Risk factors of superior facet joint violation in minimally invasive transforaminal lumbar interbody fusion

English Keywords:Facet joint violation  Risk factors  Hypertrophic facet joint  Facet angle

English Abstract:

  【Abstract】 Objectives: To explore the incidence of superior facet joint violation(FJV) during lumbar percutaneous pedicle screw insertion in minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF) surgery, and the possible risk factors of FJV. Methods: A retrospective study was performed on 91 patients with lumbar degenerative diseases treated with MIS-TLIF from 2012 to 2018, including 34 males and 57 females with an average age of 51.1±11.8 years(ranging from 23 to 73 years). All patients underwent three-dimensional CT reconstruction of lumbar spine, and FJV was evaluated and graded on axial, sagittal and coronal plane of CT: grade 0, no encroachment, screw not in the facets or the articular surface; grade 1, mild encroachment, screw was in the surperior facet but did not enter the articular surface; grade 2, moderate encroachment, screw penetrated the articular surface≤1mm; grade 3, severe encroachment,screw entered the articular surface of the facet. Possible risk factors were collected and analyzed, including general condition of patients, the anatomical characteristics of facet joint(FJ)[axial, sagittal, coronal diameter of FJ, facet angle(FA), lumbar lordosis angle(LLA), lumbar lordosis index(LLI), depth of lamina], and the surgical factors(pedicle screw angle, screw-superior FJ distance, cranial angle, proximal rod length, rod contouring). Results: A total of 62 pedicle screws resulted in FJV during percutaneous pedicle screw placement in MIS-TLIF in which, 35 with mild violation, 27 with moderate and severe violation. The Logistic regression analysis revealed that, BMI≥30kg/m2, pedicle screw placement at L5 were independent risk factors of FJV. However, age, gender, preoperative diagnosis and FJD were not correlated with FJV. Anatomical factors showed that the incidence of FJV significantly increased when axial, sagittal, coronal diameter of facet joint were all ≥12mm(P＜0.05) or either the FA≥40°(P<0.05). There was no statistical difference in LLA, LLI and depth of lamina between the FJV group and the non-FJV group(P＞0.05). The FJV group had a smaller pedicle screw angle and screw-superior FJ distance than the non-FJV group(P＞0.05), while there was no statistical difference between the groups in cranial angle, proximal rod length and rod contouring(P＞0.05). Conclusions: BMI≥30kg/m2, pedicle screw placement at L5 were independent risk factors of FJV. FJV were more likely to occur in patients with a hypertrophic facet joint (axial, sagittal, coronal diameters ≥12mm) or acoronally oriented facet joint(facet angle ≥40°).