Early postoperative C-reactive protein-to-albumin ratio for risk stratification of osteomyelitis recurrence after surgical treatment

Reliable biomarkers for identifying patients at increased risk of osteomyelitis recurrence during the early postoperative period are lacking. The C-reactive protein-to-albumin ratio (CAR), which integrates systemic inflammatory burden and nutritional status, has shown diagnostic value in musculoskeletal infections, but its prognostic role after surgical treatment of osteomyelitis remains unclear. This study evaluated whether early postoperative CAR predicts osteomyelitis recurrence and compared its performance with conventional inflammatory biomarkers.

This retrospective cohort study included 90 consecutive adults who underwent surgical treatment for osteomyelitis between January 2020 and December 2024. Serum inflammatory biomarkers were recorded before surgery and at the first postoperative outpatient visit, approximately one month after surgery. The primary outcome was osteomyelitis recurrence during a minimum follow-up of 12 months. Receiver operating characteristic (ROC) analysis was used to evaluate the predictive performance of inflammatory biomarkers, and multivariable logistic regression was used to evaluate factors independently associated with recurrence.

During a mean follow-up of 19 months, recurrence occurred in 19 patients (21.1%). Patients with recurrence had significantly higher baseline and one-month CAR values than those without recurrence (both p < 0.001). Among the evaluated biomarkers, one-month CAR demonstrated the numerically highest AUC for recurrence (AUC = 0.862; optimal cutoff = 1.41), with a sensitivity of 73.7% and specificity of 87.3%. However, its AUC was not significantly different from that of one-month CRP (AUC = 0.831; DeLong p = 0.223). In multivariable analysis, one-month CAR remained independently associated with recurrence within the parsimonious multivariable model (OR 5.42, 95% CI 2.38-12.36; p < 0.001), together with the Charlson Comorbidity Index (OR 1.94, 95% CI 1.27-2.96; p = 0.002). Leukocyte-derived inflammatory indices showed substantially lower prognostic performance during postoperative follow-up.

Early postoperative CAR was associated with osteomyelitis recurrence and showed good discriminative ability, with the numerically highest AUC among the evaluated inflammatory biomarkers. However, its discriminative performance was not statistically superior to that of one-month CRP. CAR may therefore represent a practical adjunctive biomarker for postoperative risk stratification. Prospective multicenter studies are warranted to validate these findings and determine whether CAR-guided surveillance improves patient outcomes.