Facet Violation Research Articles

Safety evaluation of freehand lateral mass screw fixation in the subaxial cervical spine: evaluation of 1256 screws.

Prospective study. To evaluate the safety of the lateral mass screw (LMS) fixation. LMS fixation has been known to have risk of injury to vertebral artery, nerve root, or facet joints. A consecutive series of 178 patients undergoing planned LMS fixation were studied. Screw fixation was performed using the freehand technique. Entry point of screws was 2-mm medial from the center of the lateral mass. Planned divergent angle of the screw was 30º. Bicortical fixation was tried in all cases. After the surgery, all patients underwent 3-dimensional computed tomographic scan of the cervical spine. We checked the number of screws in each level, divergent angle of the screws, and violation of foramen transversarium (FT), intervertebral foramen, or facet joint by screws. A reliability test was performed. Total 1256 screws were fixed with 269 at C3, 318 at C4, 331 at C5, and 338 screws at C6. Mean divergent angle of the screws were 34.7º/33.1º at C3, 33.9 º/32.1º at C4, 34.7º/32.7º at C5, and 33.6º/30.7º at C6. Incidence of FT violation was 0.876%. FT violation was most common at C6 (6/11 violations). Mean divergent angle in cases of FT violation was 15.0º and was significantly smaller than that of safe cases. There was no injury to vertebral artery. There was no violation of intervertebral foramen. Incidence of facet violation was 1.433%. Seventeen facet violations were within fusion segment. Only 1 screw violated healthy facet. Facet violation was most common at C3 (12/18 violations). LMS fixation is a safe stabilizing technique with very low incidence of violation of FT, intervertebral foramen, and facet. There is a possibility of FT violation if the divergent angle was small. FT violation was most common at C6. Facet violation was most common at C3.

Use of anteroposterior view fluoroscopy for targeting percutaneous pedicle screws in cases of spinal deformity with axial rotation.

Over the past decade percutaneous pedicle screws have become popular for the minimally invasive treatment of spinal disorders. However, until the last 5 years the presence of a significant spinal deformity was regarded as a relative contraindication for percutaneous instrumentation. Recent advances in surgical technique and intraoperative technology have made percutaneous fixation in complex spinal pathologies more commonplace. The authors report their experience using a parsimonious method for uniplanar fluoroscopic targeting of pedicles in challenging cases. The authors performed a retrospective analysis of patients with adult spinal deformity who underwent percutaneous pedicle screw instrumentation from 2008 to 2013. Cases were included if a spiral slice postoperative CT scan was obtained. All cases had a minimum of 10° of axial rotation and typically had additional accompanying anatomical abnormalities. Screws were assessed for any pedicle violations as well as any impingement of the surrounding facet joints. A total of 410 pedicle screws were placed in 36 patients with an average 6.4 levels of instrumentation per patient. The mean age was 67 years (range 44-86 years) and there were 25 females. Of the 410 screws, 29 (7.1%) had some medial or lateral pedicle violation. Of these, 15 (3.7%) were Grade 1, 6 (1.4%) were Grade 2, and 8 (2.0%) were Grade 3 violations. Of the Grade 3 violations, 2 each were at the L-4, L-5, and S-1 levels, and 1 each was at the T-10 and L-1 levels. Two of the patients had symptoms and both underwent screw repositioning, one during the same admission and the other in a delayed fashion. Both were at the L-5 and S-1 levels with anatomically highly medialized pedicles. There were no motor deficits, and both removals were for numbness. Of the 72 screws at the proximal end of the construct, there were 6 facet violations (8.3%). Four (5.6%) of these were Grade 1, 1 (1.4%) was Grade 2, and 1 (1.4%) was Grade 3. The anteroposterior fluoroscopic technique can be effectively used by spinal surgeons to cannulate the pedicles in patients with rotational deformities. The complication rate in this challenging population is acceptable and is in accordance with the existing literature. However, caution should be used at L-5 and S-1 when the pedicle is narrow and highly medialized, rendering an indistinct medial wall on anteroposterior imaging.

