Forearm T-score as a predictor of cage subsidence in patients with degenerative lumbar spine disease following posterior single-segment lumbar interbody fusion

Abstract

BackgroundPosterior lumbar interbody fusion (PLIF) has become a classic treatment modality for lumbar degenerative diseases, with cage subsidence as a potentially fatal complication due to low bone mineral density (BMD), which can be measured by forearm T-score. Hounsfield units (HU) derived from computed tomography have been a reliable method for assessing BMD.ObjectiveTo determine the accuracy of forearm T-score in predicting cage subsidence after PLIF compared with lumbar spine HU values.MethodsWe retrospectively analyzed the clinical data of 71 patients who underwent PLIF and divided them into cage subsidence group and nonsubsidence group. The differences in preoperative HU value and forearm T-score were compared between groups, and the correlation between cage subsidence and clinical efficacy was analyzed.ResultsThe subsidence rate for all 71 patients (31 men and 40 women) was 23.9%. There was no significant difference in age, sex ratio, body mass index, smoking status, follow-up time, spine BMD, and spine T-score between groups, except in the forearm T-score and lumbar spine HU values (P < 0.05). The forearm T-score (AUC, 0.840; 95% CI, 0.672–1.000) predicted cage subsidence more accurately than the mean global HU value (AUC, 0.744; 95% CI, 0.544–0.943). In logistic regression analysis, both forearm T-score and mean global HU value were found to be independent risk factors for cage subsidence (P < 0.05).ConclusionsLower forearm T-scores and lower lumbar spine HU values were significantly associated with the occurrence of cage subsidence. Lower forearm T-scores indicated a higher risk of cage subsidence than lumbar spine HU values. Forearm T-score is more effective in predicting cage subsidence than spine T-score. Therefore, forearm dual-energy X-ray absorptiometry may be a fast, simple, and reliable method for predicting cage subsidence following PLIF. However, our results suggest that the degree of cage subsidence is not associated with clinical efficacy.