Biomechanical Comparison of Single-Tunnel—Double-Bundle and Single-Bundle Anterior Cruciate Ligament Reconstructions

BACKGROUND: Anatomic double-bundle reconstruction has been thought to better simulate the anterior cruciate ligament anatomy. It is, however, a technically challenging procedure, associated with longer operation time and higher cost. HYPOTHESIS: Double-bundle anterior cruciate ligament reconstruction using a single femoral and tibial tunnel can closely reproduce intact knee kinematics. STUDY DESIGN: Controlled laboratory study. METHODS: Eight fresh-frozen human cadaveric knee specimens were tested using a robotic testing system to investigate the kinematic response of the knee joint under an anterior tibial load (130 N), simulated quadriceps load (400 N), and combined torques (5 N.m valgus and 5 N.m internal tibial torques) at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. Each knee was tested sequentially under 4 conditions: (1) anterior cruciate ligament intact, (2) anterior cruciate ligament deficient, (3) single-bundle anterior cruciate ligament reconstruction using quadrupled hamstring tendon, and (4) single-tunnel-double-bundle anterior cruciate ligament reconstruction using the same tunnels and quadrupled hamstring tendon graft as in the single-bundle anterior cruciate ligament reconstruction. RESULTS: Single-tunnel-double-bundle anterior cruciate ligament reconstruction more closely restored the intact knee kinematics than single-bundle anterior cruciate ligament reconstruction at low flexion angles (< or =30 degrees ) under the anterior tibial load and simulated muscle load (P < .05). However, single-tunnel-double-bundle anterior cruciate ligament reconstruction overconstrained the knee joint at high flexion angles (> or =60 degrees ) under the anterior tibial load and at 0 degrees and 30 degrees of flexion under combined torques. CONCLUSION: This double-bundle anterior cruciate ligament reconstruction using a single tunnel can better restore anterior tibial translations to the intact level compared with single-bundle anterior cruciate ligament reconstruction at low flexion angles, but it overconstrained the knee joint at high flexion angles. CLINICAL RELEVANCE: This technique could be an alternative for both single-bundle and double-tunnel-double-bundle anterior cruciate ligament reconstructions to reproduce intact knee kinematics and native anterior cruciate ligament anatomy.