Temporal and spatial graft maturation patterns and associated factors after double-bundle anterior cruciate ligament reconstruction: A retrospective cohort study.

Abstract

Graft maturation after anterior cruciate ligament reconstruction is not uniform, but bundle- and segment-specific patterns after double-bundle reconstruction (DB-ACLR) remain poorly characterised. Factors associated with 2-year graft SNQ, including graft geometry, have not been fully established. In this retrospective cohort study, patients who underwent primary DB-ACLR with hamstring autografts were included. Postoperative magnetic resonance imaging (MRI) was performed at approximately 6 months, 1 year, and 2 years using a sagittal fat-saturated proton density-weighted sequence. The signal-to-noise quotient (SNQ) was measured separately for the anteromedial bundle (AMB) and posterolateral bundle (PLB), each divided into proximal, middle, and distal segments. Factors associated with 2-year SNQ were examined using multivariable linear regression. Patient-reported outcome measures (PROMs) were collected at 2 years. Of 472 screened patients, 167 had MRI suitable for SNQ analysis. After excluding 19 with graft failure within 2 years, 148 patients with intact grafts comprised the analysis cohort; 74 with MRI at all three time points formed the longitudinal subgroup. The PLB had consistently higher SNQ than the AMB at all time points (all P < 0.001). Distal segments showed increasing SNQ over time. Greater graft inclination angle was independently associated with lower 2-year SNQ in both bundles (AMB: B = -0.43 per 1°; PLB: B = -0.47 per 1°; both P < 0.001). No correlation was found between 2-year SNQ and PROMs. Graft maturation after DB-ACLR was heterogeneous across bundles and segments. SNQ was consistently higher in the PLB than the AMB, and distal-segment SNQ increased over time, reaching significance in the PLB. A greater graft inclination angle was independently associated with lower 2-year SNQ, whereas 2-year SNQ was not correlated with PROMs.