Facet violation with the placement of percutaneous pedicle screws

Biomechanical Comparison of Unilateral and Bilateral Pedicle Screw Fixation after Multilevel Lumbar Lateral Interbody Fusion

STUDY DESIGN

Human Cadaveric Biomechanical Study.

OBJECTIVES

Lumbar Lateral Interbody Fusion (LLIF) utilizing a wide cage has been reported as having favorable biomechanical characteristics. We examine the biomechanical stability of unilateral pedicle screw and rod fixation after multilevel LLIF utilizing 26 mm wide cages compared to bilateral fixation.

METHODS

Eight human cadaveric specimens of L1-L5 were included. Specimens were attached to a universal testing machine (MTS 30/G). Three-dimensional specimen range of motion (ROM) was recorded using an optical motion-tracking device. Specimens were tested in 3 conditions: 1) intact, 2) L1-L5 LLIF (4 levels) with unilateral rod, 3) L1-L5 LLIF with bilateral rods.

RESULTS

From the intact condition, LLIF with unilateral rod decreased flexion-extension by 77%, lateral bending by 53%, and axial rotation by 26%. In LLIF with bilateral rods, flexion-extension decreased by 83%, lateral bending by 64%, and axial rotation by 34%. Comparing unilateral and bilateral fixation, LLIF with bilateral rods reduced ROM by a further 23% in flexion-extension, 25% in lateral bending, and 11% in axial rotation. The difference was statistically significant in flexion-extension and lateral bending (P < .005).

CONCLUSIONS

Considerable decreases in ROM were observed after multilevel (4-level) LLIF utilizing 26 mm cages supplemented with both unilateral and bilateral pedicle screws and rods. The addition of bilateral fixation provides a 10-25% additional decrease in ROM. These results can inform surgeons of the incremental biomechanical benefit when considering unilateral or bilateral posterior fixation after multilevel LLIF.

Risk Factors for Residual Back Pain After PVP Treatment for osteoporotic Thoracolumbar Compression Fractures: A Retrospective Cohort Study

OBJECTIVES

To explore the risk factors of residual back pain after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compression fracture (OVCF).

METHODS

We retrospectively reviewed the records of 675 patients with OVCF treated with PVP from January 2015 to January 2020. Postoperative back pain intensity was assessed by the VAS score. Residual back pain was defined as the presence of postoperative moderate-severe pain (average VAS score≥4), and the variables included patient characteristics, baseline symptoms, imaging data and operation-related factors. Risk factors were identified with univariate and multivariate logistic regression analysis.

RESULTS

Residual back pain occurred in 46 of the 675 patients included in the study, with an incidence rate of 6.8%. Multivariate logistic regression analysis showed that low Pre-BMD (OR = 3.576, P = 0.041), multiple vertebral fractures (OR = 2.795, P = 0.026), posterior fascia injury (OR = 4.083, P = 0.032), cement diffusion volume rate <0.2 (OR = 3.507, P = 0.013), facet joint violation (OR = 11.204, P < 0.001), and depression (OR = 3.562, P = 0.035) were positively correlated with residual back pain after PVP.

CONCLUSIONS

Low pre-BMD (pre-bone mineral density), multiple vertebral fractures, posterior fascia injury, cement diffusion volume rate <0.2, facet joint violation and depression were the independent risk factors of residual back pain after PVP.

Clinical Validity of 3 Different Grading Systems for Facet Joint Violation: A Retrospective Study and In-Depth Review

STUDY DESIGN

Retrospective.

OBJECTIVES

To study the violation rate of 3 different types of facet joint violation (FJV) grading systems (Babu, Shah, and Park), and to evaluate the accuracy, reliability, and association with clinical outcomes of the above 3 grading systems.

METHODS

152 patients of lumbar spinal stenosis treated with percutaneous pedicle screw placement were enrolled in our study. FJV was evaluated on 3-dimensional lumbar CT reconstruction. Three types of grading systems were used to evaluate FJV: Babu's system (grading by the severity of violation), Shah's system (grading by side of violation), and modified Park's system (grading by different components to cause violation). The violation rate and observer consistency of the 3 grading systems were analyzed. Clinical outcomes were evaluated by visual analog score (VAS), Oswestry disability index (ODI) score.

RESULTS

Kappa coefficients of interobserver consistency on Babu, Shah, and Park grading systems were 0.726,0.849,0.692, respectively. The violation rate of Babu, Shah, and Park grading systems were comparable, which were 34.54%, 32.57%, 33.55%, respectively. In all 3 grading systems, the postoperative VAS low-back pain and ODI scores in non-FJV groups were lower than those in FJV groups (P < .05), and there were no significant differences between 2 groups in VAS leg pain(P >.05).

CONCLUSIONS

Babu, Shah and modified Park grading system are reliable grading systems, and it reported comparable violation rate. The self-reported clinical outcomes of patients with FJV were worse at 2-year follow-up. For clinical application, it is recommended to use 2 or even 3 different grading systems together to evaluate the FJV.

Facet joint violation after open and percutaneous posterior instrumentation: a comparative study

PURPOSE

Posterior instrumentation is the state-of-the-art surgical treatment for fractures of the thoracic and lumbar spine. Options for pedicle screw placement comprise open or minimally invasive techniques. Open instrumentation causes large approach related muscle detachment, which minimally invasive techniques aim to reduce. However, concerns of accurate pedicle screw placement are still a matter of debate. Beside neurological complications due to pedicle screw malplacement, also affection of the facet joints and thus motion dependent pain is known as a complication. The aim of this study was to assess accuracy of pedicle screw placement concerning facet joint violation (FJV) after open- and minimally invasive posterior instrumentation.

METHODS

A retrospective data analysis of postoperative computer tomographic scans of 219 patients (1124 pedicle screws) was conducted. A total of 116 patients underwent open screw insertion (634 screws) and 103 patients underwent minimally invasive, percutaneous screw insertion (490 screws).

RESULTS

In the lumbar spine (segments L3, L4, L5), there were significantly more and higher grade (open = 0.55 vs. percutaneous = 1.2; p = 0.001) FJV's after percutaneously compared to openly inserted screws. In the thoracic spine, no significant difference concerning rate and grade of FJV was found (p > 0.56).

CONCLUSION

FJV is more likely to occur in percutaneously placed pedicle screws. Additionally, higher grade FJV's occur after percutaneous instrumentation. However, in the thoracic spine we didn't find a significant difference between open and percutaneous technique. Our results suggest a precise consideration concerning surgical technique according to the fractured vertebrae in the light of the individual anatomic structures in the preop CT.

Adjacent Segment Impingement: A New Type of Adjacent Segment Disease?: A Report of 3 Cases

CASE

We present 3 cases in which spinal rods extending beyond the intended level of fusion caused injury to adjacent structures, which we term "adjacent segment impingement." All cases presented as back pain with no neurological symptoms, with a minimum 6 years of follow-up from the initial procedure. Treatment consisted of extending the fusion to include the affected adjacent segment.

CONCLUSION

We recommend surgeons check to ensure spinal rods are not abutting adjacent level structures at the time of the initial implant while considering that adjacent levels may move closer to the rod during spine extension or twisting.

Incidence and risk factors associated with superior-segmented facet joint violation during minimal invasive lumbar interbody fusion

BACKGROUND CONTEXT

The trend of minimally invasive lumbar interbody fusion is increasing, and adjacent segmental degeneration (ASD) is one of the complications of the procedures in which facet joint violation (FJV) is a cause. FJVs can occur during percutaneous instrumentation. This study aimed to identify the risk factors that affect FJV during minimally invasive lumbar interbody fusion.

PURPOSE

To identify the risk factors for FJVs and the factors that have a strong impact on the violation.

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

Patients who underwent minimally invasive lumbar interbody fusion with percutaneous screw fixation between June 2018 and December 2019.

OUTCOME MEASURES

Prevalence of the FJV was reviewed by CT scans which obtained within 6 months after surgery, and the axial, coronal, and sagittal cuts of the scans were evaluated. The FJV was defined as the screw being visible in the facet joint in at least one plane of the CT scan. Radiographic parameters were measured using CT scans including diameters of the facet joints in the axial, coronal, and sagittal planes defined by the facet diameter. The facet angle (FA), the pedicle angle (PA), the screw-facet angle (SFA), the screw-endplate angle (SEA), and the superior margin of the facet joint in the sagittal plane (SD) differed from the head of the screw. At Last, the depth of back muscle was measured in the axial cut of the MRI.

METHODS

This study analyzed 119 patients who underwent minimally invasive lumbar interbody fusion between June 2018 and December 2019. Facet joint violation at the uppermost level was examined using CT in all dimensions. Radiographic parameters (facet diameter, facet angle, pedicle angle, screw-facet angle, screw-endplate angle, and distance between the head of the screws and the facet) were measured. BMI, age, diagnosis, and navigation assistance were included in the study. Risk factors were analyzed to determine which factors had an effect on FJV, and the cut-off was calculated for each parameter.

RESULTS

This study included 119 patients, with a mean age of 63 years. FJV occurred in 13/119 (10.9%) patients and 15/238 (6.3%) joints, respectively. No FJV occurred in 120 joints operated with navigation-assistance and 15/178 (8.4%) joints operated without navigation (p=.01). We found an increasing proportion of violations at more caudal levels: no violations occurred in eight patients with lumbar at L1 or L2, and 1/40 (2.5%), 7/158 (4.4%), and 7/32 (21.9%) of violations occurred at L3, L4, and L5, respectively (p=.01). The diameter of the facet in the axial cut, facet angle, screw facet angle, and distance between the head of the screw and facet were statistically significant in determining the increasing rate of FJV after multivariate analysis was performed (AROC=0.9486, p≤.05). The cutoff point for each radiographic parameter were diameter of facet in the axial ≥17.5 mm, diameter of facet in coronal plane ≥19.5 mm, facet angle ≥41.5^o, screw-facet angle ≥39^o, and distance between facet and the screw ≥-2.6 mm. The estimated probability of FJV was 96.9% when every parameter was greater than the cut-off point.

