后路腰椎椎体间融合术后融合器脱出的危险因素分析

【摘要】 目的：探讨腰椎椎体间融合内固定术后融合器脱出（cage retropulsion，CR）的危险因素。方法：回顾性分析2017年9月~2021年9月在我院因腰椎椎体间融合内固定术后CR行翻修手术的17例患者，其中男13例，女4例，年龄63.7±9.9岁，纳入CR组。根据相同的融合及固定节段、初次手术时间（±1年）、性别、年龄（±2岁）在无融合器脱出及移位的患者中按照2∶1的比例进行配对共匹配34例作为对照组，其中男26例，女8例，年龄65.2±10.2岁。CR组初次手术平均固定节段数为1.8±0.8个，融合节段数为1.5±0.6个；发现CR距离初次手术时间为7个月（0.75~132个月）；17例患者中单个节段CR 15例，两个节段CR 2例。在两组患者术前全脊柱X线片上测量腰椎前凸角（lumbar lordosis，LL）、骨盆倾斜角（pelvic tilt，PT）、骶骨倾斜角（sacral slope，SS）、骨盆入射角（pelvic incidence，PI）、腰椎侧位X线片上测量病变节段椎间高度（disc height，DH）、屈伸位X线片上测量椎间隙活动度（range of motion，ROM）；通过术前腰椎CT检查测量腰椎椎体CT值；通过腰椎MRI检查定义椎间盘形态；在术后即刻腰椎X线片上测量融合器位置（融合器后缘标记线到下位椎体后上缘的距离与下位椎体上终板前后径的比值）。采用配对样本t检验的方法对两组间资料进行单因素分析，对单因素分析有统计学意义的参数进行Logistic回归分析，寻找CR的独立危险因素。结果：CR组椎体CT值小于对照组（124.8±39.7 vs 147.7±38.2, P=0.011），术后即刻X线片上融合器位置较对照组更靠后（0.15±0.09 vs 0.31±0.07， P<0.001）；两组间术前LL（40.8°±12.9° vs 42.4°±7.5°，P=0.717）、PT（19.6°±7.1° vs 17.1°±6.7°，P=0.356）、SS（27.7°±6.5° vs 31.0°±4.3°，P=0.144）、PI（44.3°±13.8° vs 44.7°±13.9°，P=0.926）、DH（10.1±2.4mm vs 8.8±1.4mm，P=0.066）、ROM（4.3°±2.8° vs 4.4°±2.2°，P=0.950）、梨形椎间盘比例（33.3% vs 21.4%，P=0.40）均无统计学差异。Logistic回归分析结果提示椎体CT值低（骨质疏松）（OR=0.975，P=0.043）和融合器位置靠后（OR=28.393，P=0.003）是CR的独立危险因素。结论：骨质疏松与融合器放置靠后是后路腰椎椎体间融合术后CR的危险因素。

Analysis of risk factors of cage retropulsion after posterior lumbar interbody fusion

【Abstract】 Objectives: To investigate the risk factors of cage retropulsion(CR) after posterior lumbar interbody fusion(PLIF). Methods: Retrospective analysis was made on 17 patients(13 males and 4 females, with an average age of 63.7±9.9 years) who underwent revision surgery due to CR after PLIF in our hospital from September 2017 to September 2021. And the patients were included into the CR group. Another 34 patients without CR were matched in a ratio of 2∶1 according to the same fusion and fixation segments, time of initial surgery(±1 year), gender, and age(±2 years), including 26 males and 8 females, with an average age of 65.2±10.2 years. They were included in the control group. In the CR group, the average number of fixed segments was 1.8±0.8, and the average number of fused segments was 1.5±0.6; The time of CR was 7(0.75-132) months after the first operation; 15 patients had single segmental CR and 2 patients had two segmental CR. The lumbar lordosis(LL), pelvic tilt(PT), sacral slope(SS), and pelvic incidence(PI) were measured on full-spine X-ray before operation of the two groups of patients, the disc height(DH) of the diseased segment was measured on lateral lumbar X-ray, and the intervertebral range of motion(ROM) was measured on flexion-extension X-ray. The CT value of lumbar vertebrae was measured in CT examination before operation; The shape of disc was defined through MRI examination. The cage position was measured on X-ray immediately after operation(The ratio of the distance between the marker line of the posterior margin of the cage and the posterior upper margin of the lower vertebral body to the length of the upper endplate of the lower vertebra). The paired sample t-test was used for single factor analysis to analyze the data of the two groups, after which, the parameters with statistical significance were analyzed with logistic regression to determine the independent risk factors of CR. Results: The mean vertebral CT value in the CR group was lower than that in the control group(124.8±39.7 vs 147.7±38.2, P=0.011); The cage position in the CR group was more posterior than that in the control group(0.15±0.09 vs 0.31±0.07, P<0.001). There was no significant difference between the two groups in LL(40.8°±12.9° vs 42.4°±7.5°, P=0.717), PT(19.6°±7.1° vs 17.1°±6.7°, P=0.356), SS(27.7°±6.5° vs 31.0°±4.3°, P=0.144), PI(44.3°±13.8° vs 44.7°±13.9°, P=0.926), DH(10.1±2.4mm vs 8.8±1.4mm, P=0.066), ROM(4.3°±2.8° vs 4.4°±2.2°, P=0.950), and Pear-shaped intervertebral discs(33.3% vs 21.4%, P=0.40). Logistic regression analysis showed that low vertebral CT value(osteoporosis)(OR=0.975, P=0.043) and cage position(OR=28.393, P=0.003) were the independent risk factors. Conclusions: Osteoporosis and posterior placement of cage are the risk factors for CR after PLIF.