Magnetic resonance imaging (MRI) data of 87 patients with suspected cervical posterior longitudinal ligament (PLL) rupture,who underwent cervical spine surgery in Luoyang Orthopedic Hospital from January 2015 to September 2017,were analyzed retrospectively.The criteria of MRI diagnosis for PLL rupture were the low signal image of the PLL on the posterior margin of the vertebral body,the discontinuity or continuous interruption,or the local highlighting signal on the T2 weighted image.According to intraoperative findings,the diagnostic accuracy of MRI for PLL rupture was examined.Among 87 patients,31 cases were diganosed as PLL rupture by preoperative MRI;and 38 cases were confirmed by intraoperative exploration,of whom 30 were diagnosed with MRI,and 8 were missed by MRI.The accuracy,sensitivity and specificity of MRI in the diagnosis of ruptured PLL were 0.90,0.79 and 0.98 respectively.MRI has a good diagnostic efficiency in PLL rupture,which can be used for preoperative investigation.

Objectives:To investigate and analyze the risk factors of screw loosening after single segment posterior lumbar interbody fusion(PLIF)with cortical bone trajectory(CBT)screw,and to establish and validate a visualized nomogram predictive model.Methods:A retrospective study was conducted on 102 patients un-dergone single-segment PLIF in our hospital from March 2020 to June 2023,and a total of 357 CBT screws were placed,averaged 3.5±0.3 per patient.The postoperative follow-up time was 2.0-35.0 months,with a me-dian of 22.5 months.On the basis of lumbar CT scans,screw loosening was defined as a continuous trans-parent area exceeding 1mm,surrounded with thin sclerotic areas.The patients were divided into loosening group of 45 cases and non-loosening group of 57 cases,with 117 screws loosening and 240 screws non-loosening.The demographic data[gender,age,body mass index(BMI),bone mineral density(BMD)],operative in-dicators(operative time,blood loss,lumbar fusion grade,Oswestry disability index),and radiological parameters[screw fixation to S1(FS1),screw trabecular Hounsfield unit(HU),screw sagittal angle(SA),coronary angle(CA),and cortical bone contact layer(CBCL)]were compared between groups.Lasso regression and multivariate logis-tic regression models were used to screen the optimal independent risk factors to screw loosening,and then a nomogram predictive model was constructed with R software.The internal predictive stability[consistency index(C-index)],prediction differentiation(sensitivity and specificity),prediction probability accuracy(degree of agree-ment),and net clinical benefit of the model was evaluated with Bootstrap method,receiver operating curve(ROC),calibration curve,and decision curve analysis(DCA).Results:The BMD in loosening group was signifi-cantly less than that in non-loosening group(P＜0.05),and there were no statistical differences in the other demographic data and surgical indexes between two groups(P＞0.05).Compared with non-loosening group,the FS1 percentage and CA in the loosening group significantly increased,while CBCL significantly decreased(P＜0.05).BMD(OR=0.44,95％CI=0.21-0.89,P＜0.001),FS1(OR=3.12,95％CI=2.03-4.54,P＜0.001),CA(OR=1.45,95％CI=1.12-2.03,P＜0.001),and CBCL(OR=0.67,95％CI=0.32-0.88,P＜0.001)were the independent risk fac-tors of screw loosening after single-segment PLIF.The total score of the model was 140 points.The bootstrap method calculated the C-index of 0.856(P=0.125),ROC showed area under curve(AUC)of 0.847(95％CI=0.801-0.912,P＜0.001).The calibration curve and DC A both showed good consistency in the model's predic-tive result and clinical net benefit ratio.Conclusions:The BMD,FS1,CA,and CBCL are the independent risk factors for screw loosening after single-segment PLIF with CBT screws,and the nomogram model con-structed has certain application values in early clinical screening of high-risk patients for screw loosening.