CONCLUSIONS

An increase in the facet diameter in the axial plane, coronal plane, facet angle, screw facet angle, and the distance between the dome of the screw and facet are risk factors for FJV. Surgeons can avoid violations when radiographic considerations are done. Careful screw placement and good entry points for instrumentation may decrease the rate of facet violation.

Safety and risk factors of TINAVI robot-assisted percutaneous pedicle screw placement in spinal surgery

Objective

To determine the rates and risk factors of pedicle screw placement accuracy and the proximal facet joint violation (FJV) using TINAVI robot-assisted technique.

Methods

Patients with thoracolumbar fractures or degenerative diseases were retrospectively recruited from June 2018 and June 2020. The pedicle penetration and proximal FJV were compared in different instrumental levels to identify the safe and risk segments during insertion. Moreover, the factors were also assessed using univariate and multivariate analyses.

Results

A total of 72 patients with 332 pedicle screws were included in the current study. The optimal and clinically acceptable screw positions were 85.8% and 93.4%. Of the 332 screws concerning the intra-pedicular accuracy, 285 screws (85.8%) were evaluated as Grade A according to the Gertzbein and Robbins scale, with the remaining 25 (7.6%), 10 (3.0%), 6 (1.8%), and 6 screws (1.8%) as Grades B, C, D, and E. Moreover, in terms of the proximal FJV, 255 screws (76.8%) screws were assessed as Grade 0 according to the Babu scale, with the remaining 34 (10.3%), 22 (6.6%), and 21 screws (6.3%) as Grades 1, 2, and 3. Furthermore, the univariate analysis showed significantly higher rate of penetration for patients with age < 61 years old, sex of female, thoracolumbar insertion, shorter distance from skin to insertion point, and smaller facet angle. Meanwhile, the patients with the sex of female, BMI < 25.9, grade I spondylolisthesis, lumbosacral insertion, longer distance from skin to insertion point, and larger facet angle had a significantly higher rate of proximal FJV. The outcomes of multivariate analyses showed that sex of male (adjusted OR 0.320, 95% CI 0.140–0.732; p = 0.007), facet angle ≥ 45° (adjusted OR 0.266, 95% CI 0.090–0.786; p = 0.017), distance from skin to insertion point ≥ 4.5 cm (adjusted OR 0.342, 95% CI 0.134–0.868; p = 0.024), and lumbosacral instrumentation (adjusted OR 0.227, 95% CI 0.091–0.566; p = 0.001) were independently associated with intra-pedicular accuracy; the L5 insertion (adjusted OR 2.020, 95% CI 1.084–3.766; p = 0.027) and facet angle ≥ 45° (adjusted OR 1.839, 95% CI 1.026–3.298; p = 0.041) were independently associated with the proximal FJV.

Conclusion

TINAVI robot-assisted technique was associated with a high rate of pedicle screw placement and a low rate of proximal FJV. This new technique showed a safe and precise performance for pedicle screw placement in spinal surgery. Facet angle ≥ 45° is independently associated with both the intra-pedicular accuracy and proximal FJV.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03271-6.

The Mini-Open Wiltse Approach with Pedicle Screw Fixation Versus Percutaneous Pedicle Screw Fixation for Treatment of Neurologically Intact Thoracolumbar Fractures: A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of the present study was to compare the clinical outcomes and complications between the mini-open Wiltse approach with pedicle screw fixation (MWPSF) and percutaneous pedicle screw fixation (PPSF) in treating neurologically intact thoracolumbar fractures.

METHODS

We comprehensively searched PubMed, Web of Science, Embase, and the Cochrane Library and performed a systematic review and meta-analysis of all randomized controlled trials and retrospective comparative studies assessing these important indexes of the 2 methods using Review Manager, version 5.4. The clinical outcomes are presented as the risk difference for dichotomous outcomes and the mean difference for continuous outcomes with the 95% confidence intervals. Heterogeneity was assessed using the χ² test and I² statistics. The study was registered with PROSPERO (CRD 42021290078).

RESULTS

Two randomized controlled trials and six retrospective cohort studies were included in the present analysis. The percutaneous approach was associated with less intraoperative blood loss compared with the mini-open Wiltse approach. No significant differences were found in the total length of the incisions, hospitalization time, postoperative visual analog scale scores, postoperative Oswestry disability index, postoperative Cobb angle, postoperative Cobb angle correction, postoperative Cobb angle correction loss, accuracy rate of pedicle screw placement, and postoperative complications between MWPSF and PPSF. However, the incidence of facet joint violation was significantly higher in the PPSF group. In addition, MWPSF was associated with a shorter operative time, shorter intraoperative fluoroscopy time, lower hospitalization costs, better postoperative vertebral body angle and percentage of vertebral body height compared with PPSF.

CONCLUSIONS

Both MWPSF and PPSF are safe and effective treatments of neurologically intact thoracolumbar fractures. Nevertheless, our results have indicated that MWPSF might be the better choice, because it has a shorter learning curve and decreased facet joint violation, operative time, hospitalization costs, and radiation exposure. In addition, MWPSF was associated with better improvement of the postoperative vertebral body angle and percentage of vertebral body height.

Effection of monoplanar pedicle screw on facet joint degeneration in thoracolumbar vertebral fractures

Background

This study aimed to compare the clinical outcomes and effect on instrument-related facet joints between fixed-axis pedicle screw (FAPS) and monoplanar pedicle screw (MPPS).

Methods

816 pedicle screws of 204 patients with thoracolumbar vertebral fractures (TLVF) who underwent internal fixation surgery were analyzed in this retrospective study. All patients were divided into two groups (FAPS and MPPS). Preoperative, immediate postoperative, and 12–18-months postoperative CT and X-ray, and clinical data, including demographics, preoperative and immediate postoperative Visual Analogue Scale (VAS), blood loss (BL), operation time (OT) and hospital stay time (HST), were collected. Facet joint violation and degeneration grade were evaluated by CT according to Babu’s criteria and Weishaupt’s criteria respectively, and preoperative, immediate postoperative and 12–18-months postoperative anterior body compression index (ABCI) were measured by X-ray.

Results

Postoperative VAS of two groups was lower than preoperative VAS (p < 0.05). BL, OT, and HST were less in MPPS than FAPS, and the difference was statistically significant in BL and HST (p < 0.05) but no in OT (p > 0.05). Immediate postoperative and 12–18-months postoperative ABCI were significantly higher than preoperative (p < 0.05), and the difference of ABCI between immediate postoperative and 12–18-months postoperative were not significant in two groups (p > 0.05). Total violation rate (VR) was about 1.35% (11/816) and FAPS had a lower VR than MPPS, but no significant (p > 0.05). Weishaupt’s criteria revealed that average class (AC) was 0.69 in FAPS and 0.67 in MPPS, and the distribution of degenerated facet joints in two groups did not differ preoperatively (p > 0.05). In 12–18 months postoperatively, AC was significantly higher in FAPS than in MPPS, and the distribution of degenerated facet joints in two groups was significantly different (p < 0.05). The comparison of cranial to caudal joints in two groups revealed that cranial joints had more severe degeneration than caudal joints.

Conclusions

The findings suggested that both MPPS and FAPS were effective for patients with TLVF, but MPPS by percutaneous may be a better choice to avoid adjacent segment degeneration, especially the surgery-involved facet joints degeneration.

Facet Violation With Percutaneous Pedicle Screw Placement: Impact of 3D Navigation and Facet Orientation

Background: The gold standard for percutaneous pedicle screw placement is 2-dimensional (2D) fluoroscopy. Data are sparse on the accuracy of 3-dimensional (3D) navigation percutaneous screw placement in minimally invasive spine procedures. Objective: We sought to compare a single surgeon's percutaneous pedicle screw placement accuracy using 2D fluoroscopy versus 3D navigation, as well as to investigate the effect of facet orientation on facet violation when using 2D fluoroscopy. Methods: We conducted a retrospective radiographic study of consecutive cohort of patients who underwent percutaneous lumbar instrumentation using either 2D fluoroscopy or 3D navigation. All procedures were performed by a single surgeon at 2 academic institutions between 2011 and 2018. Radiographic measurement of screw accuracy was assessed using a postoperative computed tomographic scan. The primary outcome was facet violation, and secondary outcomes were endplate/tip breaches, the Gertzbein-Robbins classification for cortical breaches, and the Simplified Screw Accuracy grade. Statistical comparisons were made between screws placed using 2D fluoroscopy versus 3D navigation. Axial facet angles were also measured to correlate with facet violation rates. Results: In the 138 patients included, 376 screws were placed with fluoroscopy and 193 with navigation. Superior (unfused) level facet violation was higher with 2D fluoroscopy than with 3D navigation (9% vs 0.5%), which comprises the main cause for poor screw placement. Axial facet angles exceeding 45° at L4 and 60° at L5 were correlated with facet violations. Conclusion: This retrospective study found that 3D navigation is associated with lower facet violation rates in percutaneous lumbar pedicle screw placement when compared with 2D fluoroscopy. These findings suggest that 3D navigation may be of particular value when facet joints are coronally oriented.

Facet Joint Violation by Thoracolumbar Percutaneous Pedicle Screw and Its Effect on Progression of Facet Joint Osteoarthritis

Study Design

A retrospective study.