Superior articulating facet violation: percutaneous versus open techniques

Recent studies have reported the incidence of superior facet joint violation using percutaneous techniques. These techniques have not been compared with the open midline approach. An increased incidence of superior facet violation may lead to adjacent-segment disease. In this paper, the authors' goal is to compare the rate of superior facet violation with the use of percutaneously placed pedicle screws versus midline approach open placement. Patients who underwent a single-level fusion using a percutaneous approach from L-1 to S-1 who had undergone CT scanning within 1 year after surgery were identified. A cohort who underwent open fusion matched by level of surgery was identified. All CT scans were reviewed by 3 fellowship-trained spine surgeons to determine the degree of facet violation. The final categorization for each screw was based on the most frequent reading among the 6 evaluations. The Fisher test was used to determine the association of facet violation with approach. There were 66 patients in each group. Patients in the Percutaneous group were younger (mean 42.5 years) than those in the Open group (mean 57.8 years, p = 0.000). There was no statistically significant difference in sex distribution, surgical levels fused, or time between surgery and CT scan between the groups. Thirty-six (13.6%) of 264 screws in the percutaneous and 16 (6%) of 263 screws in the Open group were in the facet joint (p = 0.005). Of these, 17 (12%) of the 132 proximal screws in the percutaneous and 7 (5%) of the 131 proximal screws in the Open group were in the facet joint (p = 0.052). The use of a percutaneous method to insert pedicle screws results in a statistically significantly higher incidence of facet joint violation, even if only proximal screws are considered. Further studies are needed to determine if this leads to a higher incidence of symptomatic adjacent-level disease.

Incidence of and risk factors for superior facet violation in minimally invasive versus open pedicle screw placement during transforaminal lumbar interbody fusion: a comparative analysis

A reported risk factor for adjacent-segment disease is injury to the superior facet joint from pedicle screw placement. Given that the facet joint is not typically visualized during percutaneous pedicle screw insertion, there is a concern for increased facet violation (FV) in minimally invasive fusion procedures. The purpose of this study was to analyze and compare the incidence of FV among patients undergoing minimally invasive transforaminal lumbar interbody fusion (MITLIF) and open transforaminal lumbar interbody fusion (TLIF). The impact of O-arm navigation compared with traditional fluoroscopy on FV in MITLIF is also assessed, as are risk factors for FV. The authors identified a consecutive population of patients who underwent MITLIF with percutaneous pedicle screw placement, as well as a matched cohort of patients who underwent open TLIF. Postoperative CT imaging was assessed to determine intraarticular FV due to pedicle screw placement. Patients were stratified into minimally invasive and open TLIF groups. Within the MITLIF group, the authors performed a subanalysis of image guidance methods used in cases of FV. Two-tailed Student t-test, ANOVA, chi-square testing, and logistic regression were used for statistical analysis. A total of 282 patients were identified, with a total of 564 superior pedicle screw placements. The MITLIF group consisted of 142 patients with 284 screw insertions. The open TLIF group consisted of 140 patients with 280 screw insertions. Overall, 21 (7.4%) of 282 patients experienced FV. A total of 21 screws violated a facet joint for a screw-based FV rate of 3.7% (21 of 564 screws). There were no significant differences between the MITLIF and open TLIF groups in the percentage of patients with FV (6.3% vs 8.6%) and or the percentage of screws with FV (3.2% vs 4.3%) (p = 0.475 and p = 0.484, respectively). Further stratifying the MI group into O-arm navigation and fluoroscopic guidance subgroups, the patient-based rates of FV were 10.8% (4 of 37 patients) and 4.8% (5 of 105 patients), respectively, and the screw-based rates of FV were 5.4% (4 of 74 screws) and 2.4% (5 of 210 screws), respectively. There was no significant difference between the subgroups with respect to patient-based or screw-based FV rates (p = 0.375 and p = 0.442, respectively). The O-arm group had a significantly higher body mass index (BMI) (p = 0.021). BMI greater than 29.9 was independently associated with higher FV (OR 2.36, 95% CI 1.65-8.53, p = 0.039). The findings suggest that minimally invasive pedicle screw placement is not associated with higher rates of FV. Overall violation rates were similar in MITLIF and open TLIF. Higher BMI, however, was a risk factor for increased FV. The use of O-arm fluoroscopy with computer-assisted guidance did not significantly decrease the rate of FV.

