Accuracy of pedicle screw placement in the lumbosacral spine using conventional technique: computed tomography postoperative assessment in 102 consecutive patients

Three-Dimensional Fluoroscopic System to Assess Robotically Placed Pedicle Screws: Should We Confirm Robotic Pedicle Screw Placement With Advanced Imaging?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The purpose of this study is to determine the utility of advanced imaging to confirm the placement of robotic pedicle screws.

SUMMARY OF BACKGROUND DATA

With increasing robotic adoption, certain institutions and surgeons have developed protocols for obtaining 3D intraoperative imaging after robotic pedicle screw placement to ensure proper hardware placement. No studies have assessed the utility of these protocols relative to the potential risks of increased radiation exposure and operative time. The purpose of this study is to determine if we should be obtaining advanced imaging to confirm the placement of robotic pedicle screws.

METHODS

This is a single institution retrospective cohort study of patients from May 2022 to July 2023 who underwent lumbar spinal fusion by a high-volume orthopedic spine surgeon at a level 1 metropolitan hospital. All cases used combined robotics and navigation systems for pedicle screw placement and intraoperative 3D imaging for evaluation of screw position. Pedicle screw accuracy was assessed using the Gertzbein and Robbins system (GRS). Acceptable pedicle screw position was defined as GRS A or B.

RESULTS

Seventy patients with 354 robotically placed pedicle screws were assessed with intraoperative 3D fluoroscopy. All pedicle screws were placed in either a GRS type A or type B position. Three hundred forty-seven were placed in a GRS A classification (99.2%, 351/354), and 3 were placed in a GRS B classification (0.08% 3/354). No patients had screw-related complications. The average radiation dosage of 3D imaging was 289.7±164.6 mGy.

CONCLUSION

The robotic system places pedicle screws accurately without 3D intraoperative imaging. Given the increased radiation and operative time associated with 3D imaging protocols 3D imaging scans should only be obtained in cases with heightened clinical concern.

LEVEL OF EVIDENCE

Level IV.

O-arm navigation without apnoea in thoracolumbar and lumbar spine surgery: Outcomes and considerations in a prospective study

Background

Intra operative three dimensional navigation-assisted pedicle screw insertion typically requires apnoea for reliable image production. However this carries potential risks to the physiologically compromised patients such as patients having COPD, obesity, cardiac illnesses, and anaemia. In such patients' safe apnoea time may be as low as 1 min, and can cause life threatening complications. Therefore, this study was done to evaluate the accuracy of thoracolumbar and lumbar pedicle screw insertion using O-arm without using apnoea during imaging, to prevent such possible complications.

Methods

This is a single centre prospective study of 238 patients treated with pedicle screw implantation under O-arm guidance, without using apnoea while imaging. The pedicle breach rate during screw insertion was graded on Gertzbein classification. Also, two senior spine surgeons independently evaluated motion artifacts in the intra operative images and rated them as 'Significant' or 'Non-Significant' for the procedure. Values of p < 0.05 were considered statistically significant.

Results

Despite not using apnoea in 238 patients with 1120 screws, there were nil screw related complications. Only in one paediatric case of dorsal spine deformity, there were blurred and inaccurate images because of chest expansion, without apnoea. Hence he was given apnoea to render the image reliable for pedicle screw insertion. The screw placement in the pedicles was checked intraoperatively and graded for breach. Grade 2 breach were seen in only 2 cases (n = 3 screws) which were revised intra operatively. The interobserver agreement on motion artifacts was good (κ = 0.565, p < 0.001).

Conclusions

The results of pedicular screw insertion performed without induced apnea are comparable to those achieved with apnea when using O-arm imaging. This technique has proven to be a safe and reliable method for pedicle screw insertion in the thoracolumbar and lumbar spine, potentially mitigating physiological complications. Nonetheless, even minor motion artifacts, on the order of a few millimeters, can significantly impact outcomes in the cervical and upper thoracic spine. Therefore, further research is warranted to evaluate the efficacy and safety of this approach in these regions of the spine.

