Is There a Hamstring Autograft Diameter Threshold for Anterior Cruciate Ligament Reconstruction?

Hamstring autograft (HA) is a popular graft for anterior cruciate ligament reconstruction (ACLR). Although multiple studies have demonstrated that increasing the graft diameter decreases the risk of failure or revision surgery, the exact minimum graft diameter remains controversial, with the unofficial standard being 8 mm.

To evaluate the risk of aseptic revision after HA-ACLR in patients aged ≤25 years, comparing graft diameters of (1) <8 versus ≥8 mm and (2) ≤8 versus >8 mm. A secondary purpose was to determine whether there was a threshold for graft diameter that best identifies patients at a higher risk of aseptic revision.

Cohort study; Level of evidence, 3.

A total of 5972 primary HA-ACLRs were identified using data from the ACLR registry of Kaiser Permanente. Propensity score-weighted Cox regression was used to evaluate revision risk for HAs with <8 versus ≥8 mm diameter and with ≤8 versus >8 mm diameter. An effect plot and receiver operating characteristic curve and area under the curve (AUC) analysis were also created to model the probability of revision based on the HA diameter to determine whether there was a specific diameter threshold to minimize revision risk.

In the propensity score-weighted Cox model, <8 mm autografts had a higher risk of aseptic revision compared with ≥8 mm autografts (hazard ratio [HR], 1.32 [95% CI, 1.01-1.71]; P = .039); a higher risk was also observed when comparing ≤8 to >8 mm grafts (HR, 1.32 [95% CI, 1.06-1.66]; P = .015). In receiver operating characteristic analysis, an HA diameter that best identified patients at a higher risk for revision after ACLR could not be identified (AUC, 0.56). However, the adjusted effect plot showed a direct decrease in revision risk with each increasing increment in graft size.

A 32% higher risk of revision was observed in smaller graft diameter groups (<8 or ≤8 mm) compared with larger graft sizes (≥8 or >8 mm), regardless of specific diameter cutoff. In a cohort of almost 6000 HA-ACLR, the authors were unable to determine a definitive minimum graft diameter threshold that should be used.