Purpose

This study aimed to investigate the rate and associated factors of facet violation (FV) in percutaneous pedicle screws (PPS) from the thoracic to the lumbar spine and the effect of FV on facet osteoarthritis (OA) progression.

Overview of Literature

Some reports claim PPS has a higher FV rate than conventional open surgery. However, previous reports of FV in PPS were limited to the lumbar spine; only a few reports included the thoracic spine.

Methods

The present study includes 1,028 PPS inserted from T4 to S1 in 218 patients. The rate of FV and facet OA progression after FV were assessed using computed tomography (CT) scans conducted postoperatively at 1 week and 6 months or more. To identify factors associated with FV or facet OA progression after FV, a multivariate logistic regression analysis was conducted. To investigate whether FV caused facet OA progression, we compared OA progression between patients with FV and matched controls.

Results

FV was observed in 68 (6.6%) of the 1,028 facets, and the thoracic spine was identified as an independent factor associated with FV. OA progression was detected in 48.2% of the cases with FV via CT scans conducted postoperatively at a mean duration of 22.6 months. The time between CT scans was identified as an independent factor for facet OA progression after FV. The rate of OA progression in patients with FV was significantly greater than that of the controls.

Conclusions

FV was observed in 6.6% of the patients, and the thoracic spine was identified as an independent factor associated with FV. OA progression of a violated facet occurs over time. FV is considered a complication leading to facet OA progression.

Characterization and rate of symptomatic adjacent-segment disease after index lateral lumbar interbody fusion: a single-institution, multisurgeon case series with long-term follow-up

OBJECTIVE

The rate of symptomatic adjacent-segment disease (ASD) after newer minimally invasive techniques, such as lateral lumbar interbody fusion (LLIF), is not known. This study aimed to assess the incidence of surgically significant ASD in adult patients who have undergone index LLIF and to identify any predictive factors.

METHODS

Patients who underwent index LLIF with or without additional posterior pedicle screw fixation between 2010 and 2012 and received a minimum of 2 years of postoperative follow-up were retrospectively included. Demographic and perioperative data were recorded, as well as radiographic data and immediate perioperative complications. The primary endpoint was revision surgery at the level above or below the previous construct, from which a survivorship model of patients with surgically significant symptomatic ASD was created.

RESULTS

Sixty-seven patients with a total of 163 interbody levels were included in this analysis. In total, 17 (25.4%) patients developed surgically significant ASD and required additional surgery, with a mean ± SD time to revision of 3.59 ± 2.55 years. The mean annual rate of surgically significant ASD was 3.49% over 7.27 years, which was the average follow-up. One-third of patients developed significant disease within 2 years of index surgery, and 1 patient required surgery at the adjacent level within 1 year. Constructs spanning 3 or fewer interbody levels were significantly associated with increased risk of surgically significant ASD; however, instrument termination at the thoracolumbar junction did not increase this risk. Surgically significant ASD was not impacted by preoperative disc height, foraminal area at the adjacent levels, or changes in global or segmental lumbar lordosis.

CONCLUSIONS

The risk of surgically significant ASD after LLIF was similar to the previously reported rates of other minimally invasive spine procedures. Patients with shorter constructs had higher rates of subsequent ASD.

Robotic-Navigated Percutaneous Pedicle Screw Placement Has Less Facet Joint Violation Than Fluoroscopy-Guided Percutaneous Screws

OBJECTIVE

To directly compare robotic-versus fluoroscopy-guided percutaneous pedicle screw (PPS) placement in thoracolumbar spine trauma with a focus on clinically acceptable pedicle screw accuracy and facet joint violation (FJV).

METHODS

A retrospective chart review assessed 37 trauma patients undergoing percutaneous thoracic and/or lumbar fixation. Postoperative computed tomography images were reviewed by authors blinded to surgical technique who assessed pedicle screw trajectory accuracy and FJV frequency.

RESULTS

Seventeen patients underwent placement of 143 PPS with robotic assistance (robot group), compared with 20 patients receiving 149 PPS using fluoroscopy assistance (control group). Overall, the robot cohort demonstrated decreased FJV frequency of 2.8% versus 14.8% in controls (P = 0.0003). When further stratified by level of surgery (i.e., upper thoracic, lower thoracic, lumbar spine), the robot group had FJV frequencies of 0%, 3.2%, and 3.7%, respectively, compared with 17.7% (P = 0.0209), 14.3% (P = 0.0455), and 11.9% (P = 0.2340) in controls. The robot group had 84.6% clinically acceptable screw trajectories compared with 81.9% in controls (P = 0.6388). Within the upper thoracic, lower thoracic, and lumbar regions, the robot group had acceptable screw trajectories of 66.7%, 87.1%, and 90.7%, respectively, compared with 58.8% (P = 0.6261), 91.1% (P = 0.5655), and 97.6% (P = 0.2263) in controls.

CONCLUSIONS

There was no significant difference in clinically acceptable screw trajectory accuracy between robotic versus fluoroscopy-guided PPS placement. However, the robot cohort demonstrated a statistically significantly decreased FJV overall and specifically within the thoracic spine region. Use of robotic technology may improve radiographic outcomes for a subset of patients or spine surgeries.

Appropriate insertion point for percutaneous pedicle screw placement in the lumbar spine using c-arm fluoroscopy: a cadaveric study

Background

We studied the characteristics and regularity of appropriate insertion points for percutaneous pedicle screw placement in the lumbar spine using C-arm X-ray fluoroscopy. The purpose of this study was to improve the accuracy of percutaneous pedicle screw placement and reduce the incidence of superior-level facet joint violation.

Methods

Six normal spinal specimens were included. Three different methods for placing percutaneous pedicle screws in the lumbar spine were applied, including the Roy-Camille method, Magerl method and Weinstein method. The relationships among the insertion point, pedicle projection and proximal facet joint on C-arm X-ray films were studied. The projection morphology of the vertebral pedicle in different segments of the lumbar spine was observed. The relationship between the outer edge of the pedicle projection and the outer edge of the cranial articular process was also studied. The distance between the insertion point and the facet joint (M1), the distance between the insertion point and outer edge of the cranial articular process (M2), and the distance between the insertion point and the projection center of the pedicle (M) were measured.

Results

In this study, we found that the projection shape of the vertebral pedicle differed across segments of the lumbar spine: the shape for L1-L3 was oval, and that for L4-L5 was round. The radiographic study showed that the outer edge of the cranial articular process was located on the lateral side of the outer edge of the pedicle projection and did not overlap with the pedicle projection. M for the Weinstein group was larger than that for the Roy-Camille group (P <  0.05). M1 for the Weinstein group was larger than that for the Roy-Camille and Magerl groups (P <  0.05). M2 for the Roy-Camille group was negative, M2 for the Magerl group was 0, and M2 for the Weinstein group was positive.

Conclusion

Under C-arm X-ray fluoroscopy, we were able to accurately identify the characteristics and regularity of the appropriate insertion point for percutaneous pedicle screw placement in the lumbar spine, which was important for improving the accuracy of percutaneous pedicle screw placement and reducing the incidence of superior-level facet joint violation.

Accuracy of fluoroscopic guidance with the coaxial view of the pedicle for percutaneous insertion of lumbar pedicle screws and risk factors for pedicle breach

OBJECTIVE

In this study the authors aimed to evaluate the rate of malposition, including pedicle breach and superior facet violation, after percutaneous insertion of pedicle screws using the coaxial fluoroscopic view of the pedicle, and to assess the risk factors for pedicle breach.

METHODS

In total, 394 percutaneous screws placed in 85 patients using the coaxial fluoroscopic view of the pedicle between January 2014 and September 2017 were assessed, and 445 pedicle screws inserted in 116 patients using conventional open procedures were used for reference. Pedicle breach and superior facet violation were evaluated by postoperative 0.4-mm slice CT.

RESULTS

Superior facet violation was observed in 0.5% of the percutaneous screws and 1.8% of the conventionally inserted screws. Pedicle breach occurred more frequently with percutaneous screws (28.9%) than with conventionally inserted screws (11.9%). The breaches in percutaneous screws were minor and did not reduce the interbody fusion rate. The angle difference between the percutaneous and conventionally inserted screws was comparable. Insertion at the L3 or L4 level, right-sided insertion, placement around a trefoil canal, smaller pedicle angle, and a small difference between the screw and pedicle diameters were found to be risk factors for pedicle breach by percutaneous pedicle screws.

CONCLUSIONS

Percutaneous pedicle screw placement using the coaxial fluoroscopic view of the pedicle carries a low risk of superior facet violation. The screws should be placed carefully considering the level and side of insertion, canal shape, and pedicle angle.

Does Pedicle Screw Fixation Assisted by O-Arm Navigation Perform Better Than Fluoroscopy-guided Technique in Thoracolumbar Fractures in Percutaneous Surgery?: A Retrospective Cohort Study

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To evaluate the effect of O-arm navigation in percutaneous surgeries for thoracolumbar fracture in comparison to the use of conventional fluoroscopic technique.

SUMMARY OF BACKGROUND DATA

O-arm navigation is a progressive surgical tool, with extensive research papers reporting its effects. Whereas, there were not many papers describing its accuracy and facet impingement rate when compared with fluoroscopy-guided technique in percutaneous surgeries, especially at varying fracture levels.

MATERIALS AND METHODS

We conducted a retrospective comparative study of 97 consecutive patients of single-level neurological intact thoracolumbar fractures from November 2015 to October 2017 and they were all treated with percutaneous pedicle screw implantation. Screws were classified as 4 grades of perforations and 3 grades of facet joint violation. The association between variables such as anatomic perforation, functional perforation, and facet impingement were investigated by χ test, Fisher exact test or t test. A P-value of <0.05 was considered statistically significant.

