Independent Suture Tape Internal Brace Reinforcement of Bone-Patellar Tendon-Bone Allografts: Biomechanical Assessment in a Full-ACL Reconstruction Laboratory Model.

Abstract

Internal bracing for anterior cruciate ligament (ACL) surgery is a relatively new concept. The purpose of this study was to evaluate the effects of an "independent" button-fixed internal brace on the biomechanical properties of ACL reconstruction in a full-construct experimental model. Three groups (<i>n</i> = 10 each) were tested in a full-construct porcine-bone model with human bone-patellar tendon-bone allografts using different reconstruction techniques: interference screw fixation on femur and tibia (S-S group), adjustable-loop device (ALD) fixation on the femur with tibial interference screw without suture tape (ALD-S group), and with internal brace (ALD-S-IB group). Measured outcomes included cyclic displacement, stiffness, and ultimate load to failure. The ALD-S-IB group (2.9 ± 0.8 mm) displaced significantly less than the ALD-S (4.2 ± 0.9 mm; <i>p</i> = 0.015) and S-S group (4.3 ± 1.1 mm; <i>p</i> = 0.017). No significant difference was found between the ALD-S and the S-S group. Construct stiffness was significantly higher for the ALD-S-IB group (156 ± 23 N/mm) and the ALD-S group (122 ± 28 N/mm) than for the S-S group (104 ± 40 N/mm; <i>p</i> = 0.003 and <i>p</i> = 0.0042), but there was no significant difference between both ALD groups. Similarly, ultimate loads in the ALD-S-IB (758 ± 128 N) and the ALD-S groups (628 ± 223 N) were significantly greater than in the S-S group (416 ± 167 N; <i>p</i> < 0.001 and <i>p</i> = 0.025), but there was no significant difference between ALD groups. Adding an internal brace reinforcement to an ALD in a full-construct experimental model significantly decreased cyclic displacement by 31% without increasing construct stiffness or ultimate load significantly. These results indicate that suture tape internal bracing of bone-patellar tendon-bone allograft ACL reconstruction decreases cyclic displacement during experimental testing, which has clinical implications regarding initial construct stability.