Risk Factors And Clinical Outcomes Related To Superior Facet Joint Violation During Lumbar Percutaneous Pedicle Screw Insertion

Background:As a long-term complication of lumbar fusion,adjacent segment degeneration(ASD)has attracted more attention in clinical practice.The changes of load and range of motion of adjacent segment after spinal fusion can cause superior segment degeneration.Some patients may have clinical symptoms,of which the reoperation rate of symptomatic ASD within 10 years is 36.1%.Facet joint violation(FJV)has been confirmed to be a risk factor for ASD.Biomechanical studies have shown that the injury of pedicle screw to the superior adjacent facet joint(FJ)will increase the axial rotation angle,the pressure of the FJ and the pressure within the intervertebral disc,thus affecting the stability of adjacent segments.Compared with open TLIF,minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF)has been widely performed to reduce intraoperative blood loss,avoid paraspinal muscle and soft tissue injuries,and alleviate postoperative pain.However,due to its non-direct vision,percutaneous pedicle screw placement in MIS-TLIF may be more likely to interfere with FJ.Scholars have reported the effect of percutaneous screw placement on FJV for the first time.Their results show that the violation rate is still 31.5%(58/184)even if the screw insertion point is strictly selected during surgery.Subsequent literatures have reported different violation rates with different surgical methods and violation definition criteria.Avoidance of FJV has become an indispensable surgical target.At present,the analysis of risk factors for FJV mainly focuses on the general condition of patients,and the conclusions on age,gender and obesity are controversial.The anatomical structure of the FJ has individual specific characteristics.A cadaveric study has suggested that the hypertrophy of FJ may be a risk factor for high violation rate.However,no research has quantitatively measured the size of FJ,and studied its effect on FJV.Besides,the surgical details of percutaneous pedicle screw placement directly influence the FJV,and surgery-related factors should be comprehensively explored.To explore the incidence of facet joint violation(FJV)in minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF),and the risk factors of FJV were assessed from three aspects as follows:general condition,anatomical factors and surgical factors.Objective:To explore the incidence of facet joint violation(FJV)in minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF),and the risk factors of FJV were assessed from three aspects as follows;general condition,anatomical factors and surgical factors.The effects of FJV on clinical outcomes was also analysed.Method:91 cases of lumbar degenerative diseases treated with percutaneous pedicle screw insertion from 2012 to 2019 was retrospectively analysis,including 34 males and 57 females,with ages ranging from 23 to 73 years(mean of 51.05±11.81 years).The course of disease was 6-240 months,with an average of(50.6±65.6)months,and the average follow-up time was 50.23±93.15 months.53 cases of lumbar spinal stenosis,6 cases of lumbar disc herniation and 32 cases of lumbar spondylolisthesis(grade Ⅰ and Ⅱ)were enrolled.All patients underwent MIS-TLIF with percutaneous pedicle screw insertion.Three-dimensional lumbar CT reconstruction was carried pre-and postoperatively,and FJV and FJD was evaluated and graded by three dimensional plane of CT.Preoperative FJD was evaluated according to Weishaupt’s standard as follows:grade 0,normal;grade 1,mild degeneration;grade 2,moderate degeneration;grade 3,severe degeneration.Postoperative FJV was assessed according to Babu,and the degree of violation was classified into four grades:grade 0,screw was not in the facet and did not encroach upon the facet joint;grade 1,screw was in the lateral facet but did not enter the articular facet;grade 2,screw that penetrated the articular facet by<1 mm;grade 3,screw travelling within the