Flat-Tunnel Technique With Independently Tensioned Bundles Better Restores Rotational Stability Than Round-Tunnel Technique in Anatomic Anterior Cruciate Ligament Reconstruction Using Hamstring Graft: A Cadaveric Biomechanical Study

Purpose: To investigate the kinematics differences between round-tunnel (ROT) and flat-tunnel (FLT) techniques in anterior cruciate ligament (ACL) reconstruction when using hamstring graft. Methods: Nine matched pairs of fresh-f rozen cadaveric knees were evaluated for the kinematics of intact, ACL-sectioned, and either ROT or FLT reconstructed knees. The graft bundles for FLT technique were separately tensioned. A 6 degrees of freedom robotic system was used to assess knee laxity: (1) 134-N anterior tibial load at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion; ( 2) 10 Nm of valgus torque followed by 5 Nm of internal rotation torque simulates a pivot-shift test at 15 degrees and 30 degrees; (3) 5-Nm internal and external rotation torques at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees; (4) 10-Nm varus and valgus torques at 15 degrees and 30 degrees. Results: Significant differences were found for ROT versus FLT techniques in terms of the simulated pivot-shift test at 15 degrees (2.5 mm vs 1.4 mm, respectively, difference from intact; P = .039) and the internal rotation test at 15 degrees (2.5 degrees vs 0.5 degrees, respectively, difference from intact; P = .034) and 30 degrees (2.0 degrees vs 0.4 degrees, respectively, difference from intact; P = .014). No significant differences were found between groups during 134-N anterior tibial load, external rotation and valgus/varus rotation. Neither technique was able to reproduce the intact state during an anterior tibial load and simulated pivot-shift test. Conclusions: The FLT technique with independently tensioned bundles shows the same anterior control as the ROT technique but better restores rotational stability in terms of the simulated pivot-shift test and the internal rotation test in anatomic ACL reconstruction at time zero.

Automated summary

This study compared the kinematics differences between round-tunnel and flat-tunnel techniques in anterior cruciate ligament (ACL) reconstruction using hamstring grafts. The results showed that the flat-tunnel technique provided better rotational stability but couldn't fully restore the intact state of the knee.