RESULTS

A total of 573 pedicle screws were implanted and graded. The overall anatomic perforation rate and functional perforation rate were lower in the O-arm group compared with the fluoroscopy group (8.3% vs. 15.0%, P=0.013, 1.1% vs. 4.2%, P=0.024). At fracture level, the rate of grade 2 perforation of the O-arm group was lower than that of the fluoroscopy group (0% vs. 6.1%, P=0.033). Furthermore, the O-arm group obviously reduced the facet impingement rate both at all levels and at fracture levels (P=0.002; 0.02).

CONCLUSIONS

In percutaneous pedicle screw placement for neurological intact thoracolumbar fracture, the introduction of O-arm navigation improved accuracy, reduced functional perforations, and minimized serious perforations compared with conventional fluoroscopic technique. It also decreased facet joint violation observably and helped to prevent development of adjacent segment degeneration.

Superior-segment Bilateral Facet Violation in Lumbar Transpedicular Fixation, Part III: A Biomechanical Study of Severe Violation

MINI: In controls, adjacent-level range of motion (ROM) did not change relative to noninstrumented spine at each moment. In severe violation, flexion-extension and rotation ROM of adjacent vertebrae decreased at each moment (7.5, 6.0, 4.5 Nm); lateral bending ROM decreased at 4.5 Nm. Significant differences in movements were found except lateral bending (7.5 Nm).

STUDY DESIGN

This is an in vitro biomechanical study.

OBJECTIVES

This study aimed to investigate the biomechanical variations of lumbar spine motor units after bilateral facet joint severe violation in cadaver specimens and analyze the biomechanics under different moments.

SUMMARY OF BACKGROUND DATA

The incidence of facet joint violation (FJV) is highly variable, and one of the most important factors is the lack of awareness of protection. Until now, the biomechanical effects of FJV remain unclear.

METHODS

Biomechanical testing was performed on 12 human cadaveric spines under flexion-extension, lateral bending, and axial rotation loading. After intact analysis, pedicle screws were inserted at L5, and the biomechanical testing was repeated. Full range of motion (ROM) at the proximal adjacent levels under different moments was recorded and normalized to the intact (100%) noninstrumented spine. The relative ROM changes were compared between the control and severe violation groups.

RESULTS

The adjacent-level ROM (flexion-extension, lateral bending, axial rotation) did not change significantly in the control group at each moment (7.5, 6.0, 4.5 Nm) compared with the intact noninstrumented spine. In the severe violation group, the supradjacent-level ROM decreased significantly under all moments relative to the intact noninstrumented spine (P < 0.05) except for the ROM of lateral bending at moments of 7.5 and 6.0 Nm. When comparing the ROM between the two groups, there were significant differences in all movements except lateral bending at 7.5 Nm.

CONCLUSION

When superior-segment bilateral facet joints are severely violated by screws, the flexion-extension and axial rotation ROM of adjacent vertebrae decreases at each moment (7.5, 6.0, 4.5 Nm), and the lateral bending ROM decreases at 4.5 Nm.

LEVEL OF EVIDENCE

N/A.

Risk Factors Related to Superior Facet Joint Violation During Lumbar Percutaneous Pedicle Screw Placement in Minimally Invasive Transforaminal Lumbar Interbody Fusion (MIS-TLIF)

OBJECTIVE

To investigate the incidence of superior facet joint violation (FJV) during percutaneous pedicle screw placement in minimally invasive transforaminal lumbar interbody fusion, and assess the possible risk factors for FJV.

METHODS

An analysis of 91 patients with lumbar degenerative diseases treated with percutaneous pedicle screw placement via minimally invasive transforaminal lumbar interbody fusion from 2012 to 2018 was performed. Superior FJV was evaluated and graded by 3-dimensional lumbar computed tomography reconstruction. Analysis of possible risk factors included general condition of patients, anatomical characteristics of facet joint (FJ; axial, sagittal, and coronal diameters of FJ, facet angle, lumbar lordosis angle, lumbar lordosis index, and depth of lamina), and surgical factors (pedicle screw angle, screw-superior FJ distance, cranial angle, proximal rod length, and rod contouring).

RESULTS

The overall violation rate of superior FJ was 34.07% (62/182), and high-grade violation rate was 16.06% (27/182). The logistic regression analysis revealed that body mass index ≥30 kg/m² and pedicle screw placement at L5 were independent risk factors of FJV. Anatomical factors showed that the incidence of FJV was significantly increased when axial, sagittal, and coronal diameters of FJ were all ≥12 mm or FA was ≥40°. Surgical factors showed that the FJV group had a smaller pedicle screw angle and screw-superior FJ distance compared with the non-FJV group (P < 0.05).

CONCLUSIONS

Body mass index ≥30 kg/m² and pedicle screw placement at L5 were independent risk factors of superior FJV. FJV was more likely to occur in hypertrophic FJ (axial, sagittal, and coronal diameters ≥12 mm) or coronal orientation (FA ≥40°).

Minimally Invasive Spine (MIS) Surgery in Traumatic Thoracolumbar Fractures: A Single-Center Experience

Objective:

Traumatic thoracolumbar fractures are common, and surgical fixation is a well-established treatment option, with the aim to achieve spinal stability and preserve neurological function. Pedicle screw fixation using a minimally invasive spine (MIS) surgical approach has emerged as an alternative approach for the treatment of thoracolumbar fractures. The aim of this study is to collect data regarding epidemiology, management, and outcomes of patients treated with MIS pedicle screw fixation for traumatic thoracolumbar fractures in our neurosurgical department.

Materials and Methods:

This was a retrospective cohort study including all patients who underwent MIS fixation from March 2013 to March 2017.

Results:

A total of 125 patients were included, 61 males and 64 females; the mean age was 59 years. The majority of injuries were from falls. In 48 cases, the fracture involved a thoracic vertebra and in 77 cases a lumbar vertebra. More than 10% of the patients presented with a neurological deficit on admission and 75% of those showed postoperative improvement in their neurology. The average length of hospital stay was 14 days. MIS fixation achieved a satisfactory regional sagittal angle (RSA) postoperatively in all patients. The vast majority of patients had no or mild postoperative pain and achieved a good functional outcome.

Conclusions:

MIS fixation is a safe surgical option with comparable outcomes to open surgery and a potential reduction in perioperative morbidity. MIS surgery achieves a rapid and significant improvement in pain score, functional outcome, Frankel Grade, and RSA. We expect that MIS fixation will become the predominant technique in the management of traumatic thoracolumbar fractures.

Comparison of facet joint violation in lumbar posterior spinal instrumentation using different techniques including cortical bone trajectory

Study background:

A retrospective study to compare the rate of facet joint violation (FJV) in lumbar posterior spinal instrumentation using open pedicle screw, percutaneous pedicle screw, and cortical bone trajectory (CBT) technique. CBT is a new posterior spinal instrumentation technique in which a more caudal entry point can minimize iatrogenic damage to the cranial facet joint. Only one recent study reports incidence of FJV of 11%; however, no previous reports comment on radiological outcomes comparing to traditional open and percutaneous screws.

Methods:

We reviewed 90 patients who underwent lumbar posterior spinal instrumentation from January 2016 to June 2017. Postoperative computer tomography scans were performed to evaluate FJV. Incidence of FJV was graded by three reviewers according to Seo classification.

Results:

Totally, 446 screws (open 43.4%, percutaneous 37.8%, CBT 18.9%) were inserted. Among these, 6.3% (28/446) had screw head or rod in contact with facet joint and 0.9% (4/446) had screws directly invaded the facet joint. Overall, FJV was 7.2% (CTB = 3.4%, open = 10.4%, and percutaneous = 4.5%, p = 0.075).

Conclusion:

CBT technique has potential advantage in reducing FJV. It has a unique entry site at lateral aspect of pars interarticular with a caudomedial to craniolateral pathway. It is a reasonable alternative to open or percutaneous techniques in lumbar posterior spinal instrumentation.

Superior Facet Joint Violations in Single Level Minimally Invasive and Open Transforaminal Lumbar Interbody Fusion: A Comparative Study

Study Design

Prospective comparative study.

Purpose

To compare the incidence of iatrogenic superior facet joint violation (SFV) in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and open TLIF (OPEN-TLIF) at a single lower lumbar fusion level and to evaluate the patient and surgical factors influencing the outcome.

Overview of Literature

Iatrogenic SFV is a significant risk factor for adjacent segment disease (ASD). Blind screw placement technique in MIS-TLIF contributes to the increasing incidence of iatrogenic SFV which can be influenced by several other potential factors. There are only limited studies comparing the incidence of iatrogenic SFV in MIS-TLIF and OPEN-TLIF.

Methods

In total, 225 cases (450 top screws; MIS-TIFL, 120; OPEN-TILF, 105) undergoing single-level lower lumbar fusion were included in the study. Postoperative computed tomography grading system was used to evaluate iatrogenic SFV. Patient and surgical factors such as age, body mass index, top-screw level, side of the top screw, depth of the spine, and superior facet joint angle (SFA) were analyzed in iatrogenic SFV and non-violation groups to determine their influence on iatrogenic SFV. The clinical outcomes in both groups were assessed preoperatively and postoperatively.

Results

The overall incidence of iatrogenic SFV and high-grade violations was higher in MIS-TLIF (41.25%) than in OPEN-TLIF (30.4%). In both groups, bivariate analysis showed a significantly greater incidence of the iatrogenic SFV in patients aged <60 years and those with obesity, top pedicle screws at L4, right-sided top screws, SFA >35°, and depth of the spine >50 mm.