Comparative efficacy of robotic-assisted and freehand techniques for pedicle screw placement in spinal disorders: a meta-analysis and systematic review

The efficacy and safety of robotic-assisted pedicle screw placement compared to traditional fluoroscopy-guided techniques are of great interest in the field of spinal surgery. This systematic review and meta-analysis aimed to compare the outcomes of these two methods in patients with spinal diseases. Following the PRISMA guidelines, we conducted a systematic search across PubMed, Embase, Web of Science, and Cochrane Library. We included randomized controlled trials comparing robotic-assisted and fluoroscopy-guided pedicle screw placement in patients with spinal diseases. Outcome measures included the accuracy of pedicle screw placement, postoperative complication rates, intraoperative radiation exposure time, and duration of surgery. Data were analyzed using Stata software. Our analysis included 12 studies. It revealed significantly higher accuracy in pedicle screw placement with robotic assistance (odds ratio [OR] = 2.83, 95% confidence interval [CI] = 2.20-3.64, P < 0.01). Postoperative complication rates, intraoperative radiation exposure time, and duration of surgery were similar between the two techniques (OR = 0.72, 95% CI = 0.31 to 1.68, P = 0.56 for complication rates; weighted mean difference [WMD] = - 0.13, 95% CI = - 0.93 to 0.68, P = 0.86 for radiation exposure time; WMD = 0.30, 95% CI = - 0.06 to 0.66, P = 0.06 for duration of surgery). Robotic-assisted pedicle screw placement offers superior placement accuracy compared to fluoroscopy-guided techniques. Postoperative complication rates, intraoperative radiation exposure time, and duration of surgery were comparable for both methods. Future studies should explore the potential for fewer complications with the robotic-assisted approach as suggested by the lower point estimate.

100 Complex posterior spinal fusion cases performed with robotic instrumentation

Robotic navigation has been shown to increase precision, accuracy, and safety during spinal reconstructive procedures. There is a paucity of literature describing the best techniques for robotic-assisted spine surgery for complex, multilevel cases or in cases of significant deformity correction. We present a case series of 100 consecutive multilevel posterior spinal fusion procedures performed for multilevel spinal disease and/or deformity correction. 100 consecutive posterior spinal fusions were performed for multilevel disease and/or deformity correction utilizing robotic-assisted placement of pedicle screws. The primary outcome was surgery-related failure, which was defined as hardware breakage or reoperation with removal of hardware. A total of 100 consecutive patients met inclusion criteria. Among cases included, 31 were revision surgeries with existing hardware in place. The mean number of levels fused was 5.6, the mean operative time was 303 min, and the mean estimated blood loss was 469 mL. 28 cases included robotic-assisted placement of S2 alar-iliac (S2AI) screws. In total, 1043 pedicle screws and 53 S2AI screws were placed with robotic-assistance. The failure rate using survivorship analysis was 18/1043 (1.7%) and the failure rate of S2AI screws using survivorship analysis was 3/53 (5.7%). Four patients developed postoperative wound infections requiring irrigation and debridement procedures. None of the 1043 pedicle screws nor the 53 S2AI screws required reoperation due to malpositioning or suboptimal placement. This case series of 100 multilevel posterior spinal fusion procedures demonstrates promising results with low failure rates. With 1043 pedicle screws and 53 S2AI screws, we report low failure rates of 1.7% and 5.7%, respectively with zero cases of screw malpositioning. Robotic screw placement allows for accurate screw placement with no increased rate of postoperative infection compared to historical controls. Level of evidence: IV, Retrospective review.

Clinical Significance of Lateral Pedicle Screw Malposition in Lumbar Spine Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Our objective was to determine whether lateral pedicle screw breach affects fusion rates and patient-reported outcomes in lumbar fusion surgery.

SUMMARY OF BACKGROUND DATA

Although lateral pedicle screw malposition is considered relatively benign, few studies have focused specifically on clinical outcomes or fusion rates associated with lateral screw malposition.

METHODS

Twelve-month postoperative computed tomography scans were reviewed for lateral breach, severity of breach, and fusion status. Patients with lateral breach were compared with patients with no breach. Outcome measures included Numerical Pain Rating Scale for back and leg pain, Oswestry Disability Index, and SF-36 physical function (SF-36 PF). Multivariable linear and logistic regression and were adjusted for age, procedure, level, and/or baseline pain score.