Comparison of Cranial Facet Joint Violation Rates Between Open and Percutaneous Pedicle Screw Placement Using Intraoperative 3-D CT (O-arm) Computer Navigation

Retrospective study comparing cranial facet joint violation rates of open and percutaneous pedicle screws inserted using 3-dimensional image-guidance. To determine the rate of cranial facet joint violation in intraoperative computed tomography (CT) image-guided lumbar pedicle screw instrumentation and compare facet joint violation rates between CT image-guided open and percutaneous techniques. Facet joint violation by pedicle screws can potentially result in a higher rate of adjacent segment degeneration. Reported cranial facet joint violation rates range from 7% to 100%. Intraoperative image-guidance, which has enhanced pedicle screw placement accuracy, may aid in avoiding impingement of the cranial facet joints. We reviewed 188 cases of 3-dimensional image-guided lumbar pedicle screw instrumentation from November 2006 to December 2011. The cranial screws of each construct were graded by 3 reviewers according to the Seo classification (0 = no impingement; 1 = screw head in contact/suspected to be in contact with joint; 2 = screw clearly invaded the joint) on intraoperative axial CT images. If there was a difference in evaluation, a consensus was reached to arrive at a single grade. The χ2 test was used to determine significance between the open and percutaneous group (α = 0.05). A total of 370 screws (245 open, 125 percutaneous) were graded. Overall facet joint violation rate was 18.9% (grade 1 = 16.2%, grade 2 = 2.7%). Open technique (grade 1 = 22.4%, grade 2 = 4.1%) had a significantly higher violation rate than percutaneous technique (grade 1 = 4%, grade 2 = 0%) (P < 0.0001). There is a trend of an increasing likelihood of facet joint violation from L1 to L5. The use of intraoperative CT image-guidance in lumbar pedicle screw placement resulted in a facet joint violation rate at the lower end of the reported range in literature. The percutaneous technique has a significantly lower facet violation rate than the open technique. 4.

The Biomechanical Effect of Pedicle Screwsʼ Insertion Angle and Position on the Superior Adjacent Segment in 1 Segment Lumbar Fusion

A finite element analysis. To investigate the association between the position of an inserted pedicle screw and the corresponding facet contact force or intradiscal pressure. Although superior facet joint violation by pedicle screws is not an uncommon occurrence in instrumented lumbar fusion surgery, its actual biomechanical significance is not well understood. Furthermore, the association between the position of the pedicle screw and the stress on the corresponding disc/facet joint has yet to be investigated. According to the positions of pedicle screws in L4 of the L4-L5 lumbar fusion, 4 L4-L5 fusion models were simulated. These models included the violation of both L3-L4 superior facet joints by pedicle screws (facet joint violation [FV] model), the nonencroachment of both L3-L4 superior facet joints by pedicle screws (facet joint preservation [FP] model), and the removal state of pedicle screws in the FV model (removal of violated pedicle screws [rFV] model). The facet joint contact [FC] model represented the scenario in which the pedicle screws did not encroach upon either facet joint but were inserted close to the L3-L4 facet joint surface. Moreover, the uninstrumented fusion [UF] model represented the uninstrumented L4-L5 fusion. In each scenario, the intradiscal pressures and facet contact forces at the L2-L3 and L3-L4 segments were analyzed under extension and torsion moments. The FV model yielded the greatest increases in facet contact force and intradiscal pressure at the L3-L4 segment under extension and torsion moments. Following the FV model, the increases in intradiscal pressure and facet contact force were the second highest in the FC model followed by the FP model. Furthermore, the rFV model represented prominent reductions of previously increased facet contact force and intradiscal pressure at the L3-L4 segment. In models of 1-segment lumbar fusion surgery, the positions of pedicle screws were closely linked with corresponding disc stresses and facet contact forces. However, even in cases of facet violation by pedicle screws, removal of the pedicle screw after fusion completion can reduce facet contract forces and disc stresses under both extension and torsional moments.

Comparison of Superior-Level Facet Joint Violations During Open and Percutaneous Pedicle Screw Placement

