Impact of preoperative nutritional status on morbidity and mortality in elderly patients undergoing spine surgery for metastatic spinal tumors: a role for the Geriatric Nutritional Risk Index

OBJECTIVE: The Geriatric Nutritional Risk Index (GNRI) is commonly used to assess malnutrition risk in elderly patients, but its impact on spine surgery for metastatic spinal tumors is not well understood. This study aimed to evaluate the associations between preoperative nutritional status, as measured by the GNRI, and postoperative morbidity and mortality in elderly patients undergoing spine surgery for metastatic spinal tumors. METHODS: A retrospective cohort study was performed using the 2011-2022 National Surgical Quality Improvement Program database of the American College of Surgeons. Elderly (≥ 65 years of age) patients undergoing laminectomy or corpectomy for extradural spinal tumor metastases were identified using International Classification of Diseases, 9th and 10th Revision and Current Procedural Terminology codes. Patients with missing data on sex, preoperative albumin, height, or weight were excluded. The study population was categorized by GNRI score: normal, malnourished, or severely malnourished. Using receiver operating characteristic (ROC) and multivariable analyses, the authors compared the discriminative thresholds and independent associations of GNRI, the 5-item modified frailty index (mFI-5), and older patient age with any adverse event (AE), extended hospital length of stay (LOS), nonroutine discharge, and 30-day mortality. RESULTS: Of the 659 patients identified, 277 (42.0%) had normal nutritional status, 163 (24.7%) were malnourished, and 219 (33.2%) were severely malnourished. The severely malnourished cohort had significantly increased proportions of electrolyte abnormalities (p = 0.019) and anemia (p < 0.001), with a significant decrease in BMI and albumin levels across cohorts (p < 0.001). Malnourished and severely malnourished patients had significantly longer LOS (9.1 ± 6.2 days and 12.5 ± 8.6 days, respectively, vs 8.6 ± 7.1 days for patients categorized as normal, p < 0.001) and nonroutine discharge (57.9% and 66.7%, respectively, vs 39.7% for normal, p < 0.001). The severely malnourished cohort had significantly increased 30-day mortality (17.4% vs 6.5% for normal and 13.5% for malnourished, p = 0.001). On multivariable analysis, severely malnourished status was independently associated with any AE (adjusted odds ratio [aOR] 1.59, p = 0.036), extended LOS (aOR 2.17, p = 0.001), nonroutine discharge (aOR 1.99, p = 0.001), and 30-day mortality (aOR 2.28, p = 0.013). Malnourished status was independently associated with nonroutine discharge (aOR 1.84, p = 0.005). In ROC analysis, GNRI outperformed the mFI-5 (p = 0.318, p = 0.031, p < 0.009, and p = 0.026, respectively) and patient age (p = 0.018, p < 0.001, p = 0.014, and p = 0.034, respectively) in predicting 30-day AEs, extended LOS, nonroutine discharge, and 30-day mortality. CONCLUSIONS: This study suggests that preoperative GNRI-defined malnutrition is associated with a higher risk of adverse postoperative outcomes in elderly patients undergoing spine surgery for metastatic spinal tumors.