Facet angle and its importance on joint violation in percutaneous pedicle screw fixation in lumbar vertebrae: A retrospective study

This is a retrospective study of case records. The aim of this study was to investigate the relationship between the facet angle (FA) at the pedicle level and facet joint violation (FJV) in percutaneous pedicle screw fixation (PPSF) in lumbar vertebrae. Current PPSF technique has a high facet violation rate than open surgery, and the relationship of FJV and FA has not been studied. Retrospective imaging analysis was conducted for 115 cases who underwent PPSF from December 2013 to November 2016 by the same group of surgeons using the same technique, in the spine surgery center of our hospital. The FA at the pedicle level was measured by computed tomography, and diagnosis and evaluation of FJV grade were performed postoperatively. The effect of the variant FA and lumbar segment (L1-L5) on FJV, and the correlation between FA and the FJV and FJV grade in PPSF were evaluated. A total of 476 percutaneous pedicle screws were included: 144 L1, 136 L2, 64 L3, 72 L4, and 60 L5 screws, with a total FJV rate of 30.46% (145/476). The FJV rate was 28.78% in upper lumbar group with 344 screws (99/344), and 34.85% in lower lumbar group with 132 screws (46/132). There was no significant difference between groups with regards to FJV rate, and age, sex, or BMI index. Evaluation of variant FA and lumbar segment on FJV rate indicated that FJV rate increased dramatically when FA >35 degree; however, FJV rate was not significantly related to the lumbar segment. There was a positive correlation between FA and FJV rate, as well as FA and FJV grade. There was a positive correlation between the increase of the FA at the pedicle level, and the FJV rate and FJV grade. The FJV risk increased remarkably when the FA was >35 degree.