RESULTS

Forty-five patients (31%) demonstrated 1 or more lateral breaches as compared with 99 patients without breach. After adjusting for baseline scores and fusion level, patients with 2 or more screw breaches experienced SF-36 PF score improvements that were 3.43 points less ( P =0.016) than patients with no lateral breach. After adjusting for baseline Numerical Pain Rating Scale, there was also a significant decrease in the odds of achieving minimally clinical important difference in back pain relief in these patients. There was no observed effect of lateral breach on the odds of successful fusion.

CONCLUSIONS

The current study did not observe an association between laterally malpositioned pedicle screws and nonunion. However, results are consistent with a negative effect on SF-36 PF scores and self-reported back pain at 12 months.

Augmented or Mixed Reality Enhanced Head-Mounted Display Navigation for In Vivo Spine Surgery: A Systematic Review of Clinical Outcomes

BACKGROUND

This research paper provides a systematic literature review (SLR) on the current status of augmented-reality head-mounted devices (AR-HMDs) that guide and navigate spine surgeries and pedicle screw placement.

METHODS

Embase, Scopus, PubMed, Cochrane Library and IEEE Xplore databases were screened for the systematic literature search to collect and statistically analyze live patient clinical, procedural and user experience data. Multi-level Poisson and binominal models were used for analysis.

RESULTS

In vivo patient data, only the clinically widely used Gertzbein-Robbins Scale, were published as an outcome in the recent heterogeneous literature. The statistical analysis supports the hypothesis that using AR-HMDs has the same clinical outcomes as using more expensive robot-assisted surgical (RAS) systems.

CONCLUSIONS

AR-HMD-guided pedicle screw insertion is reaching its technology readiness, providing similar benefits to RAS. Further meta-analysis is expected in the future from higher case-numbered and standardized randomized clinical trials.

Accuracy and Safety of Fluoroscopy-Assisted Transpedicular Screw Insertion in Thoracolumbar Spine Surgery: Evaluation of 122 Screws

The objective of this study is to determine the accuracy and safety of trans-pedicular screws' insertion in the thoracolumbar spine using a fluoroscopy-assisted surgical technique. We retrospectively evaluated all patients who underwent a postoperative computed tomography scan to assess the location of the pedicular screws following thoracolumbar spinal surgery, at the Mohammed Vth Military Training Hospital-Rabat, from January 2020 to April 2022. We used Gertzbein's classification to grade pedicular cortex breaches. A screw penetration greater than 4 mm (grades D–E) was considered critical and one less than 4 mm was classified as noncritical (grades A–C). A total of 122 screws inserted in the T1 to L5 vertebrae were included from 25 patients. The average age was 46 years old. Pathologies included degenerative disorders (5 patients), tumors (8 patients), and trauma (12 patients). All screws were inserted using lateral and anteroposterior fluoroscopic guidance. A total of 11 transpedicular screws breaches were identified. The breaches incidence was significantly higher in thoracic pedicles (8 screws) than in lumbar pedicles (3 screws). Of these, three critical cases occurred in two patients and one of them required reintervention. The remaining eight exceedances were not critical and were closely monitored and followed up. Transpedicular screws fluoroscopy-assisted surgical fixation can be performed for the stabilization of the thoracolumbar spine with satisfactory safety and precision.

A Modified Method of Triggered Electromyography Monitoring in Minimally Invasive Spine Surgery: Comparison to Conventional Techniques and Correlation with Body Mass Index

PURPOSE

Conventional triggered electromyography (EMG) in percutaneous pedicle screw (PPS) systems may be unreliable due to the interaction between the insertion apparatus and patient's soft tissue. Our aim was 1) to describe a modified technique of triggered EMG monitoring using insulated Kirschner wire (K-wires), 2) to compare EMG potentials with conventional techniques, and 3) to demonstrate the relationship between patient body mass index (BMI) and triggered EMG potentials.