Superior-level facet joint violation by pedicle screws may result in increased stress to the level above the instrumentation and may contribute to adjacent segment disease. Previous studies have evaluated facet joint violations in open or percutaneous screw cases, but there are no reports describing a direct institutional comparison. To compare the incidence of superior-level facet violation for open vs percutaneous pedicle screws and to evaluate patient and surgical factors that affect this outcome. We reviewed 279 consecutive patients who underwent an index instrumented lumbar fusion from 2007 to 2011 for degenerative spine disease with stenosis with or without spondylolisthesis. We used a computed tomography grading system that represents progressively increasing grades of facet joint violation. Patient and surgical factors were evaluated to determine their impact on facet violation. Our cohort consisted of 126 open and 153 percutaneous cases. Percutaneous procedures had a higher overall violation grade (P = .02) and a greater incidence of high-grade violations (P = .006) compared with open procedures. Bivariate analysis showed significantly greater violations in percutaneous cases for age < 65 years, obesity, pedicle screws at L4, and 1- and 2-level surgeries. Multivariate analysis showed the percutaneous approach and depth of the spine to be independent risk factors for high-grade violations. This study demonstrates greater facet violations for percutaneously placed pedicle screws compared with open screws.

Facet Violation With the Placement of Percutaneous Pedicle Screws

Facet Violation With the Placement of Percutaneous Pedicle Screws

Facet Violation With the Placement of Percutaneous Pedicle Screws

Independent review and classification of therapeutic procedures performed on cadavers by surgeons blinded to purpose of study. The objective of this study is to determine the rate of facet violation with the placement of percutaneous pedicle screws. Improvements in percutaneous instrumentation and fluoroscopic imaging have led to a resurgence of percutaneous pedicle screw insertion in lumbar spine surgery in an attempt to minimize many of the complications associated with open techniques of pedicle screw placement. Rates of pedicle breech and neurologic injury resulting from percutaneous insertion are reportedly similar to those of open techniques. Postoperative pain because of impingement and instability is believed to result from violation of the facet capsule or facet joint. To the authors' knowledge, however, the rate of facet injury associated with the placement of percutaneous pedicle screws is unreported in the literature. Percutaneous pedicle screw placement was performed on 4 cadaveric specimens by 4 certified orthopedic surgeons who had clinical experience in the procedure and who were blinded to the study's purpose. The surgeons were instructed to place pedicle screws from L1-S1 using their preferred clinical techniques and a 5.5-mm screw system with which they were all familiar. All surgeons utilized 1 OEC C-arm for fluoroscopic imaging. After insertion, 2 independent spine surgeons each reviewed and classified the placement of all facet screws. A total of 48 screws were inserted and classified. The placement of 28 screws (58%) resulted in violation of facet articulation, with 8 of these screws being intra-articular. Interobserver reliability of the classification system was 100%. Percutaneous pedicle screw placement may result in a high rate of facet violation. Facet injury can be reliability classified and therefore, perhaps, easily prevented.

Superior segment facet joint violation and cortical violation after minimally invasive pedicle screw placement

Background context Minimally invasive approaches to the lumbar spine allow for pedicle screw placement through a muscle-splitting paraspinal approach. These techniques are highly dependent on fluoroscopy and do not allow for direct visualization of anatomic landmarks. The effect of this on the accuracy of pedicle screw placement is not well described. The purpose of this study was to evaluate the rate of violation of the superior segment facet joint and rates of cortical violation after minimally invasive pedicle screw placement. Purpose To evaluate the rate of cortical violation and involvement of the superior segment facet after minimally invasive pedicle screw placement. Study design/setting Retrospective chart review. Patient sample Patients who underwent minimally invasive pedicle screw placement by a single surgeon between January 2004 and July 2009. Outcome measures Violation of the superior segment facet joint or cortical violation identified on computed tomography (CT). Methods This study consisted of a consecutive series of adult patients undergoing minimally invasive pedicle screw placement by a single surgeon for degenerative lumbar spinal conditions. Routine postoperative CT was obtained and evaluated for involvement of the superior segment facet joint and for cortical violation. Results Sixty-one consecutive patients (282 pedicle screws) met the study criteria and were included in the study, including 42 single-level fusions and 19 two-level fusions. Seven cortical breaches were identified for a rate of 2.48%. Seven patients had involvement of the superior-level facet for an incidence of 11.48%. One patient required revision for a malpositioned pedicle screw. Conclusions This study revealed a low rate of superior segment facet violation and cortical violation after minimally invasive pedicle screw placement. This rate of superior-level facet involvement is significantly lower than previously reported after open procedures. The rate of cortical violation is similar to previous reports in the literature with a low revision rate.

Does Superior-Segment Facet Violation or Laminectomy Destabilize the Adjacent Level in Lumbar Transpedicular Fixation?

