P20. Predisposing risk factors of the facet joint violation in the lumbar spinal fusion during the instrumentation of minimal invasive spinal surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> Trending of minimal invasive surgery is increased and adjacent segmental degeneration is the one of the complications sequentially from the procedures which the facet joint injury is one of the causes. The patients who have ASD have vary symptoms such as back pain, neurological compression and instability and some of them required the second or third operation. The facet joint violation can occur during the instrumentation which the surgeons had known the facet joint indirectly visualization. Risk factors of the facet joint violation have the many considerations such as the patient characteristics, facet anatomy, surgical techniques and radiographic assisted. <h3>PURPOSE</h3> Identify the risk factors which have affected the facet joint violation during the minimal invasive spinal surgery. <h3>STUDY DESIGN/SETTING</h3> Retrospective study which is an analysis of 119 patients who have had the minimal invasive spinal surgery from June 2018 to December 2019. <h3>PATIENT SAMPLE</h3> A total of 119 patients who have had the minimal invasive lumbar spinal surgery with percutaneous pedicular screw placed from June 2018 to December 2019. All patients had the CT and MRI scan postoperatively within 6 months after the operation will include to our study. <h3>OUTCOME MEASURES</h3> Facet joint violation at the uppermost level was examined by the CT scan in all dimensions. The facet joint violation defined as the instrument was breeched into the facet joint. We classified these findings as in the facet violation group. The none violation was classified into non-facet violation group. Radiographic parameters (Facet diameter, facet angle, pedicle angle, screw-facet angle, screw-endplate angle and distance between head of screws and facet) were measured. BMI, age, diagnosis and navigation-assisted were included. Risk factor were analyzed and determined which factor have had an effect to the facet joint violation and scoring system for the risk factor was calculated. <h3>METHODS</h3> This study is an analysis of 119 patients who have had the minimal invasive spinal surgery from June 2018 to December 2019. Facet joint violation at the uppermost level was examined by the CT scan in all dimensions. Radiographic parameters (Facet diameter, facet angle, pedicle angle, screw-facet angle, screw-endplate angle and distance between head of screws and facet) were measured. BMI, age, diagnosis and navigation-assisted were included. Risk factor were analyzed and determined which factor have had an effect to the facet joint violation and scoring system for the risk factor was calculated. <h3>RESULTS</h3> A total of 119 patients, 36 males and 83 females, patients mean age was 63 years old, diagnosis was 38 patients had SCS, 54 patients had spondylolisthesis, 17 had HNP, 4 had degenerative scoliosis and 6 had degenerative disc disease. Facet violation was determined 1 patient at L1, 3 patients at L2, 20 patients at L3, 79 patients at L4 and 16 patients at L5. Facet joint violation occurred in 13/119(10.9%) and 15/238(6.3%) joints. No facet joint violation occurred in 60 patients who navigation-assisted was used, versus 15/178(8.4%) joints where there was no navigation(P=0.01). We found an increasing proportion of violations as the lumbar level increased: no violations occurred in 8 patients with lumbar at L1 or L2, 1/40(2.5%), 7/158(4.4%) and 7/32 (21.9%) of violations occurred at L3, L4 and L5, respectively (P=0.01). Although it was not statistically significant, the percentage of violations was higher in patients with scoliosis (12.5%) and DDD (16.7%). Diameter of facet in axial cut, facet angle, screw facet angle and distance between head of screw and facet was statistically significant to determine increasing rate of facet joint violations after multivariable analysis was done (AROC=0.9486, P≤0.05). <h3>CONCLUSIONS</h3> Increasing of the facet diameter in axial plane, facet angle, screw facet angle and distance between dome of screw and facet are one of the risk factor of facet joint violation. Surgeon can avoid the violation when the radiographic consideration was done. Careful screw placement and make the good entry points for instrumentation will decrease rate of facet violation. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.