METHODS

This was a prospective cross-sectional study of 50 patients undergoing minimally invasive PPS placement. Triggered EMG measurements using K-wires before and after insulation were compared. The difference between EMG measurements before and after insulation was correlated with patient BMI.

RESULTS

A total of 50 patients, 22 females and 28 males, underwent triggered EMG testing using K-wires prior to final PPS placement in the thoracic and lumbosacral spine for a total of 472 triggered EMG measurements. When compared to standard triggered EMG monitoring, insulated triggered EMG monitoring demonstrated an average 55.4% decrease in EMG values (P < 0.001). Increasing BMI correlated to increasing % decrease in EMG values (r-coefficient, 0.376; P < 0.01).

CONCLUSIONS

We describe a cost-effective, efficient, and reliable technique for triggered EMG during PPS placement which may help ensure accurate screw placement and minimize potentially devastating complications.

A New Interlaminar/Interspinous and Facet-Joint Stabilization System in Lumbar Degenerative Disk Disease: 2 Years of Results

INTRODUCTION

In lumbar degenerative disk diseases (DDDs), we include a wide range of lumbar pathologies. Lumbar spinal stenosis with or without spondylolisthesis is a common cause of lower-limb pain in elderly patients. The surgical treatment of lumbar DDD consists of the decompression of the neural structures or the decompression and fusion of the involved motion segment. Unfortunately, rigid spinal implants followed by fusion cause increased stresses on the neighboring spinal segments, often leading to adjacent segment degeneration. The aim of this paper is to present a new system for interlaminar/interspinous and facet-joint stabilization and fusion.

MATERIAL AND METHODS

From March 2018 to June 2021, 175 patients with severe lumbar back and/or leg pain were operated on with this device after the failure of conservative treatment for a minimum of 6 months. For this study, we considered 75 available patients with a minimum follow-up time of 24 months. Patients rated their back pain and leg pain on a visual analog scale (VAS) after surgery and at the last follow-up; also, the postoperative consumption of analgesic drugs was investigated. Finally, patients were asked whether they would undergo this kind of surgery again or recommend it. The device is designed to promote a better and more efficient intervertebral fusion: Bone Ingrowth technology allows the system to achieve the best response from the bone tissue.

RESULTS

All procedures were performed without any complications. A reoperation was required in five cases (6.7%) because of implant failure. In one case, a spinous process and unilateral articular process fracture occurred. In four cases, a subcutaneous ISCHIA (one case) or FILICUDI (three cases) pullout was observed. Significant improvements following lumbar surgery were observed when evaluating the postoperative VAS values, analgesic drug consumption levels, and patients' satisfaction ratings. Evident fusion was seen in 58 of 75 patients (77.3%).

CONCLUSIONS

Our interspinous/interlaminar and facet-joint implant solution, associated with bone grafting, provided vertebral fusion in most stenotic patients with Grade I DS undergoing bilateral microdecompression (BMD) or bilateral decompression via the unilateral approach (BDUA). A higher number of patients and a longer follow-up will certainly be required to completely validate these new devices, but this minimally invasive surgery (MIS) is currently very encouraging and satisfactory.

X23D-Intraoperative 3D Lumbar Spine Shape Reconstruction Based on Sparse Multi-View X-ray Data

Visual assessment based on intraoperative 2D X-rays remains the predominant aid for intraoperative decision-making, surgical guidance, and error prevention. However, correctly assessing the 3D shape of complex anatomies, such as the spine, based on planar fluoroscopic images remains a challenge even for experienced surgeons. This work proposes a novel deep learning-based method to intraoperatively estimate the 3D shape of patients' lumbar vertebrae directly from sparse, multi-view X-ray data. High-quality and accurate 3D reconstructions were achieved with a learned multi-view stereo machine approach capable of incorporating the X-ray calibration parameters in the neural network. This strategy allowed a priori knowledge of the spinal shape to be acquired while preserving patient specificity and achieving a higher accuracy compared to the state of the art. Our method was trained and evaluated on 17,420 fluoroscopy images that were digitally reconstructed from the public CTSpine1K dataset. As evaluated by unseen data, we achieved an 88% average F1 score and a 71% surface score. Furthermore, by utilizing the calibration parameters of the input X-rays, our method outperformed a counterpart method in the state of the art by 22% in terms of surface score. This increase in accuracy opens new possibilities for surgical navigation and intraoperative decision-making solely based on intraoperative data, especially in surgical applications where the acquisition of 3D image data is not part of the standard clinical workflow.

