Preoperative geriatric nutritional risk index is a reliable tool for predicting postoperative adjacent segment disease among elderly patients with degenerative lumbar diseases: a case control study

Adjacent segment disease (ASD) is a frequent complication following spinal fusion surgery, particularly prevalent in elderly patients. The nutritional status of elderly patients is also closely related to postoperative outcomes. However, the relationship between nutritional status and the incidence of ASD after spinal surgery remains unknown. This research uniquely evaluates the predictive value of the Geriatric Nutritional Risk Index (GNRI) concerning the development of postoperative ASD in elderly individuals (aged 65 years and above) who underwent transforaminal lumbar interbody fusion (TLIF) for degenerative lumbar disorders. A retrospective study was conducted to assess the outcomes of TLIF in elderly patients with lumbar degenerative disease between 2016 and 2022. Based on the presence or absence of ASD, patients were categorized into the ASD group and the non-ASD group. Demographic, radiographic, and laboratory data were collected. The GNRI was calculated using the baseline serum albumin level and body weight. Univariate and multivariate logistic regression were employed to identify potential preoperative risk factors for ASD. Additionally, a receiver operating characteristic (ROC) curve was utilized to determine the optimal cutoff values of risk factors for predicting ASD. A total of 216 patients (aged 69.67 ± 3.46 years) were included in the analysis, of whom 39(18.1%) developed ASD. The mean GNRI was 102.91 ± 7.42 in the non-ASD group and 95.01 ± 7.95 in the ASD group (p๤0.001). On multivariate logistic regression, GNRI was an independent factor in the prediction of ASD following TLIF, and susceptibility to ASD increases significantly with low GNRI (OR 0.88; 95%CI: 0.81 ~ 0.97; p = 0.007). On the receiver operating characteristic curve, the area under the curve (AUC) for GNRI was 0.802 (95%CI: 0.718 ~ 0.887), significantly higher than that of Alb (AUC = 0.675, 95%CI: 0.582 ~ 0.767, p = 0.007) and BMI (AUC = 0.616, 95%CI: 0.521 ~ 0.710, p = 0.022). The cutoff value for GNRI according to the Youden index was 97.05 (sensitivity: 77.4%, specificity: 69.2%). Our study revealed a significant correlation between lower GNRI scores and the occurrence of ASD following TLIF. Evaluating GNRI prior to TLIF could serve as an effective strategy for predicting ASD risk in elderly patients with degenerative lumbar conditions, thereby facilitating more informed clinical decision-making.