tunnel area. 4. Tensile testing demonstrated that the Inside-Out technique was significantlly stronger than Outside-In technique for maximum tensile strength, stiffness and a linear load.