This is an in vitro biomechanical study. The current investigation was performed to evaluate adjacent level kinematic change following unilateral and bilateral facet violation and laminectomy following 1-, 2-, and 3-level reconstruction. The incidence of superior-segment facet violation with lumbar transpedicular fixation has been reported as high as 35%; however, its contribution to biomechanical instability at the supradjacent level is unknown. In addition, superior-segment laminectomy has been implicated as a risk factor for the development of adjacent level disease. The authors assess the acute biomechanical effects of proximal facet violation and subsequent laminectomy in an instrumented posterior fusion model in 10 cadaveric specimens. Biomechanical testing was performed on 10 human cadaveric spines under axial rotation (AR), flexion-extension (FE), and lateral bending (LB) loading. After intact analysis, pedicle screws were inserted from L5-S1 and testing repeated with: (1) preserved L4-L5 facets, (2) unilateral facet breach, (3) bilateral breach, and (4) L5 laminectomy. Following biomechanical analysis, instrumentation was extended to L4, then L3 and biomechanical testing repeated. Full range of motion (ROM) at the proximal adjacent levels were recorded and normalized to intact (100%). Supradjacent level ROM was increased for all groups under all loading methods relative to intact (P < 0.05). However, AR testing revealed progressive instability at the adjacent level in groups 3 and 4, relative to group 1, following 1-, 2- and 3-level fixation (P < 0.05). During FE, supradjacent level ROM was significantly increased for group 4 specimens compared with group 1 after L5-S1 fixation (P < 0.05), and was greater than all other groups for L3-S1 constructs (P < 0.05). Interestingly, under lateral bending, facet joint destabilization did not change adjacent segment ROM. There were significant changes in proximal level ROM immediately after posterior stabilization. However, an additional increase in supradjacent segment ROM was recorded during AR after bilateral facet breach.Subsequent complete laminectomy at the uppermostfixation level further destabilized the supradjacent segment in FE and AR. Therefore, meticulous preservation of the cephalad-most segment facet joints-is paramount to ensure stability.

Does Proximal Facet Violation with Intrapedicular Fixation Destabilize the Adjacent Level? An In Vitro Human Cadaveric Assessment

Does Proximal Facet Violation with Intrapedicular Fixation Destabilize the Adjacent Level? An In Vitro Human Cadaveric Assessment

6:00 192. Outcomes following superior segment facet joint violation in pedicle instrumentation of the lumbar spine

BACKGROUND CONTEXT: Superior segment facet violation following transpedicular screw fixation in the lumbar spine have been reported in approximately 24–30% of patients (15–20% of screws) for the midline and Wiltse approaches. It is not clear whether facet joint violations are associated with adverse clinical outcomes of surgery.

Complications of posterior cervical plating.

This retrospective clinical study evaluates complications occurring during or immediately after surgery of posterior cervical plating. The present study quantifies risks associated with posterior cervical plating using lateral mass screw fixation. The observed clinical complications are compared with theoretical risks previously studied in cadavers. Unanticipated complications are identified. There are many reports that describe posterior cervical plating and attempt to describe the indications for using this type of fixation, but few studies have discussed the clinical complications incurred by application of these plates and screws. Seventy-eight consecutive patients whose treatment included posterior cervical lateral mass plating were independently reviewed to identify associated complications. The average patient age was 52.9 years, and the average follow-up period was 2 years (range, 10-47 months). Multiple indications for surgery were present, but complex reconstructive procedures were required in 70.5% of cases. Complication rates were calculated as either a percentage of the number of screws inserted or as a percentage of the number of cases performed or both. Six hundred fifty-four screws were inserted--an average of 8.4 screws per patient. Complication rates as a function of the number of screws inserted included nerve root injury, 0.6%; facet violations, 0.2%; vertebral artery injury, 0%; broken screw, 0.3%; screw avulsion, 0.2%; and screw loosening 1.1%. Complications as a percentage of the number of cases performed included spinal cord injury, 2.6%; iatrogenic foraminal stenosis, 2.6%; broken plate, 1.3%; lost reduction, 2.6%; adjacent segment degeneration, 3.8%; infection, 1.3%; and pseudoarthrosis, 1.4%. Cadaveric work has predicted certain anatomic complication rates associated with lateral mass screw insertion. This study finds the risk of lateral mass screw insertion to be considerably less than predicted in vitro. The present study reports other complications that were not predicted in laboratory studies.