Pennington Zach, Kumar Rahul, Hamouda Abdelrahman, Martini Michael, Mikula Anthony L, Astudillo Potes Maria, Bydon Mohamad, Clarke Michelle J, Krauss William E, Nassr Ahmad N, Freedman Brett A, Sebastian Arjun S, Fogelson Jeremy L, Elder Benjamin D
Departments of1Neurologic Surgery and.
3Department of Neurosurgery, University of California, San Francisco, California.
J Neurosurg Spine. 2025 May 9;43(1):42-51. doi: 10.3171/2025.1.SPINE24923. Print 2025 Jul 1.
Transforaminal lumbar interbody fusion (TLIF) offers both indirect decompression and segmental correction through restoration of disc height. However, stresses exerted on the vertebral endplates by the interbody device can result in implant subsidence and loss of correction. The present time-to-event analysis aimed to identify predictors of interbody subsidence.
Patients who underwent 1- or 2-level TLIF were identified. Data on demographics, surgical details, preoperative bone quality using CT-based Hounsfield units (HU), and pre- and postoperative lumbopelvic parameters were collected. Univariable analyses were conducted to identify predictors of subsidence (≥ 2-mm intrusion of interbody into cranial or caudal vertebrae) and significant subsidence (≥ 4-mm intrusion). Multivariable Cox regression was performed to identify independent predictors of subsidence, expressed as hazard ratios with 95% confidence intervals.
A total of 198 patients treated at 241 levels were included (median age 66.6 years, IQR 59.5, 73.7 years; 56.6% were women). In 92 levels (38.2%) there was some subsidence and in 25 (10.4%) there was significant subsidence. Implanted levels demonstrating subsidence (≥ 2 mm) were associated with lower HU in cranial and caudal vertebrae; had interbodies positioned farther from the anterior apophyseal ring; were implanted with taller, more lordotic interbodies; and underwent greater disc height restoration. Those showing significant subsidence (≥ 4 mm) were similarly associated with lower HU in the cranial and caudal vertebrae; had interbodies positioned farther from the anterior apophyseal ring of the caudal vertebrae; and underwent greater disc height restoration. Multivariable Cox regression showed that time to subsidence was predicted by greater implant height (HR 1.20/mm, 95% CI 1.05-1.38; p = 0.009), greater postoperative disc height (HR 1.21/mm, 95% CI 1.09-1.34; p < 0.001), and greater disc height restoration (HR 1.11/mm, 95% CI 1.04-1.19; p = 0.002). The time-to-subsidence analysis for significant (≥ 4 mm) subsidence showed that it was predicted by lower HU in the cranial vertebrae (HR 0.98/unit, 95% CI 0.97-0.99; p = 0.001); increasing number of levels instrumented (HR 1.26, 95% CI 1.04-1.52; p = 0.016); and greater disc height restoration (HR 1.33/mm, 95% CI 1.18-1.51; p < 0.001).
This time-to-event analysis suggests that interbody subsidence following TLIF is best predicted by implantation of a taller interbody and aggressive disc height restoration. Significant subsidence is similarly predicted by aggressive disc height restoration along with poor baseline bone quality. The results suggest the need to balance aggressive correction at the time of surgery against the increased risk of subsequent interbody subsidence.
经椎间孔腰椎椎体间融合术（TLIF）通过恢复椎间盘高度实现间接减压和节段性矫正。然而，椎间融合器对椎体终板施加的应力可导致植入物下沉和矫正丢失。本次生存分析旨在确定椎间融合器下沉的预测因素。
纳入接受单节段或双节段TLIF手术的患者。收集患者人口统计学资料、手术细节、基于CT的Hounsfield单位（HU）评估的术前骨质以及术前和术后腰骶骨盆参数。进行单因素分析以确定下沉（椎间融合器向头侧或尾侧椎体侵入≥2 mm）和显著下沉（侵入≥4 mm）的预测因素。进行多因素Cox回归分析以确定下沉的独立预测因素，并以95%置信区间的风险比表示。
共纳入241个节段接受治疗的198例患者（中位年龄66.6岁，四分位间距59.5，73.7岁；56.6%为女性）。92个节段（38.2%）出现一定程度的下沉，25个节段（10.4%）出现显著下沉。出现下沉（≥2 mm）的植入节段与头侧和尾侧椎体较低的HU值相关；椎间融合器距离前侧骨突环更远；植入更高、更具前凸的椎间融合器；并且椎间盘高度恢复更大。出现显著下沉（≥4 mm）的节段同样与头侧和尾侧椎体较低的HU值相关；椎间融合器距离尾侧椎体的前侧骨突环更远；并且椎间盘高度恢复更大。多因素Cox回归分析显示，植入物高度增加（风险比1.20/mm，95%置信区间1.05 - 1.38；p = 0.009）、术后椎间盘高度增加（风险比1.21/mm，95%置信区间1.09 - 1.34；p < 0.001）以及椎间盘高度恢复增加（风险比1.11/mm，95%置信区间1.04 - 1.19；p = 0.002）可预测下沉时间。显著下沉（≥4 mm）的生存分析显示，头侧椎体较低的HU值（风险比0.98/单位，95%置信区间0.97 - 0.99；p = 0.001）、固定节段数量增加（风险比1.26，95%置信区间1.04 - 1.52；p = 0.016）以及椎间盘高度恢复增加（风险比1.33/mm，95%置信区间1.18 - 下）可预测下沉时间。
本次生存分析表明，TLIF术后椎间融合器下沉最好通过植入更高的椎间融合器和积极的椎间盘高度恢复来预测。积极的椎间盘高度恢复以及基线骨质较差同样可预测显著下沉。结果表明，手术时需要在积极矫正与随后椎间融合器下沉风险增加之间取得平衡。
