OBJECTIVE Postoperative subsidence of transforaminal lumbar interbody fusion (TLIF) cages can result in loss of lordosis and foraminal height, and potential recurrence of nerve root impingement. The objectives of this study were to determine factors associated with TLIF cage subsidence. Specifically, the authors sought to determine if preoperative disc height compared to cage height could be used to predict TLIF interbody cage subsidence, and if decreased postoperative vertebral Hounsfield units (HUs) predisposed to cage subsidence. METHODS The authors retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. The preoperative disc height was measured for the operative and adjacent-level disc on MRI. The difference between cage and disc heights was measured and compared between the subsidence and nonsubsidence groups. The average HUs of the L1 vertebral body were measured on CT scans. RESULTS Eighty-nine patients were identified with complete imaging and follow-up information. Forty-five patients (50.6%) had evidence of interbody cage subsidence on follow-up CT. The average cage subsidence was 5.5 mm (range 2.2–10.8 mm). The average implant height was significantly higher in the subsidence group compared to the nonsubsidence group (12.6 vs 11.2 mm). Additionally, the difference between cage height and preoperative adjacent-level disc height was also significantly larger in the subsidence group (3.8 vs 1.2 mm). First lumbar vertebral body (L1) HUs were significantly higher in the nonsubsidence versus the subsidence group (167.8 vs 137.71 HUs, p = 0.002). Multivariate logistic regression analysis identified suprajacent disc height and L1 HUs to be independent predictors of interbody cage subsidence. Receiver operating characteristic curves identified a suprajacent to cage height difference 1.3 mm to have a 93.3% sensitivity for cage subsidence. CONCLUSIONS This study is the first of its kind to demonstrate the association between vertebral body HUs and suprajacent disc height with the development of interbody cage subsidence after TLIF. The authors found that patients with lower HUs in the L1 vertebral body were more likely to experience subsidence, regardless of surgical level. Additionally, the study demonstrated that interbody cage height 1.3 mm above the height of the suprajacent level is an independent risk factor for cage subsidence, with 93.3% sensitivity. These findings suggest that these factors may be utilized to create a template preoperatively for intraoperative cage selection.
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机译：突然腰椎胸椎椎体椎体椎间体融合（TLIF）笼养的目的术后沉降可能导致脊柱病和热神经元的丧失，以及神经根部冲击的潜在复发。本研究的目标是确定与TLIF笼沉降相关的因素。具体而言，作者试图确定与笼高相比的术前盘高度是否可用于预测TLIF椎体剧本沉降，如果术后椎体Hounsfield单位（HUS）倾向于笼沉降。方法提交人回顾性地审查了2004年7月至2014年6月之间的两个机构接受了仪器TLIF的所有患者。在MRI上测量术前盘高度和相邻级盘。测量笼和盘高度之间的差异，并在沉降和非管道组之间进行比较。在CT扫描上测量L1椎体的平均HUS。结果以完整的成像和后续信息确定八十九名患者。四十五名患者（50.6％）有跨越车鼠沉降的证据。平均笼沉降为5.5毫米（范围2.2-10.8毫米）。与非管制组（12.6 Vs 11.2mm）相比，沉降组平均植入物高度显着高。另外，在沉降组中，笼高度和术前相邻级盘高度的差异也显着较大（3.8 Vs 1.2 mm）。第一腰椎体（L1）HUS在非沉降组（167.8 VS 137.71 HUS，P = 0.002）中显着高。多变量逻辑回归分析确定了Supra附带的光盘高度和L1 HUS，是跨越互笼沉降的独立预测因子。接收器操作特性曲线识别出笼高度差> 1.3毫米，持续93.3％的灵敏度。结论本研究是首先，以便在TLIF之后展示椎体HUS和SUPRA附庸的椎间盘高度之间的关联。作者发现，无论手术水平如何，L1椎体在L1椎体中较低的患者更可能经历沉降。此外，该研究表明，上方笼笼高度> 1.3毫米高于超中心水平的高度是笼沉降的独立危险因素，灵敏度为93.3％。这些发现表明这些因素可用于术前用于术中持续选择的模板。
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