articular surface of the facet.Evaluation was independently conducted by two experienced spine surgeons,and Kappa coefficient and intraclass correlation coefficient(ICC)were held to describe interobserver reliability.Patients report clinical outcomes were evaluated by visual analogue score(VAS)and Oswestry disability index(ODI).Chi-square test and binary logistic regression analysis were used to analyze the general factors related to FJV,including age,gender,BMI,surgical segment,preoperative diagnosis,screw location and FJD.Radiographic factors were measured on preoperative and postoperative CT and X-ray,including the anatomical characteristics of facet joint(axial,sagittal,coronal diameter of FJ,facet angle(FA),depth of lamina,lumbar lordosis angle(LLA),lumbar lordosis index(LLI)),the surgical factors(pedicle screw angle,cranial angle,screw-superior FJ distance,rod contouring,proximal rod length).Results:The kappa coefficient for interobserver agreement on FJD and FJV were substantial(k=0.677;k=0.784),and good interobserver reproducibility for radiographic parameters(ICC:0.687-0.893).The total violation rate of FJ was 34.07%(62/182),16.06%(27/182)above grade Ⅱ.35 with mild violation(grade 1),16 with moderate violation(grade 2)and 11 with severe violation(grade 3).When pedicle screw was placed at L5,the violation rate was 45.45%(30/66)and 21.21%(14/66)above grade Ⅱ.Chi-square test showed that patients with a BMI≥30 kg/m2 were more prone to violation(P=0.002).The most cephalad pedicle screws at L5 had a higher incidence of FJV compared with other superior segments(P=0.012).However,age,gender,FJD,and diagnosis were not correlated with violation.Binary logistic regression analysis showed that BMI≥30 kg/m2(OR 0.35,95%CI 0.20-0.72;P=0.003)and pedicle screw placement at L5(OR 0.45,95%CI 0.23-0.86;P=0.015)were independent risk factors for FJV.The results of anatomic factors showed that the FJ had a larger axial diameter(12.63±1.08 vs 12.11 ± 1.76,P=0.016),coronal diameter(12.39±1.46 vs 11.63±2.17,P=0.006),sagittal diameter(12.70± 1.31 vs 11.77±2.22,P=0.001)in the FJV group.The facet joint angle in the violation group was significantly larger than that in the non-violation group(47.18± 12.30 vs 31.68±6.45,P=0.000).When the axial,coronal and sagittal diameters of FJ were all≥12 mm or FA≥40°,the violation rate was significantly increased(P<0.05).No statistical difference in depth of lamina,LLA and LLI between two groups.According to surgical factors,the result showed that the FJV group had a smaller pedicle screw angle(14.86±5.45 vs 18.01 ±4.43,P=0.000)and screw-superior FJ distance(5.57± 1.24 vs 6.48± 1.17,P=0.000)compared with the non-FJV group(P<0.05),However,there was no statistical difference between the two groups in terms of cranial angle,rod contouring and proximal rod length.The results of receiver operating characteristic(ROC)showed that the facet joint angle(AUC:0.873,95%CI:0.811-0.935,P<0.001),pedicle screw angle(AUC:0.854,95%CI:0.789-0.919,P<0.001),and screw-superior FJ distance(AUC:0.912,95%CI:0.864-0.919,P<0.001)had larger AUC area.ROC analysis results of the facet joint diameters were as follows:Coronal diameter(AUC:0.700,95%CI:0.612-0.787,P=0.026);Sagittal diameter(AUC:0.712,95%CI:0.637-0.786,P=0.006);Axial diameter(AUC:0.728,95%CI:0.656-0.801,P=0.002).According to clinical outcomes,the VAS and ODI scores were significantly improved postoperatively in both groups.Compared with non-FJV group,the postoperative VAS back pain score(2.24 ±1.58 vs 1.67±1.15,P=0.001)and ODI score(13.44 ± 6.57 vs 11.06 ±4.38,P=0.017)in FJV group were poorer at 2-year follow-up.Conclusion:FJV has a negative effect on short term clinical outcomes in MIS-TLIF.BMI≥30 kg/m2,the cephalad pedicle screws at L5 as independent risk factors of FJV.FJV occured more often in a hypertrophic facet joint(axial,sagittal,coronal diameters≥12mm)or facet angle≥40°.The surgeon should evaluate the size and angle of facet joint before surgery,especially when inserting the pedicle screws at L5 segment.