Objective:

To investigate the correlation between CT value and Cage subsidence in patients with lumbar degenerative disease treated with stand-alone oblique lumbar interbody fusion (OLIF).

Methods:

The clinical data of 35 patients with lumbar degenerative diseases treated with stand-alone OLIF between February 2016 and October 2018 were retrospectively analyzed. There were 15 males and 20 females; the age ranged from 29 to 81 years, with an average of 58.4 years. There were 39 operative segments, including 32 cases of single-segment, 2 cases of double-segment, and 1 case of three-segment. Preoperative lumbar CT was used to measure the CT values of the axial position of L ₁ vertebral body, the axial and sagittal positions of L _1-4 vertebral body, surgical segment, and the axial position of upper and lower vertebral bodies as the bone mineral density index, and the lowest T value was recorded by dual-energy X-ray absorptiometry. The visual analogue scale (VAS) and Oswestry disability index (ODI) scores were recorded before operation and at last follow-up. At last follow-up, the lumbar interbody fusion was evaluated by X-ray films of the lumbar spine and dynamic position; the lumbar lateral X-ray film was used to measure the subsidence of the Cage, and the patients were divided into subsidence group and nonsubsidence group. The univariate analysis on age, gender, body mass index, lowest T value, CT value of vertebral body, disease type, and surgical segment was performed to initially screen the influencing factors of Cage subsidence; further the logistic regression for multi-factor analysis was used to screen fusion independent risk factors for Cage subsidence. The receiver operating characteristic (ROC) curve and area under curve (AUC) were used to analyze the CT value and the lowest T value to predict the Cage subsidence. Spearman correlation analysis was used to determine the correlation between Cage subsidence and clinical results.

Results:

All the 35 patients were followed up 27-58 months, with an average of 38.7 months. At last follow-up, the VAS and ODI scores were significantly decreased when compared with preoperative scores ( t=32.850, P=0.000; t=31.731, P=0.000). No recurrent lower extremity radiculopathy occurred and no patient required revision surgery. Twenty-seven cases (77.1%) had no Cage subsidence (nonsubsidence group); 8 cases (22.9%) had at least radiographic evidence of Cage subsidence, the average distance of Cage subsidence was 2.2 mm (range, 1.1-4.2 mm) (subsidence group). At last follow-up, there was 1 case of fusion failure both in the subsidence group and the nonsubsidence group, there was no significant difference in the interbody fusion rate (96.3% vs. 87.5%) between two groups ( P=0.410). Univariate analysis showed that the CT value of vertebral body (L ₁ axial position, L _1-4 axial and sagittal positions, surgical segment, and upper and lower vertebral bodies axial positions) and the lowest T value were the influencing factors of Cage subsidence ( P<0.05). According to ROC curve analysis, compared with AUC of the lowest T value [0.738, 95% CI (0.540, 0.936)], the AUC of the L _1-4 axis CT value was 0.850 [95% CI (0.715, 0.984)], which could more effectively predict Cage subsidence. Multivariate analysis showed that the CT value of L _1-4 axis was an independent risk factor for Cage subsidence ( P<0.05).

Conclusion:

The CT value measurement of the vertebral body based on lumbar spine CT before stand-alone OLIF can predict the Cage subsidence. Patients with low CT values of the lumbar spine have a higher risk of Cage subsidence. However, the Cage subsidence do not lead to adverse clinical results.

目的:

探讨腰椎椎体CT值与单纯斜外侧腰椎间融合术（oblique lumbar interbody fusion，OLIF）治疗退变性腰椎疾病中融合器下沉的关系。.

方法:

回顾分析2016年2月—2018年10月采用单纯OLIF治疗的35例腰椎退变性疾病患者临床资料。男15例，女20例；年龄29～81岁，中位年龄 58 岁。手术节段39个，其中单节段32例，双节段2例，三节段1例。采用术前腰椎CT测量L ₁椎体轴位、L _1～4椎体轴位和矢状位、手术融合节段及上下椎体轴位CT值作为骨密度指标，同时采用双能X线吸收测定法记录最低T值。记录术前和末次随访时疼痛视觉模拟评分（VAS）和Oswestry功能障碍指数（ODI）评分；末次随访时通过腰椎正侧位和动力位X线片评价腰椎间融合。末次随访时采用腰椎侧位X线片测量融合器下沉，并将患者分为下沉组和非下沉组。对年龄、性别、身体质量指数、最低T值、椎体CT值、疾病类型、手术节段进行单因素分析，初步筛选融合器下沉的影响因素；进一步采用logistic回归进行多因素分析，筛选融合器下沉的独立危险因素。采用 ROC 曲线和曲线下面积（area under curve，AUC）分析CT值和最低T值预测融合器下沉。采用Spearman相关分析判断融合器下沉与临床结果的相关性。.

结果:

患者均获随访，随访时间27～58个月，平均38.7个月。末次随访时，患者VAS评分和ODI评分均较术前显著下降（ t=32.850， P=0.000； t=31.731， P=0.000）。无下肢神经症状复发患者，无1例患者行翻修手术。27例（77.1%）未发生融合器下沉（非下沉组）；8例（22.9%）发生融合器下沉1.1～4.2 mm，平均2.2 mm（下沉组）。末次随访时，下沉组和非下沉组分别有1例腰椎间未融合，两组椎间融合率（96.3% vs. 87.5%）比较差异无统计学意义（ P=0.410）。单因素分析显示，椎体CT值（L ₁ 轴位、L _1～4 轴位和矢状位、手术节段及上下椎体轴位）和最低T值是融合器下沉的影响因素（ P<0.05）。根据ROC曲线分析，与最低T值AUC 0.738 ［95% CI（0.540，0.936）］相比，L _1～4轴位CT值的AUC为0.850 ［95% CI（0.715，0.984）］，可更加有效预测融合器下沉。多因素分析显示，L _1～4轴位CT值是融合器下沉的独立危险因素（ P<0.05）。.

结论:

拟行单纯OLIF前进行基于腰椎CT的椎体CT值测量可预测融合器下沉风险，腰椎椎体低CT值患者有较高融合器下沉风险，但融合器下沉并未导致不良临床结果。.