Influence of the Different Types of Tibial Fixation in the Reconstruction of the Anterior Cruciate Ligament of the Knee: Osseous Integration, Ligament Maturation and Clinical Results.

Influence of different tibial fixation methods in anterior cruciate ligament (ACL) reconstruction: bone integration, graft maturation, and clinical outcomes. Primary Objective To assess whether any of the three tibial fixation techniques is superior in terms of: * Graft-bone integration (CT/MRI). * Graft maturation (MRI, signal-to-noise quotient at 12 months). * Clinical outcomes (IKDC, Lysholm and Tegner scores; manual and instrumented knee stability with the Lachman and pivot-shift tests and the KT-1000 arthrometer). Secondary Objectives * Compare clinical outcomes among groups (IKDC, Lysholm, Tegner). * Compare complication and re-rupture rates and patient satisfaction among groups. Study Design Prospective, single-center, three-arm randomized controlled trial. Inclusion Criteria * Age 18 to 50 years. * Primary complete ACL tear with indication for arthroscopic reconstruction with hamstring autograft. Exclusion Criteria * Revision ACL surgery. * Use of a graft other than hamstring tendons. * Kellgren-Lawrence grade III-IV osteoarthritis. * Inflammatory knee disease. Note: soft tissue procedures (e.g., meniscal repair) are not exclusion criteria. Randomization Patients meeting the inclusion and exclusion criteria are randomized (Research Randomizer, https://www.randomizer.org/) into 3 groups: * Group A (TORN): bioabsorbable interference screw, same diameter as the tunnel. * Group B (TORN+1): bioabsorbable interference screw, 1 mm larger than the tunnel diameter. * Group C (TORN-BT): interference screw (same diameter as the tunnel) plus second fixation with a cortical button. Sample size: 37 patients per group, 111 in total. Follow-up * Preoperative radiographic evaluation. * CT at 15 days and at 12 months postoperatively. * MRI at 12 months postoperatively. * Clinical follow-up at 2 years postoperatively. Statistical Analysis Pre- and postoperative variables will be compared within groups, and all variables will be compared between groups using parametric or non-parametric tests according to data distribution (Student's t-test or ANOVA, or their non-parametric equivalents). Linear regression models will be applied to test for potential significance that could be masked by confounding factors.

Inclusion Criteria * Age 18 to 50 years. * Primary complete ACL tear with indication for arthroscopic reconstruction with hamstring autograft. Exclusion Criteria * Revision ACL surgery. * Use of a graft other than hamstring tendons. * Kellgren-Lawrence grade III-IV osteoarthritis. * Inflammatory knee disease. Note: soft tissue procedures (e.g., meniscal repair) are not exclusion criteria.