CT-Navigated Spinal Instrumentations-Three-Dimensional Evaluation of Screw Placement Accuracy in Relation to a Screw Trajectory Plan

Background and Objectives: In the literature, spinal navigation and robot-assisted surgery improved screw placement accuracy, but the majority of studies only qualitatively report on screw positioning within the vertebra. We sought to evaluate screw placement accuracy in relation to a preoperative trajectory plan by three-dimensional quantification to elucidate technical benefits of navigation for lumbar pedicle screws. Materials and Methods: In 27 CT-navigated instrumentations for degenerative disease, a dedicated intraoperative 3D-trajectory plan was created for all screws. Final screw positions were defined on postoperative CT. Trajectory plans and final screw positions were co-registered and quantitatively compared computing minimal absolute differences (MAD) of screw head and tip points (mm) and screw axis (degree) in 3D-space, respectively. Differences were evaluated with consideration of the navigation target registration error. Clinical acceptability of screws was evaluated using the Gertzbein−Robbins (GR) classification. Results: Data included 140 screws covering levels L1-S1. While screw placement was clinically acceptable in all cases (GR grade A and B in 112 (80%) and 28 (20%) cases, respectively), implanted screws showed considerable deviation compared to the trajectory plan: Mean axis deviation was 6.3° ± 3.6°, screw head and tip points showed mean MAD of 5.2 ± 2.4 mm and 5.5 ± 2.7 mm, respectively. Deviations significantly exceeded the mean navigation registration error of 0.87 ± 0.22 mm (p < 0.001). Conclusions: Screw placement was clinically acceptable in all screws after navigated placement but nevertheless, considerable deviation in implanted screws was noted compared to the initial trajectory plan. Our data provides a 3D-quantitative benchmark for screw accuracy achievable by CT-navigation in routine spine surgery and suggests a framework for objective comparison of screw outcome after navigated or robot-assisted procedures. Factors contributing to screw deviations should be considered to assure optimal surgical results when applying navigation for spinal instrumentation.

Comparison of pedicle screw placement accuracy between two types of imaging support (Artis Zeego versus two-dimensional fluoroscopy): a cross-sectional observational study

Background

The pedicle screw system is widely used in spine surgery, and it provides rigid fixation and leads to successful subsequent deformity correction and bony fusion. The standard imaging technique for pedicle screw insertion is two-dimensional images obtained from C-arm-type X-ray fluoroscopy. Artis Zeego is an emerging intraoperative imaging technique that can provide conventional two-dimensional fluoroscopic images and rapid three-dimensional fluoroscopic computed tomography reconstruction imaging. The aim of this study is to compare the insertion accuracies of PS placement using Artis Zeego and conventional 2D X-ray fluoroscopy.

Methods

In this study, we retrospectively reviewed the postoperative images of thoracolumbar fusion patients who underwent surgery using pedicle screws between 2013 and 2018. Pedicle screw malplacement was assessed using a four-grade classification by Rao et al. Misplacement rates were compared between pedicle screws assisted with Artis Zeego and two-dimensional fluoroscopy.

Results

A total of 1107 pedicle screws in 153 patients were inserted using Artis Zeego, and 427 pedicle screws in 80 patients were inserted using fluoroscopy. The overall perforation rate was 4.2% (46 perforations of 1106 pedicle screws) in the Artis Zeego group and 7.7% (33 perforations of 427 pedicle screws) in the fluoroscopy group. In the Artis Zeego group, 43 (3.9%) screws were classified as grade 1, and three (0.3%) screws were classified as grade 2. In the fluoroscopy group, 21 (4.9%) screws were classified as grade 1, 10 (2.3%) screws were classified as grade 2, and 2 (0.5%) screws were classified as grade 3. The use of Artis Zeego was associated with a significantly lower screw malplacement rate than was the use of fluoroscopy (p < 0.001).