Conclusions

This study demonstrated that the incidence of iatrogenic SFV is greater in MIS-TLIF than in OPEN-TLIF at a single lower lumbar level. MIS-TLIF is effective for lumbar degenerative disease; however, the incidence of iatrogenic SFV was higher. Patient and surgical factors must be considered to protect the facet joints in both TLIF methods to avoid ASD.

Suboccipital neuralgia after C1 pedicle screw insertion: do we neglect atlantooccipital joint violation? - Case report and literature review

Background

Occipital neuralgia is one of the postoperative complications of C1 lateral mass screw insertion, which was deemed to be related with the C2 nerve root dysfunction.

Case presentation

A 52-year-old female patient presented with gradually progressive numbness and weakness in her extremities for 6 months. X-ray and computed tomography (CT) scan revealed obvious anterior atlantoaxial dislocation (ADD), which was reducible on extensive view. Atlantoaxial pedicle screw fixation and bone graft was performed. Immediately after the operation, the neurological symptom significantly improved. The patient complained of restricted cervical rotation and suboccipital neuralgia which was exacerbated by rotation with an intensity of 7 on a visual analog scale (VAS) ranging from 0 to 10 at postoperative day 5. While a satisfactory reduction was detected in the postoperative CT, violation of the left atlantooccipital joint was observed in the left C1 screw. Nimesulide (daily dosage of 0.2 g) and bracing were recommended immediately. At the 2 month follow-up, both the neurological improvement and reduction were maintained. The VAS of suboccipital neuralgia is 3 and decreased to 1 at 6 months postoperative. Bony fusion of the left atlantooccipital joint was confirmed by CT scan at 6 months postoperative. The patient complained that the suboccipital neuralgia was tolerable without the assistance of braces or medications for pain. At the 18 month follow-up, only stiffness of head flexion and rotation was observed without suboccipital neuralgia.

Conclusion

Suboccipital neuralgia after atlantooccipital joint violation of C1 pedicle screw placement most likely results from C1 nerve root irritation. As the corresponding dermatome differs from the distributing region and aggravated factor of C2 nerve root dysfunction, neuralgia due to C1 irritation was only localized at suboccipital region and exacerbated by rotation.

The use of robotics in minimally invasive spine surgery

The field of spine surgery has changed significantly over the past few decades as once technological fantasy has become reality. The advent of stereotaxis, intra-operative navigation, endoscopy, and percutaneous instrumentation have altered the landscape of spine surgery. The concept of minimally invasive spine (MIS) surgery has blossomed over the past ten years and now robot-assisted spine surgery is being championed by some as another potential paradigm altering technological advancement. The application of robotics in other surgical specialties has been shown to be a safe and feasible alternative to the traditional, open approach. In 2004 the Mazor Spine Assist robot was approved by FDA to assist with placement of pedicle screws and since then, more advanced robots with promising clinical outcomes have been introduced. Currently, robotic platforms are limited to pedicle screw placement. However, there are centers investigating the role of robotics in decompression, dural closure, and pre-planned osteotomies. Robot-assisted spine surgery has been shown to increase the accuracy of pedicle screw placement and decrease radiation exposure to surgeons. However, modern robotic technology also has certain disadvantages including a high introductory cost, steep learning curve, and inherent technological glitches. Currently, robotic spine surgery is in its infancy and most of the objective evidence available regarding its benefits draws from the use of robots in a shared-control model to assist with the placement of pedicle screws. As artificial intelligence software and feedback sensor design become more sophisticated, robots could facilitate other, more complex surgical tasks such as bony decompression or dural closure. The accuracy and precision afforded by the current robots available for use in spinal surgery potentially allow for even less tissue destructive and more meticulous MIS surgery. This article aims to provide a contemporary review of the use of robotics in MIS surgery.

Incidence and risk factors of facet joint violation following percutaneous kyphoplasty for osteoporotic vertebral compression fractures

BACKGROUND

Percutaneous kyphoplasty (PKP) has been widely used to osteoporotic vertebral compression fractures (OVCFs). No previous investigations have reported the incidence and risk factors of facet joint violation (FJV) caused by PKP.

PURPOSE

To determine the incidence and risk factors of FJV following PKP in patients with OVCFs.

MATERIAL AND METHODS

We reviewed a total of 153 patients who underwent bilateral PKP. Postoperative computed tomography (CT) scans were assessed to determine the degree of FJV owing to invasion by a puncture trocar. Clinical outcomes, including visual analogue scale (VAS) scores and Oswestry Disability Index (ODI) scores, were collected from all patients. Clinical and radiological data were analyzed to identify the risk factors for FJV.

RESULTS

FJV caused by PKP affected 18.9% of patients and 9.6% of facet joints; approximately 3.9% and 5.7% of facet joints were considered to have grade 1 and grade 2 violations, respectively. There were significant differences between the FJV and non-FJV groups in VAS and ODI scores after surgery. Significant differences were found with respect to the facet joint angle (FJA), the pedicle diameter (PD), and the distance from the entry point to the facet joint space (DEF). Multiple logistic regression analysis indicated that an FJA > 55°, a PD < 5 mm, and a DEF < 5 mm were independent risk factors for FJV.

CONCLUSION

The placement of a puncture trocar can cause FJV in patients with OVCFs and impact clinical outcomes after PKP. Special attention should be given to patients with an FJA > 55°, a PD < 5 mm, and a DEF < 5 mm.

Adjacent-segment disease following two-level axial lumbar interbody fusion

OBJECTIVE

While long-term studies have evaluated adjacent-segment disease (ASD) following posterior lumbar spine arthrodesis, no such studies have assessed the incidence and prevalence of ASD following axial lumbar interbody fusion (AxiaLIF). The aim of this study was to estimate the incidence of ASD following AxiaLIF.

METHODS

The authors retrospectively reviewed the medical records of 149 patients who underwent two-level index AxiaLIF and had at least 2 years of radiographic and clinical follow-up. ASD and pre- and postoperative lumbar lordosis were evaluated in each patient. ASD was defined as both radiographic and clinically significant disease at a level adjacent to a previous fusion requiring surgical intervention. The mean duration of follow-up was 6.01 years.

RESULTS

Twenty (13.4%) of the 149 patients developed ASD during the data collection period. Kaplan-Meier analysis predicted a disease-free ASD survival rate of 95.3% (95% CI 90.4%-97.7%) at 2 years and 89.1% (95% CI 82.8%-93.2%) at 5 years for two-level fusion. A laminectomy adjacent to a fusion site was associated with 5.1 times the relative risk of developing ASD. Furthermore, the ASD group had significantly greater loss of lordosis than the no-ASD group (p = 0.033).

CONCLUSIONS

Following two-level AxiaLIF, the rate of symptomatic ASD warranting either decompression or arthrodesis was found to be 4.7% at 2 years and 10.9% at 5 years. Adjacent-segment decompression and postoperative loss of lumbar lordosis predicted future development of ASD. To the authors' knowledge, this is the largest reported cohort of patients to undergo two-level AxiaLIF in the United States.

The Concept for A Standalone Lordotic Endoscopic Wedge Lumbar Interbody Fusion: The LEW-LIF

OBJECTIVE

To review concepts of a standalone endoscopically assisted lumbar interbody fusion as a simplified method to treat spinal instability.

METHODS

MacNab outcomes and complications were analyzed in a series of 48 consecutive patients who underwent standalone lordotic endoscopic wedge lumbar interbody fusion (LEW-LIF) for advanced lumbar disc degeneration, spinal stenosis, and spondylolisthesis.

RESULTS

Forty-two of the 48 patients (77.8%) did well with excellent and good outcomes with a follow up of up to 20 months. Fair outcomes were reported by 4, and poor by another 2 patients, respectively. Six patients had endoscopic decompression procedures at another level. Four patients underwent open transforaminal lumbar interbody fusion revision surgery including the index level between 2 to 6 months postoperatively. An L5 vertebral body fracture was noted in 1 of these 4 patients. Another patient underwent removal of the extruded L3/4 cage. The cage fractured in one additional asymptomatic patient not requiring any intervention. No patient had a wound infection, or permanent sensory, or motor dysfunction. However, 29 patients developed a postoperative irritation of the dorsal root ganglion with burning leg pain typically between postoperative weeks 2 and 6. Symptoms were treated with activity modification, gabapentin, and transforaminal epidural steroid injections in 12 patients (25%).

CONCLUSION

Standalone LEW-LIF was associated with favorable clinical outcomes in the majority of patients. Patient-related predictors of less favorable outcomes considering normal variations as well as patho-anatomy may aid in the development of next-generation implants.

Percutaneous fixation of thoracolumbar vertebral fractures

Surgical treatment of patients with thoracolumbar vertebral fracture without neurological deficit is still controversial.

Management of vertebral fracture with percutaneous fixation was first reported in 2004.

Advantages of percutaneous fixation are: less tissue dissection; decreased post-operative pain; decreased bleeding and operative time (depending on the steep learning curve); better screw positioning with fluoroscopy compared with an open freehand technique; and a decreased infection rate.

The limitations of percutaneous fixation of vertebral fractures include increased radiation exposure to the patient and the surgeon, together with the steep learning curve for this technique.

Adding a screw at the level of the fractured vertebra has the advantages of incorporating fewer motion segments with less operative time and bleeding. This also increases the axial, sagittal and torsional stiffness of the construct.

Percutaneous fixation alone without grafting is sufficient for treating type A and B1 (AO classification) thoracolumbar fractures with satisfactory results concerning kyphosis reduction when compared with open instrumentation and fusion and with open fixation.

Type C and B2 fractures (ligamentous injuries) should undergo fusion since the ligamentous healing is mechanically weak, increasing the risk of instability.

