Postoperative HbA1c within the non-diabetic range is not associated with systemic inflammation indices following anterior cruciate ligament reconstruction

BACKGROUND: Glycated hemoglobin (HbA1c), a marker of long-term glycemic control, has been linked to adverse outcomes following anterior cruciate ligament reconstruction (ACLR). Systemic indices of the immune system and inflammation derived from routine blood counts serve as prognostic tools in various clinical contexts. While HbA1c and systemic indices of inflammation have been independently associated with post-surgery complications, their relationship following ACLR remains unclear. The purpose of this study was to evaluate whether elevated HbA1c levels are associated with increased systemic inflammation and complications following ACLR. METHODS: This retrospective case-control study consisted of patients who underwent ACLR with HbA1c and complete blood counts (CBCs) with differentials obtained ≥90 days after surgery. Patients were separated into two groups: controls (HbA1c <5.7%; n = 59) and cases (HbA1c ≥5.7%; n = 14). Controls were matched to cases (≥2:1) based on age and BMI. Systemic indices of the immune system and inflammation (i.e., systemic immune-inflammation index (SII), platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR), pan-immune-inflammation value (PIV), monocyte-to-lymphocyte ratio (MLR), and systemic inflammation response index (SIRI)) were derived from CBCs. RESULTS: No cases displayed an HbA1c >6.4% (range 5.7-6.4%). Systemic indices of the immune system and inflammation were not significantly different between controls and cases (p = 0.117-0.933). HbA1c was not significantly correlated with NLR, MLR, PLR, SII, SIRI, and PIV (all p > 0.05), and regression models confirmed no associations. Five complications occurred, with no significant difference in complication frequency between groups (p = 1.000). HbA1c did not differ significantly between patients with and without complications (p = 0.511). CONCLUSION: Following ACLR, elevated HbA1c was not associated with systemic inflammation or postoperative complications. These preliminary findings suggest limited utility of HbA1c values below the diabetic threshold for risk stratification in patients that underwent ACLR. Further study in patients with higher HbA1c values is warranted.