Conclusions

Our results demonstrated that pedicle screw placement with Artis Zeego was associated with a lower malplacement rate than was conventional two-dimensional fluoroscopy. No severe malplacement was observed in the Artis Zeego group. Thus, Artis Zeego could be a good option for improving pedicle screw accuracy.

Sacral Insufficiency Fracture Following Short-Segment Lumbosacral Fusion: Case Series and Review of the Literature

STUDY DESIGN

Retrospective case series.

OBJECTIVE

Sacral insufficiency fracture is a rare and serious complication following lumbar spine instrumented fusion. The purpose of this study was to describe the patient characteristics, presentation, evaluation, treatment options, and outcomes for patients with sacral insufficiency fracture after short-segment lumbosacral fusion.

METHODS

Six patients from our institutional database and 16 patients from literature review were identified with a sacral insufficiency fracture after short-segment (L4-S1 or L5-S1) lumbar fusion within 1 year of surgery.

RESULTS

Patients were 55% female with a mean age of 58 years and body mass index of 30 kg/m². Osteoporosis or osteopenia was the most common comorbidity (85%). Half of patients sustained a sacral fracture after surgery from a posterior approach, while the others had anterior or anterior-posterior surgery. Mean time to fracture was 42 days with patients clinically presenting with new sacral pain (86%), radiculopathy (60%), or neurologic deficit (5%). Ultimately, 73% of patients underwent operative fixation often involving extension of the construct (75%) and fusion to the pelvis (69%). Men (P = .02) and patients with new radicular pain or neurologic deficit (P = .01) were more likely to undergo revision surgical treatment while women over 50 years of age were more likely to be treated conservatively (P = .003).

CONCLUSIONS

Spine surgeons should monitor for sacral insufficiency fracture as a source of new-onset pain in the postoperative period in patients with a short segment fusion to the sacrum. The recognition of this complication should prompt an assessment of bone health and management of underlying bone fragility.

Evaluation of the implantation of transpedicular screws in spinal instrumentation with free-hand technique and navigation-assisted with intraoperative computed tomography: An analytical-positional study

BACKGROUND

Spinal instrumentation using transpedicular screws has been used for decades to stabilize the spine. In October 2018, an intraoperative CT system was acquired in the Neurosurgery service of the University Hospital Complex of Vigo, this being the first model of these characteristics in the Spanish Public Health System, so we began a study from January 2015 to December 2019 to assess the precision of the transpedicular screws implanted with this system compared with a control group performed with the classical technique and final fluoroscopic control.

METHODS

The study was carried out in patients who required transpedicular instrumentation surgery, in total 655 screws were placed, 339 using the free-hand technique (Group A) and 316 assisted with intraoperative CT navigation (Group B) (p>0.05). Demographic characteristics, related to surgery and the screw implantation grades were assessed using the Gertzbein-Robbins classification.

RESULTS

92 patients were evaluated, between 12 and 86 years (average: 57.1 years). 161 thoracic screws (24.6%) and 494 lumbo-sacral screws (75.4%) were implanted. Of the thoracic screws, 33 produced a pedicle rupture. For the lumbo-sacral screws, 71 have had pedicle violation. The overall correct positioning rate for the free-hand group was 72.6% and for the CT group it was 96.5% (p<0.05).

CONCLUSION

The accuracy rate is higher in thoracic-lumbar instrumentation in the navigation group versus free-hand group with fluoroscopic control.

Intraoperative Computed Tomography for C1-C2 Stabilization by Goel-Harms: Analysis of Clinical Efficacy and a Novel Classification of Screw Placement Accuracy

BACKGROUND

The introduction of intraoperative computed tomography (iCT) could improve the surgical results of C1-C2 stabilization by Goel-Harms, especially in patients with complex deformities. This study aims to investigate the impact of iCT on the accuracy of C1-C2 screw positioning and to develop a score based on multiparametric analysis of imaging data (Cervical Screw Placement Accuracy score [CSPAs]).

