Graft diameter does not affect re-rupture rates or clinical outcomes in double-bundle anterior cruciate ligament reconstruction.

Abstract

While a graft diameter of less than 8 mm is considered a risk factor for re-rupture in single-bundle anterior cruciate ligament reconstruction (ACLR), no studies have investigated the threshold for risk in double-bundle ACLR (DB-ACLR). This study aimed to evaluate the relationship between graft diameter and re-rupture rates in DB-ACLR. This study included 589 knees that underwent DB-ACLR with a minimum follow-up of 2 years. The total cross sectional area (CSA) of the grafts was calculated from the diameters of the anteromedial bundle (AMB) and posterolateral bundle (PLB). A restricted cubic spline regression model was applied to evaluate the relationship between total CSA and graft re-rupture. Although no statistically significant cutoff value was identified, the analysis suggested potential differences in re-rupture rates between knees with extremely small or large CSAs. Based on this finding, knees were classified into two groups: Group S (total CSA < 39 mm², corresponding to a single-bundle diameter < 7 mm) and Group L (total CSA > 50 mm², corresponding to a single-bundle diameter > 8 mm). Propensity score matching was conducted to adjust for confounding factors, including age, height, and weight, and re-rupture rates and Knee injury and Osteoarthritis Outcome Score (KOOS) were compared between the groups. Graft re-rupture was observed in 37 out of 589 knees (6.3%). The mean graft diameter was 5.3 ± 0.4 mm for AMB, 5.0 ± 0.4 mm for PLB, and 41.5 ± 7.1 mm² for total CSA. Restricted cubic spline regression analysis showed a slight decrease in the log odds of re-rupture with increasing CSA, but no significant cutoff value was identified, and the observed trend was not statistically significant. After propensity score matching, there were no significant differences in re-rupture rates (13.5% in Group S vs. 8.1% in Group L, p = 0.71) or KOOS scores between the groups. In DB-ACLR, no clear cutoff value for graft diameter was identified, and total CSA was not a significant risk factor for re-rupture. Knees with small-diameter grafts demonstrated comparable re-rupture rates and KOOS scores to those with larger-diameter grafts. Level III.