计算机断层扫描中较低的 Hounsfield 单位值与腰椎侧路椎间融合术后椎间融合器下沉的关系。

The association between lower Hounsfield units on computed tomography and cage subsidence after lateral lumbar interbody fusion.

机构信息

Departments of1Neurosurgery and.

3Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China.

出版信息

Neurosurg Focus. 2020 Aug;49(2):E8. doi: 10.3171/2020.5.FOCUS20169.

DOI:10.3171/2020.5.FOCUS20169

PMID:32738801

Abstract

OBJECTIVE

One vexing problem after lateral lumbar interbody fusion (LLIF) surgery is cage subsidence. Low bone mineral density (BMD) may contribute to subsidence, and BMD is correlated with Hounsfield units (HUs) on CT. The authors investigated if lower HU values correlated with subsidence after LLIF.

METHODS

A retrospective study of patients undergoing single-level LLIF with pedicle screw fixation for degenerative conditions at the University of California, San Francisco, by 6 spine surgeons was performed. Data on demographics, cage parameters, preoperative HUs on CT, and postoperative subsidence were collected. Thirty-six-inch standing radiographs were used to measure segmental lordosis, disc space height, and subsidence; data were collected immediately postoperatively and at 1 year. Subsidence was graded using a published grade of disc height loss: grade 0, 0%-24%; grade I, 25%-49%; grade II, 50%-74%; and grade III, 75%-100%. HU values were measured on preoperative CT from L1 to L5, and each lumbar vertebral body HU was measured 4 separate times.

RESULTS

After identifying 138 patients who underwent LLIF, 68 met the study inclusion criteria. All patients had single-level LLIF with pedicle screw fixation. The mean follow-up duration was 25.3 ± 10.4 months. There were 40 patients who had grade 0 subsidence, 15 grade I, 9 grade II, and 4 grade III. There were no significant differences in age, sex, BMI, or smoking. There were no significant differences in cage sizes, cage lordosis, and preoperative disc height. The mean segmental HU (the average HU value of the two vertebrae above and below the LLIF) was 169.5 ± 45 for grade 0, 130.3 ± 56.2 for grade I, 100.7 ± 30.2 for grade II, and 119.9 ± 52.9 for grade III (p < 0.001). After using a receiver operating characteristic curve to establish separation criteria between mild and severe subsidence, the most appropriate threshold of HU value was 135.02 between mild and severe subsidence (sensitivity 60%, specificity 92.3%). After univariate and multivariate analysis, preoperative segmental HU value was an independent risk factor for severe cage subsidence (p = 0.017, OR 15.694, 95% CI 1.621-151.961).

CONCLUSIONS

Lower HU values on preoperative CT are associated with cage subsidence after LLIF. Measurement of preoperative HU values on CT may be useful when planning LLIF surgery.

摘要

目的

经侧方腰椎椎间融合术（LLIF）后，一个令人困扰的问题是 cage 下沉。低骨密度（BMD）可能导致下沉，而 BMD 与 CT 上的 Hounsfield 单位（HU）相关。作者研究了 LLIF 后较低的 HU 值是否与下沉有关。

方法

对在加利福尼亚大学旧金山分校由 6 位脊柱外科医生进行的单节段 LLIF 伴椎弓根螺钉固定治疗退行性疾病的患者进行回顾性研究。收集了人口统计学、cage 参数、术前 CT 上的 HU 值和术后下沉的数据。使用 36 英寸站立位 X 线片测量节段性前凸、椎间盘间隙高度和下沉；数据在术后即刻和 1 年时收集。使用发表的椎间盘高度丢失分级来分级下沉：0 级，0%-24%；1 级，25%-49%；2 级，50%-74%；3 级，75%-100%。在术前 CT 上从 L1 到 L5 测量 HU 值，并对每个腰椎椎体进行 4 次单独测量。

结果

在确定了 138 例接受 LLIF 的患者后，有 68 例符合研究纳入标准。所有患者均行单节段 LLIF 伴椎弓根螺钉固定。平均随访时间为 25.3±10.4 个月。有 40 例患者存在 0 级下沉，15 例为 1 级，9 例为 2 级，4 例为 3 级。年龄、性别、BMI 或吸烟史无显著差异。 cage 大小、cage 前凸和术前椎间盘高度无显著差异。0 级的平均节段性 HU（LLIF 上下两个椎体的平均 HU 值）为 169.5±45，1 级为 130.3±56.2，2 级为 100.7±30.2，3 级为 119.9±52.9（p<0.001）。使用受试者工作特征曲线确定轻度和重度下沉之间的分离标准后，HU 值的最佳阈值为 135.02（轻度和重度下沉的敏感度为 60%，特异性为 92.3%）。单变量和多变量分析后，术前节段性 HU 值是 cage 重度下沉的独立危险因素（p=0.017，OR 15.694，95%CI 1.621-151.961）。