HIGH PREOPERATIVE CONTROLLING NUTRITIONAL STATUS (CONUT) SCORE PREDICTS FAILURE AND MORTALITY IN ACUTE PERIPROSTHETIC JOINT INFECTION

Aim Host-related factors are increasingly recognised as key determinants of outcome in periprosthetic joint infection (PJI), yet objective and clinically applicable tools to assess host vulnerability remain limited. The Controlling Nutritional Status (CONUT) score reflects immunonutritional status through serum albumin, lymphocyte count, and cholesterol. This study evaluated whether preoperative CONUT predicts failure and mortality after surgery for acute PJI. Methods We performed a single-centre retrospective cohort study of patients surgically treated for acute postoperative or acute haematogenous hip or knee PJI (2013–2024), defined according to European Bone and Joint Infection Society. Minimum follow-up was 12 months. Patients were classified as low or high CONUT (≥5). Outcomes were assessed using the Musculoskeletal Infection Society Outcome Reporting Tool (MSIS-ORT). Infection-related failure was defined as persistent or recurrent infection requiring further treatment (tiers 3B–3F), while overall failure additionally included all-cause death within 1 year (tier 4A). Mortality at final follow-up was analysed separately. Multivariable logistic and Cox regression analyses were performed. Results Ninety patients were included; 42 (46.7%) had high CONUT. These patients were older (80.0 vs 73.6 years) and more frequently classified as McPherson host grade C (45.2% vs 16.7%). Median follow-up was 46.5 months. Infection-related failure occurred in 22.2%, overall failure in 33.3%, and overall mortality in 41.1%. High-CONUT patients had markedly worse outcomes, with higher overall failure (57.1% vs 12.5%) and mortality (61.9% vs 22.9%). They also more frequently presented with Staphylococcus aureus infection (47.6% vs 27.1%) and positive blood cultures (40.5% vs 12.5%), consistent with a more severe infectious phenotype. In multivariable analysis, high CONUT and diabetes mellitus were independently associated with both infection-related failure (OR 4.24 and 3.81, respectively) and overall failure (OR 9.57 and 9.62, respectively), while fracture/revision indication was also associated with overall failure (OR 3.78). In survival analysis, high CONUT independently predicted mortality (HR 2.73; p=0.008), alongside age (HR 1.13 per year; p<0.001), diabetes (HR 3.43; p=0.001), and fracture/revision indication (HR 2.26; p=0.03). Each 1-point increase in CONUT was associated with a 34% increase in mortality risk (HR 1.34; p<0.001), and survival was significantly reduced in high-CONUT patients (log-rank p<0.001). Conclusions Preoperative CONUT identifies patients at markedly increased risk of failure and death after surgery for acute PJI. As a simple and widely available composite marker, it may support preoperative risk stratification and guide clinical decision-making in this high-risk population.