Does pre-operative metabolic and nutritional assessment have greater association with perioperative complications than frailty following surgical intervention for proximal humerus fractures?

Background: Proximal humerus fractures (PHFs) often occur in an elderly population at-risk for complications following surgery. However, it is unknown whether acute pre-operative metabolic and nutritional (M + N) variables vs. more chronic frailty evaluation is better linked to these poor outcomes. The purpose of this study is to compare the associations of the M + N index vs. frailty with the outcomes of surgical intervention for PHFs. Methods: A patient-deidentified national database was queried from 2015 to 2020 for patients undergoing surgical management of PHFs. Tiered frailty scores were calculated as defined by the revised Risk Analysis Index (RAI). The M + N index was derived using backward stepwise logistic regression modeling to identify pre-operative nutritional and metabolic lab values associated with development of any complication following surgery. Outcomes included 30-day mortality, readmission, length of stay, and complications. Analysis of variance and binary logistic regression were used to assess associations with odds ratio and 95% confidence interval. Discriminatory accuracy was quantified by receiver operating characteristic curve analysis and C-statistics. Results: A total of 6,020 patients with PHFs underwent surgical intervention (67% open reduction and internal fixation, 33% reverse total shoulder arthroplasty). The generated M + N index was composed of the following variables significantly associated with complications: creatinine, albumin, hematocrit, international normalized ratio, and sodium. The M + N index had superior predictability to RAI for any complication (area under the curve [AUC]: 0.749 vs. 0.674), post-operative blood transfusion (AUC: 0.812 vs. 0.704), length of stay greater than 3 days (0.901 vs. 0.679), and reoperation (AUC: 0.656 vs. 0.542), with each significant association also seen in a frail-only cohort. In a mixed-effects model, M + N index factors and RAI generated independent significant effects (both P < .001). Discussion: While frailty assessment may play a role in evaluating pre-operative risk and informing optimization strategies, preoperative M + N status has greater association with perioperative complications and disposition following surgery for PHFs. These values may also be more readily optimized in the inpatient setting; therefore, future studies should focus on the effects of implementing management strategies to alter M + N status prior to surgical intervention and potentially mitigate perioperative risk.