成人退变性脊柱侧凸术后钉棒系统结构特点对上位固定椎骨折的影响研究

The influence of structural characteristics of pedicle screw-rod system on upper instrumented vertebra fracture after surgical treatment of adult degenerative scoliosis

目的分析影像学参数以及椎弓根钉棒系统相对位置与成人退变性脊柱侧凸(adult degenerative scoliosis,ADS)患者术后上位固定椎(upper instrumented vertebra,UIV)骨折的相关性以及UIV骨折的危险因素,并计算相关危险因素的准确阈值。方法对2016年1月至2018年1月,于我院接受治疗的164例ADS患者进行回顾性分析。获取相关影像学数据:冠状位脊柱侧凸Cobb’s角(coronal Cobb’s angle,CA),矢状位垂直轴(sagittal vertical axis,SVA),胸椎后凸角(thoracic kyphosis,TK),胸腰段后凸角(thoracolumbar kyphosis,TLK),冠状位垂直轴(coronal vertical axis,CVA),骶骨倾斜角(sacral slope,SS),腰椎前凸角(lumbar lordosis,LL),骨盆投射角(pelvis incidence,PI),骨盆倾斜角(pelvis tilt,PT),尖顶距(tip-apex distance,TAD),UIV前后距离(anteroposterior distance,APD),连接棒轮廓与椎体后壁之间的夹角(angle between the contour of the rod and the posterior wall of the vertebral body,ARV),椎弓根螺钉夹角(angle between pedicle screws,APS)。将患者分为UIV骨折组(F组)和无UIV骨折组(NF组)进行比较。采用多因素Logistic回归分析因变量与二分类自变量之间的相关性。使用受试者操作特征曲线(receiver operating characteristic curve,ROC)根据单变量Logistic回归分析的结果来确定影响因素的准确阈值。结果LL(P=0.011)、PI(P=0.047)为UIV骨折的术前危险因素;SS(P=0.020)为UIV骨折的术前保护危险因素。TAD为UIV骨折的术后危险因素(P<0.001);AVR为UIV骨折的术后保护因素(P<0.001)。UIV骨折较好的预测因素为术前LL(AUC=0.890,阈值=21.4)、术前PI(AUC=0.873,阈值=61.8)、术前SS(AUC=0.890,阈值=28.3)、TAD(AUC=0.660,阈值=31.5);预测效果较差的影响因素为ARV(AUC=0.332,阈值=3.0)。结论UIV骨折的发生是由于LL纠正不足,导致代偿性盆腔后倾和SVA较大的改变。椎弓根螺钉在椎体内部成角所形成的把持力在维持内固定系统的术后稳定方面,比椎弓根钉棒之间的相对角度有更重要的意义。

Objective To analyze the correlation between radiographic parameters,relative position of the pedicle screw-rod system and postoperative upper instrumented vertebra(UIV)fracture in postoperative adult degenerative scoliosis(ADS),to evaluate the risk factors for UIV fracture,and to calculate the accurate threshold of related risk factors.Methods This study retrospectively analyzed ADS patients who received treatment between January 2016 and January 2018.The radiographic parameters included Coronal Cobb’s Angle(CA),sagittal vertical axis(SVA),thoracic kyphosis(TK),thoracolumbar kyphosis(TLK),coronal vertical axis(CVA),sacral slope(SS),lumbar lordosis(LL),pelvis incidence(PI),pelvis tilt(PT),tip-apex distance(TAD),UIV anteroposterior distance(APD),angle between the contour of the rod and the posterior wall of the vertebral body(ARV),and angle between pedicle screws(APS).Patients were divided into UIV fracture group(F group)and non-UIV fracture group(NF group)for comparison.Multivariate logistic regression analysis was used to analyze the correlation between dependent variables and dichotomous independent variables.Receiver operating characteristic curve(ROC)was used to determine the exact threshold of risk factors based on the results of univariate logistic regression analysis.P<0.05 was considered to be statistically significant.Results LL(P=0.011)and PI(P=0.047)were the preoperative risk factors for UIV fracture.SS(P=0.020)was a preoperative protective factor for UIV fracture.TAD was a postoperative risk factor for UIV fracture(P<0.001).AVR was a protective factor for UIV fracture(P<0.001).Preoperative LL(AUC=0.890,threshold=21.4),preoperative PI(AUC=0.873,threshold=61.8),preoperative SS(AUC=0.890,threshold=28.3)and TAD(AUC=0.660,threshold=31.5)were good predictors of UIV fracture.ARV(AUC=0.332,threshold=3.0)was a risk factor of poor predictive effectiveness.Conclusions UIV fractures will occur when LL is inadequately corrected,resulting in compensatory pelvic retrograde and large changes in SVA.The holding force of pedicle screw angulated within the vertebral body is more important than the relative angle between pedicle screw rods in maintaining the postoperative stability of the internal fixation system.