This review offers a detailed description of percutaneous screw insertion and discusses the advantages and disadvantages.

Cite this article: EFORT Open Rev 2018;3:604-613. DOI: 10.1302/2058-5241.3.170026.

Anterior Lumbar Interbody Fusion With Cement Augmentation Without Posterior Fixation to Treat Isthmic Spondylolisthesis in an Osteopenic Patient-A Surgical Technique

Background

Anterior lumbar interbody fusion (ALIF) has been well established as an effective surgical intervention for chronic back pain due to osteoporotic vertebral collapse. Historically, ALIF has consisted of an anterior approach to disc height restoration with a subsequent posterior pedicle screw fixation. Although the applications of cement augmentation with posterior fixation have been previously reported, treatment of patients with both isthmic spondylolisthesis and decreased bone mineral density using a stand-alone ALIF is controversial because of concerns for decreased fusion rates and increased subsidence risk, respectively. We report a case of stand-alone ALIF used to treat a low-grade isthmic spondylolisthesis in the setting of idiopathic thoraco-lumbar scoliosis in a patient with secondary degenerative changes and discuss the benefits of this surgical technique in a patient with several comorbidities.

Methods

An osteopenic 66-year-old woman with multiple medical comorbidities and 2 years of left radicular leg pain was found to have a Myerding grade I isthmic spondylolisthesis in the setting of idiopathic thoraco-lumbar scoliosis with secondary changes. The patient underwent an L5-S1 stand-alone ALIF with anterior cement augmentation without posterior pedicle screw fixation.

Results

The patient experienced immediate relief of radicular leg pain postoperatively and had an uneventful course. At 2 years follow-up, she remained symptom free, and radiographs showed excellent fusion and maintenance of intervertebral disc height.

Conclusions

The use of stand-alone ALIF with anterior cement augmentation of the vertebral bodies is a surgical technique that could produce excellent improvement in patients with low-grade isthmic spondylolisthesis in the setting of osteopenia. The use of the all-anterior approach in similar patients with multiple medical comorbidities can also be a useful technique, as it decreases associated morbidity of surgery and complication risks associated with prolonged operative times.

The Impact of Facet Joint Violation on Clinical Outcomes After Percutaneous Kyphoplasty for Osteoporotic Vertebral Compression Fractures

OBJECTIVE

To determine whether the facet joint violation (FJV) impacts clinical outcomes after percutaneous kyphoplasty (PKP) in patients with osteoporotic vertebral compression fractures.

METHODS

Patients undergoing bilateral PKP were enrolled and divided into FJV and non-FJV groups depending on their postoperative axial computed tomography scans. Radiologic parameters, visual analogue scale (VAS), and Oswestry Disability Index (ODI) scores were obtained preoperatively and each follow-up time postoperatively (1day, 1 week, 1 month, 3 months, 6 months, and 1 year). Finally, patient satisfaction surveys also were noted.

RESULTS

A total of 157 patients completed the 1-year follow-up. The incidence of FJV resulting from puncture trocars was 15.9% (25/157). Approximately 5.7% (9/157) and 10.2% (16/157) of patients were considered to have grade 1 and grade 2 violation, respectively. PKP decreased the VAS and ODI scores compared with the preoperative values in both groups. Patients with FJV had much greater VAS and ODI scores than did those without FJV at 1-day, 1-week, and 1-month follow-up. No significant differences were found between groups at 3-month, 6-month, and 1-year follow up. Patients in the FJV group were less satisfied with the surgical outcomes than were those without FJV at the last survey.

CONCLUSIONS

Approximately 15.9% of patients were diagnosed with FJV by postoperative computed tomography scans. FJV had a negative influence on clinical outcomes after PKP in osteoporotic vertebral compression fractures, primarily at short-term follow-up. In addition, FJV was also a risk factor in the long-term surgical satisfaction.

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.

Anatomical and technical factors associated with superior facet joint violation in lumbar fusion

OBJECTIVE The aim of this study was to evaluate the anatomical and surgical risk factors for screw-related facet joint violation at the superior level in lumbar fusion. METHODS The authors conducted a retrospective review of a consecutive series of posterior lumbar instrumented fusions performed by a single surgeon. Inclusion criteria were primary lumbar fusion of 1 or 2 levels for degenerative disorders. The following variables were analyzed as possible risk factors: surgical technique (percutaneous vs open screw placement), depth of surgical field, degree of anterior slippage of the superior level, pedicle and facet angle, and facet degeneration of the superior level. Postoperative CT scans were evaluated by 2 independent reviewers. Axial, sagittal, and coronal views were reviewed. Pedicle screws were graded as intra-articular if they clearly interposed between the superior and inferior facet joints of the superior level. Multivariate logistic regression analyses were conducted to assess the factors associated with this complication. RESULTS One hundred thirty-one patients were included. Interobserver reliability for facet joint violation assessment was high (κ = 0.789). The incidence of superior facet joint violation was 12.59% per top-level screw (33 of 262 proximal screws). The rate of facet violation was 28.0% in the percutaneous technique group (14 of 50 patients) and 12.3% in the open surgery group (10 of 81 patients) (OR 2.26, 95% CI 1.09-4.21; p = 0.024). In multivariate logistic regression analysis, independent predictors of facet violation were percutaneous screw placement (adjusted OR 3.31, 95% CI 1.42-7.73; p = 0.006), right-side pedicle screw (adjusted OR 3.14, 95% CI 1.29-7.63; p = 0.011), and facet angle > 45° (adjusted OR 10.95, 95% CI 4.64-25.84; p < 0.0001). CONCLUSIONS The incidence of facet joint violation was higher in percutaneous minimally invasive than in open technique for posterior lumbar spine surgery. Also, coronal orientation of the facet joint is a significant risk factor independent of the surgical technique.

Percutaneous screw placement in the lumbar spine with a modified guidance technique based on 3D CT navigation system

Several guidance techniques have been employed to increase accuracy and reduce surgical time during percutaneous placement of pedicle screws (PS). The purpose of our study was to present a modified technique for percutaneous placement of lumbar PS that reduces surgical time. We reviewed 23 cases of percutaneous PS placement using our technique for minimally invasive lumbar surgeries and 24 control cases where lumbar PS placement was done via common technique using Jamshidi needles (Becton, Dickinson and Company, Franklin Lakes, NJ, USA). An integrated computer-guided navigation system was used in all cases. In the technique modification, a handheld drill with a navigated guide was used to create the path for inserting guidewires through the pedicles and into the vertebral bodies. After drill removal, placement of the guidewires through the pedicles took place. The PS were implanted over the guidewires, through the pedicles and into the vertebral bodies. Intraoperative computed tomography was performed after screw placement to ensure optimal positioning in all cases. There were no intraoperative complications with either technique. PS placement was correct in all cases. The average time for each PS placement was 6.9 minutes for the modified technique and 9.2 minutes for the common technique. There was no significant difference in blood loss. In conclusion, this modified technique is efficient and contributes to reduced operative time.

Stand-alone anterior lumbar interbody fusion - complications and perioperative results

OBJECTIVES

Historically, anterior lumbar interbody fusion (ALIF) was related to high rates of intraoperative complications and adverse events related to interbody devices. In recent decades, there have been technical adjustments, and cages that are more suitable have emerged. The aim of this study is to evaluate the efficacy and complication rate of the use of stand-alone mini-ALIF using a self-locking cage.

METHODS

Retrospective single center study. Inclusion criteria: retroperitoneal mini-ALIF for single-level fusion (L5S1); self-locking cage; DDD/stenosis and grade I spondylolisthesis. Exclusion criteria: posterior supplementation, previous fusion/arthroplasty. Endpoints: surgery data, intraoperative and perioperative adverse events related both to surgical access and to the intersomatic device.

RESULTS

Eighty-seven cases were enrolled. Median surgical time was 90 min; median blood loss was 100 mL. The median length of stay in the ICU was zero days; median hospital stay was one day. Ten cases had an adverse event (11.5%): four major adverse events (4.6%; 3 L bleeding; DVT; retroperitoneal haematoma; incisional hernia), and seven minor events (8%; peritoneum injury; minor vascular injury; events related to the cage). No cases of retrograde ejaculation were observed. There was improvement in pain, physical restriction, and quality of life (p < 0.001).

CONCLUSIONS

The mini-ALIF procedure performed for single-level fusion at the distal lumbar level demonstrated low adverse event rates related to both the surgical approach and to the intersomatic device, with reduced hospital stay and satisfactory perioperative clinical results.

Facet Joint Violation During Percutaneous Pedicle Screw Placement: A Comparison of Two Techniques

STUDY DESIGN

A comparative study of facet joint violation (FJV) using two percutaneous surgical techniques.

OBJECTIVE

To compare the rate of iatrogenic FJV and medial pedicle wall breach between two methods of percutaneous pedicle screw instrumentation in the thoracic and lumbar spine.

SUMMARY OF BACKGROUND DATA

Variable iatrogenic damage to the facet joints has been reported to occur with percutaneous pedicle screw techniques, compared with the open approach, which has been associated with adjacent segment disease. Technical variations of percutaneous pedicle screw placement may pose different risks to the facet joint.

METHODS

Attending spine surgeons percutaneously placed pedicle screws in seven human cadaveric spines from T2 to L5. At each level, screws were instrumented on one side using the 9 or 3 o'clock reference point of the pedicle on the posteroanterior view with a lateral-to-medial trajectory (LMT) and on the contralateral side using the center of the pedicle with an owl's eye trajectory (OET). Postoperative screw placement was assessed with computed tomography and then open cadaveric dissection. Outcome measures included FJV and medial pedicle wall breach.

