No Differences in Objective Knee Laxity Measurements or Patient Reported Outcome Measures Between Fixed and Adjustable Loop Suspensory Fixation in Anterior Cruciate Ligament Reconstruction: 1-Year Results from the GAP Study, A Prospective, Double-Blinded, Randomized Trial.

Introduction: Suspensory fixation is one of the most common graft fixation methods in anterior cruciate ligament (ACL) reconstruction and can be performed with either a fixed-loop device or adjustable-loop device. There has, however, been a paucity of comparative clinical data and a clear need for an adequately powered, double-blinded, randomized study. to determine whether there is any difference in objective knee laxity between these fixation methods. The GAP study was designed to address this need.

Methods: In a single-centre, two-surgeon series, 164 patients were recruited and randomized to receive a hamstring autograft ACL reconstruction using either a fixed-loop or adjustable-loop femoral fixation (Stryker G-Lock or ProCinch, respectively). Patients and assessors were blinded. Knee laxity was the primary outcome measure and measurements were taken using the GNRB (Genourob, Laval, France) knee arthrometer set at 150N and 200N respectively. Measurements were taken from the operated leg and compared to the contralateral leg. Patient reported outcome measures (PROMs) were collected at baseline, 6 months and 12 months and a linear regression analysis was undertaken.

Results: At 1-year, 121 patients (62% male; mean age 31, SD 9.8) had complete knee laxity assessments. Of these, 58 received the fixed-loop fixation and 63 the adjustable-loop device. At 150N, the operated-knee laxity in the fixed-loop group was 5.51mm (SD 1.40; 95% CI 5.14-5.87) versus 5.61mm (SD 1.39; 95% CI 5.26-5.96) in the adjustable-loop group (P=0.68). At 200N, the operated-knee laxity in the fixed-loop group was 6.94mm (SD 1.54; 95% CI 6.53-7.34) versus 7.02mm (SD 1.53; 95% CI 6.63-7.40) in the adjustable-loop group (P=0.77). There was no statistically significant difference in the between-knee laxity measurements or PROMs (Tegner Activity Score, International Knee Documentation Committee [IKDC] Subjective Knee Evaluation Form, Lysholm Score, or any of the Knee injury and Osteoarthritis Outcome Score [KOOS] domains) between the groups.

Conclusion: The GAP study is the first to compare knee laxity measurements between these two graft fixation devices in a randomized and blinded study. No statistically significant differences were observed in absolute or relative (operated vs. non-operated) knee laxity measurements or PROMs. These important new findings should inform surgeons and patients when considering graft fixation choice in ACL reconstruction. This study also provides new reference data for the operated and non-operated knees of patients following hamstring autograft ACL reconstruction.

Level of evidence: Level 1 prospective, double-blinded, randomized controlled trial.

Trial registration: NCT03184922 (ClinicalTrials.gov).