Association between preoperative prognostic nutritional index and perioperative outcomes after unicompartmental knee arthroplasty for medial knee osteoarthritis: A retrospective single-center study

This study aims to investigate the association between preoperative Prognostic Nutritional Index (PNI) and short-term clinical outcomes – including 30-day complications and readmission – after unicompartmental knee arthroplasty (UKA) in patients with medial compartment knee osteoarthritis (KOA). This was a retrospective single-center study, enrolling patients aged ≥60 years with medial KOA who underwent UKA between January 2022 and December 2024. The main outcomes were 30-day postoperative complications, length of hospital stay, and unplanned readmission within 30 days after surgery. Demographic, clinical, and laboratory data were collected. The optimal PNI cutoff was determined using a generalized additive model for the risk of overall complications, whereby patients were divided into low and high PNI groups. Multivariate analyses of the relationship between PNI and postoperative outcomes were adjusted for demographic and clinical covariates identified through univariate analysis ( P <.10) and those deemed clinically relevant based on evidence from prior studies. Of the 507 patients (36.1% male, mean age 65.0 ± 3.5 years), 52 (10.3%) experienced complications within 30 days postoperatively, and 20 (3.9%) were readmitted. The most common complications were wound-healing problems (3.2%), deep venous thrombosis (2.4%), and surgical site infection (1.8%). The optimal PNI cutoff was 48.9. Patients with PNI <48.9 had significantly higher risks of overall complications (OR = 2.28, 95% CI: 1.11–4.67; P = .025) and readmission (OR = 4.84, 95% CI: 1.78–13.13; P = .002) compared to those with higher PNI. No significant difference in total or postoperative length of stay was observed between groups. Lower preoperative PNI is independently associated with increased risk of postoperative complications and readmission after UKA in patients with medial KOA. Routine preoperative assessment of PNI may aid in identifying high-risk patients and optimizing perioperative care to improve clinical outcomes.