RESULTS

Overall, 17 of 105 screws placed with an LMT versus 49 of 105 screws placed with an OET violated or abutted the facet joint (P <0.0001). This significant difference was observed at the thoracic (T2-T10), thoracolumbar (T11-L1), and lumbar (L2-L5) levels (P = 0.003, 0.035, and 0.018, respectively). Medial pedicle wall breach occurred with 11 LMT screws and seven OET screws (P = 0.077), and no breach was considered critical.

CONCLUSION

A significantly higher FJV rate was observed using the OET versus the LMT in the thoracic, thoracolumbar, and lumbar spine. No statistically significant differences in medial pedicle wall breach occurred between the techniques. Thus, the LMT of minimally invasive pedicle screw fixation may reduce iatrogenic damage to the facet joints.

LEVEL OF EVIDENCE

3.

Accuracy of Percutaneous Pedicle Screw Placement: Does Training Level Matter?

STUDY DESIGN

In vitro human cadaveric surgical technique study.

OBJECTIVE

To assess the accuracy of percutaneous pedicle screw placement in a human cadaveric model using standard fluoroscopic guidance technique, compared across varying levels of experience.

SUMMARY OF BACKGROUND DATA

The current literature varies widely in the reported frequency of facet violation during placement of percutaneous pedicle screws. However, as of yet there are no studies examining the effect that training level has on accuracy of placement.

MATERIALS AND METHODS

Four surgeons with differing levels of training (PGY-2, PGY-4, fellow, attending) were evaluated on their accuracy of percutaneous placement of screws in a uniform manner. Each of the 10 cadavers was instrumented from L1 to S1 bilaterally, for a total of 120 screws. Specimens were dissected to evaluate for facet and pedicle wall violations. These were then recorded and analyzed to evaluate for correlation among participating surgeons, laterality, spinal level, and cadaver body mass index.

RESULTS

Of 120 screws placed, there were 35 total violations [26 superior articular facet violations (21.7%), 5 intra-articular facet joint violations (4.2%), and 4 pedicle breaches (3.3%)]. Among the trainees there was no difference in the likelihood of causing a violation (P=0.8863) but there was a difference when compared with the attending surgeon (P=0.0175). Laterality (P=0.1598), spinal level (P=0.3536), and body mass index (P=0.8547) did not correlate with the likelihood of a violation.

CONCLUSIONS

Surgeons of differing training levels are able to safely and accurately place lumbar pedicle screws in a percutaneous manner, with a low likelihood of facet and pedicle wall violations.

Biomechanical advantages of robot-assisted pedicle screw fixation in posterior lumbar interbody fusion compared with freehand technique in a prospective randomized controlled trial-perspective for patient-specific finite element analysis

BACKGROUND CONTEXT

There have been conflicting results on the surgical outcome of lumbar fusion surgery using two different techniques: robot-assisted pedicle screw fixation and conventional freehand technique. In addition, there have been no studies about the biomechanical issues between both techniques.

PURPOSE

This study aimed to investigate the biomechanical properties in terms of stress at adjacent segments using robot-assisted pedicle screw insertion technique (robot-assisted, minimally invasive posterior lumbar interbody fusion, Rom-PLIF) and freehand technique (conventional, freehand, open approach, posterior lumbar interbody fusion, Cop-PLIF) for instrumented lumbar fusion surgery.

STUDY DESIGN

This is an additional post-hoc analysis for patient-specific finite element (FE) model.

PATIENT SAMPLE

The sample is composed of patients with degenerative lumbar disease.

OUTCOME MEASURES

Intradiscal pressure and facet contact force are the outcome measures.

METHODS

Patients were randomly assigned to undergo an instrumented PLIF procedure using a Rom-PLIF (37 patients) or a Cop-PLIF (41), respectively. Five patients in each group were selected using a simple random sampling method after operation, and 10 preoperative and postoperative lumbar spines were modeled from preoperative high-resolution computed tomography of 10 patients using the same method for a validated lumbar spine model. Under four pure moments of 7.5 Nm, the changes in intradiscal pressure and facet joint contact force at the proximal adjacent segment following fusion surgery were analyzed and compared with preoperative states.

RESULTS

The representativeness of random samples was verified. Both groups showed significant increases in postoperative intradiscal pressure at the proximal adjacent segment under four moments, compared with the preoperative state. The Cop-PLIF models demonstrated significantly higher percent increments of intradiscal pressure at proximal adjacent segments under extension, lateral bending, and torsion moments than the Rom-PLIF models (p=.032, p=.008, and p=.016, respectively). Furthermore, the percent increment of facet contact force was significantly higher in the Cop-PLIF models under extension and torsion moments than in the Rom-PLIF models (p=.016 under both extension and torsion moments).

CONCLUSIONS

The present study showed the clinical application of subject-specific FE analysis in the spine. Even though there was biomechanical superiority of the robot-assisted insertions in terms of alleviation of stress increments at adjacent segments after fusion, cautious interpretation is needed because of the small sample size.

One and two level posterior lumbar interbody fusion (PLIF) using an expandable, stand-alone, interbody fusion device: a VariLift® case series

BACKGROUND

Surgical interventions such as posterior lumbar interbody fusion (PLIF) with and without posterior instrumentation are often employed in patients with degenerative spinal conditions that fail to respond to conservative medical management. The VariLift^® Interbody Fusion System was developed as a stand-alone solution to provide the benefits of an intervertebral fusion device without the requirement of supplemental pedicle screw fixation.

METHODS

In this retrospective case series, 25 patients underwent PLIF with a stand-alone VariLift^® expandable interbody fusion device without adjunctive pedicle screw fixation. There were 12 men and 13 women, with a mean age of 57.2 years (range, 33-83 years); single level in 18 patients, 2 levels in 7 patients. Back pain severity was reported as none, mild, moderate, severe and worst imaginable at baseline, 6 and 12 months. Preoperatively, 88% (22 of 25) of patients reported severe back pain.

RESULTS

All patients experienced symptomatic improvement and, by 12 months postoperatively, 71% (15 of 21) of patients reported only mild residual pain. Overall, pain scores improved significantly from baseline to 12 months (P=0.0002). There were no revision surgeries and fusion was achieved 12 of 13 patients (92%) who returned for a 12-month radiographic follow-up. There were three cases of intractable postsurgical pain which required extended hospitalization or pain management, one wound infection and one case of surgical site dehiscence, both treated and resolved during inpatient hospitalization.

CONCLUSIONS

In this single-physician case series, the VariLift^® device used in single or two-level PLIF provided effective symptom relief and produced a high fusion rate without the need for supplemental fixation.

A prospective, randomized, controlled trial of robot-assisted vs freehand pedicle screw fixation in spine surgery

BACKGROUND

The purpose of this study was to compare the accuracy and safety of an instrumented posterior lumbar interbody fusion (PLIF) using a robot-assisted minimally invasive (Robot-PLIF) or a conventional open approach (Freehand-PLIF).

METHODS

Patients undergoing an instrumented PLIF were randomly assigned to be treated using a Robot-PLIF (37 patients) and a Freehand-PLIF (41 patients).

RESULTS

For intrapedicular accuracy, there was no significant difference between the groups (P = 0.534). For proximal facet joint accuracy, none of the 74 screws in the Robot-PLIF group violated the proximal facet joint, while 13 of 82 in the Freehand-PLIF group violated the proximal facet joint (P < 0.001). The average distance of the screws from the facets was 5.2 ± 2.1 mm and 2.7 ± 1.6 mm in the Robot-PLIF and Freehand-PLIF groups, respectively (P < 0.001).

CONCLUSION

Robotic-assisted pedicle screw placement was associated with fewer proximal facet joint violations and better convergence orientations.

Incidence and Risk Factors of Adjacent Cranial Facet Joint Violation Following Pedicle Screw Insertion Using Cortical Bone Trajectory Technique

STUDY DESIGN

Retrospective study evaluating cranial facet joint violation (FJV) by pedicle screws.

OBJECTIVE

The aim of the study was to determine the incidence and risk factors of FJV following screw placement via cortical bone trajectory (CBT).

SUMMARY OF BACKGROUND DATA

CBT is a new minimally invasive technique for lumbar pedicle screw insertion that minimizes muscle dissection. Inserting a screw from a more caudal entry point can reduce iatrogenic damage to the cranial facet joint; however, no previous reports exist describing the incidence of FJV secondary to the CBT technique.

METHODS

We reviewed 202 consecutive patients who underwent lumbar pedicle screw instrumentation using CBT from October 2011 to June 2015. Postoperative CT scans were obtained to determine the degree and incidence of FJV. Clinical and imaging data were analyzed to clarify the risk factors of FJV. The detailed positions of the proximal screws were also investigated and compared between the FJV and non-FJV groups.

RESULTS

The incidence of FJV by the proximal screws was 11.8% (48/404), with no occurrence of intra-articular FJV. Multiple logistic regression analysis revealed that age >70 years, vertebral slip >10%, and adjacent facet joint degeneration (Pathria's grade 2 or 3) were independent factors significantly affecting FJV. There were statistically significant differences between the FJV and non-FJV groups in the facet-screw distance (3.2 ± 1.0 vs. 8.1 ± 2.3 mm, P < 0.01), the cranial angle (25.8 ± 6.3° vs. 29.9 ± 7.6°, P < 0.01), and the lamina-screw head distance (5.6 ± 1.6 vs. 6.4 ± 1.9 mm, P < 0.01).

CONCLUSION

Lumbar pedicle screw placement via CBT would reduce FJV; however, special care should be taken in patients with age >70 years, vertebral slip >10%, and facet degeneration.

LEVEL OF EVIDENCE

3.

Minimally invasive TLIF leads to increased muscle sparing of the multifidus muscle but not the longissimus muscle compared with conventional PLIF-a prospective randomized clinical trial

BACKGROUND CONTEXT

An overload of the paravertebral muscles after surgical intervention is suggested to be the major cause of postoperative pain. In cross-sectional area analyses, increased atrophy of the multifidus muscle (MF) after conventional open versus minimally invasive posterior lumbar interbody fusion (PLIF) has been described. The three-dimensional characteristics of the paravertebral muscles and separate evaluation of the longissimus muscle (LS) have not been addressed in analyses thus far.

PURPOSE

The purpose of the present study was to compare the MF and LS volume atrophy and fatty degeneration between single-level minimally invasive transforaminal lumbar interbody fusion (miTLIF) and conventional midline approach-based PLIF (coPLIF) of L4/L5 or L5/S1 at the index and superior adjacent segments.

DESIGN

This was a prospective, randomized, controlled, non-blinded study.

PATIENT SAMPLE

Fifty patients with single-level segment degeneration (Pfirrmann ≥III and Modic ≥3) of L4/L5 or L5/S1 not requiring decompression were randomly assigned to two groups.

OUTCOME MEASURES

Paraspinal lumbar residual muscle tissue volume, change in the relative fat content of MF and LS at the index and superior adjacent segments, and clinical parameters, including a visual analogue scale (VAS) for low back pain and the Oswestry Disability Questionnaire (ODI) were the outcome measures in this study.

METHODS

Twenty-five patients were treated with miTLIF, and the remaining patients were treated with coPLIF (both with transpedicular fixation). Clinical scoring was performed preoperatively and at 1 week and 12 months postoperatively, and computed tomography was performed at the latter two follow-ups.

RESULTS

The LS damage at the index segment was similar in both groups (3% greater fat content increase in the coPLIF vs. the miTLIF group, p=.032), whereas MF atrophy and degeneration were increased (p<.001) in the coPLIF group. At the adjacent segment, muscle atrophy and increased fatty infiltration (p<.05) were minimal in both muscles but were similar in both groups. Visual analogue scale and ODI scores improved (p<.001), without differences between the groups.

CONCLUSIONS

The muscle damage after miTLIF was inferior to that after coPLIF; spatially, however, the muscle sparing was predominantly attributed to the MF and, surprisingly, not to the LS.

Treatment of Symptomatic Lumbar Disc Degeneration with the VariLift-L Interbody Fusion System: Retrospective Review of 470 Cases

BACKGROUND

Many first generation stand-alone fusion cages required endplate decortication and surgical impaction during the procedure resulting in segmental subsidence, implant migration and loss of lordosis postoperatively. The primary objective of this study was to evaluate radiographically, in a large series of patients, whether engineering and design modifications incorporated in a specific stand-alone, expandable interbody fusion device (VariLift(®)-L) adequately addressed previously recognized deficiencies of stand-alone interbody cages.

METHODS

In this retrospective chart review of 470 patients (642 treated levels), we evaluated radiographic evidence of fusion, subsidence and migration following a one- or two-level PLIF procedure utilizing this stand-alone expandable interbody fusion device. A secondary objective was to corroborate the low morbidity and symptomatic improvements achieved with previous interbody cage devices used to treat symptomatic disc degeneration.

RESULTS

The average postoperative followup was 3.9 ± 1.8 years and a solid fusion rate of 94% was achieved among patients with ≥ 9 months of radiographic followup. Subsidence > 3 mm was noted at 10 levels with no cases of device migration. Composite back pain severity scores improved from 8.5 ± 1.5 preoperatively to 0.8 ± 1.5 at final followup (p<0.001) and 94% of patients met or exceeded the minimal clinical important difference of 3.8 points. Eighteen patients required reoperation following the index procedure; 16 of these patients were treated for adjacent segment disease.

CONCLUSIONS LOE

The VariLift-L device has excellent clinical and technical performance characteristics, providing adequate stabilization of the anterior column without the need for supplemental posterior instrumentation. Level of Evidence IV. IRB Approval: Expedited Federal Register Categories 5& 7: Methodist IRB 3/30/2011; Informed Consent statement: retrospective data collection, patients signed consent forms allowing for data to be used for research.

CLINICAL RELEVANCE

This stand-alone expandable fusion device produced high fusion rates, a low incidence of reoperation and effective symptom relief in a "real world" setting among a large group of patients with refractory symptomatic disc degeneration.

Open Versus Minimally Invasive Fixation Techniques for Thoracolumbar Trauma: A Meta-Analysis

Study Design Systematic literature review and meta-analysis of studies published in English. Objective This study evaluated differences in outcome variables between percutaneous and open pedicle screws for traumatic thoracolumbar fractures. Methods A systematic review of PubMed, Cochrane, and Embase was performed. The variables of interest included postoperative visual analog scale (VAS) pain score, kyphosis angle, and vertebral body height, as well as intraoperative blood loss and operative time. The results were pooled by calculating the effect size based on the standardized difference in means. The studies were weighted by the inverse of the variance, which included both within- and between-study error. Confidence intervals were reported at 95%. Heterogeneity was assessed using the Q statistic and I (2). Results After two-reviewer assessment, 38 studies were eliminated. Six studies were found to meet inclusion criteria and were included in the meta-analysis. The combined effect size was found to be in favor of percutaneous fixation for blood loss and operative time (p < 0.05); however, there were no differences in vertebral body height (VBH), kyphosis angle, or VAS scores between open and percutaneous fixation. All of the studies demonstrated relative homogeneity, with I (2) < 25. Conclusions Patients with thoracolumbar fractures can be effectively managed with percutaneous or open pedicle screw placement. There are no differences in VBH, kyphosis angle, or VAS between the two groups. Blood loss and operative time were decreased in the percutaneous group, which may represent a potential benefit, particularly in the polytraumatized patient. All variables in this study demonstrated near-perfect homogeneity, and the effect is likely close to the true effect.

Sacral spinous processes: a morphologic classification and biomechanical characterization of strength

BACKGROUND

There has been increasing interest in using the lumbosacral spinous processes for fixation as a less invasive alternative to transpedicular instrumentation. Alhough prior studies have described the appearance and biomechanics of lumbar spinous processes, few have evaluated the dimensions, morphology, or strength of the sacral spinous processes.

PURPOSE

The goals of this study were to characterize the morphology of the S1 spinous process and biomechanical strength of the S1 spinous process when loaded in a cranial direction.

STUDY DESIGN

This study was performed as both an analysis of radiographic data and biomechanical testing of cadaveric specimens.

METHODS

Lumbosacral spine radiographs and computed tomography scans of 20 patients were evaluated for visibility and morphology of the S1 spinous process. S1 spinous process length, height, and size of the L5-S1 segment were measured. Additionally, 13 cadaveric lumbosacral spinal segments were obtained for biomechanical testing and morphologic analysis. Specimens were loaded at the S1 spinous process in a cranial direction via a strap, simulating resistance to a flexion moment applied across the L5-S1 segment. Peak load to failure, displacement, and mode of failure were recorded.

RESULTS

The S1 spinous process was clearly visible on lateral radiographs in only 10% of patients. Mean spinous process length (anterior-posterior) was 11.6 mm while mean spinous process height (cranial-caudal) was 23.1 mm. We identified six different morphologic subtypes of the S1 spinous process: fin, lumbar type, fenestrated, fused, tubercle, and spina bifida occulta. During tension loading of the S1 spinous process in the cephalad direction, mean peak load to failure was 439N, with 92% of specimens failing by fracture through the spinous process.

CONCLUSIONS

This is the first study evaluating sacral spinous process morphology, visibility, and biomechanical strength for potential instrumentation. Compared with lumbar spinous processes, sacral spinous processes are smaller with more variable morphology but have similar peak load to failure. For ideal visualization of morphology and suitability for interspinous fixation,preoperative three-dimensional imaging may be a valuable tool over plain radiographs.

Analysis of risk factors for adjacent superior vertebral pedicle-induced facet joint violation during the minimally invasive surgery transforaminal lumbar interbody fusion: a retrospective study

BACKGROUND

The purpose was to explore possible risk factors of facet joint violation induced by adjacent superior vertebral pedicle screw during the minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF).

METHODS

A total of 69 patients with lumbar degenerative disease, who underwent MIS-TLIF were retrospectively reviewed. Postoperative computed tomography images were used to assess the facet joint violation. The correlation of facet joint violations with gender, age, body mass index (BMI), the adjacent superior vertebral level, fusion segment numbers, position of screw insertion, straight leg-raising test (SLRT) results, clinical diseases and renal dysfunction were analyzed by Chi-square tests and binary logistic regression analysis.

RESULTS

The incidence of adjacent superior facet joint violations was 25.4 %. Chi-square test showed the patients with age <60 and high BMI (≥30 kg/m(2)) were more prone to have facet joint violations (P = 0.007; P = 0.006). The single segment fusion presented more facet joint violations than the double segments fusion (P = 0.048). The vertebral pedicle screw implant location at L5 showed more facet joint violations compared with that at L3 and L4 (P = 0.035). No correlation was found between gender, screw implant position, SLRT results, clinical diseases and renal dysfunction and facet joint violations. Logistic regression analysis revealed that age <60 years (OR: 2.902; 95 % CI 1.227-6.864; P = 0.015) and BMI ≥30 kg/m(2) (OR: 2.825; 95 % CI 1.191-6.700; P = 0.018 < 0.05) were significantly associated with facet joint violation.

CONCLUSION

These results found a high incidence of adjacent superior vertebral facet joint violation in the MIS-TLIF. Age <60 and BMI ≥30 kg/m(2) might be risk factors of facet joint violation. Evidence level: Level 4.