METHODS

Twenty-one patients were retrospectively evaluated. The data obtained with the use of an iCT were compared with the incidence of cases of malpositioning in the literature. Multiparametric imaging criteria were developed: the 82 screw positions were evaluated using the CSPA criteria and 2 additional variables. The CSPAs was obtained from the aggregation of the CSPAs criteria: optimal (CSPAs ≥8), suboptimal (CSPAs = 6-7), malpositioned (CSPAs ≤5).

RESULTS

The average incidence of malpositioning in C1-C2 arthrodesis decreased from 13% without iCT to 1.2% with the aid of iCT, considering a monoparametric value. The CSPAs analysis shows a greater discretion and higher number of well-defined categories of the accuracy of C1-C2 screw position: optimal, 80.3%; suboptimal, 17.1%; and malposition, 2.6%. A correlation was observed between the accuracy of the positioning of both right and left screws in C2. Furthermore, the anatomic site of C2 screws was found to be a predictor of cortical invasion.

CONCLUSIONS

The results suggest that the introduction of the iCT is associated with a consistent improvement of the accuracy in the positioning of the screws. A multiparametric score (CSPAs) could improve the assessment of screw placement.

The Clinical Impact of Image Guidance and Robotics in Spinal Surgery: A Review of Safety, Accuracy, Efficiency, and Complication Reduction

Image guidance (IG) and robotic-assisted (RA) surgery are modern technological advancements that have provided novel ways to perform precise and accurate spinal surgery. These innovations supply real-time, three-dimensional imaging information to aid in instrumentation, decompression, and implant placement. Although nothing can replace the knowledge and expertise of an experienced spine surgeon, these platforms do have the potential to supplement the individual surgeon's capabilities. Specific advantages include more precise pedicle screw placement, minimally invasive surgery with less reliance on intraoperative fluoroscopy, and lower radiation exposure to the surgeon and staff. As these technologies have become more widely adopted over the years, novel uses such as tumor resection have been explored. Disadvantages include the cost of implementing IG and robotics platforms, the initial learning curve for both the surgeon and the staff, and increased patient radiation exposure in scoliosis surgery. Also, given the relatively recent transition of many procedures from inpatient settings to ambulatory surgery centers, access to current devices may be cost prohibitive and not as readily available at some centers. Regarding patient-related outcomes, much further research is warranted. The short-term benefits of minimally invasive surgery often bolster the perioperative and early postoperative outcomes in many retrospective studies on IG and RA surgery. Randomized controlled trials limiting such confounding factors are warranted to definitively show potential independent improvements in patient-related outcomes specifically attributable to IG and RA alone. Nonetheless, irrespective of these current unknowns, it is clear that these technologies have changed the field and the practice of spine surgery. Surgeons should be familiar with the potential benefits and tradeoffs of these platforms when considering adopting IG and robotics in their practices.

L5 nerve root injury caused by anterolateral malpositioning of loosened S1 pedicle screws: illustrative cases

BACKGROUND

Although malpositioning of pedicle screws into the spinal canal and intervertebral foramen can cause spinal nerve root injuries, there are few reports of L5 nerve root injuries when S1 pedicle screws have been inserted anterolaterally. The authors report two cases of L5 nerve root injury caused by anterolateral malpositioning of loosened S1 pedicle screws.

OBSERVATIONS

In both patients, S1 pedicle screws were inserted toward the outside of the S1 anterior foramen, and the tip of the screws perforated the anterior sacral cortex. L5 nerve root impairment was not observed immediately after surgery. However, severe leg pain in the L5 area was observed after the S1 pedicle screws became loosened. In case 1, the symptoms could not be controlled with conservative treatment. Reoperation was performed 3 months after the initial surgery. In case 2, the symptoms gradually improved with conservative treatment because the area around the loosened S1 screw was surrounded by newly formed bone that stabilized the screws, as observed with computed tomography 1 year after surgery.

LESSONS

Surgeons should recognize that anterolateral malpositioning of S1 pedicle screws can cause L5 nerve root injury. The screws should be inserted in the correct direction without loosening.

Machine Vision Navigation in Spine Surgery

The advancements in computing and digital localizer technologies has led to the evolving clinical application of image-guided technology for the surgical management of spinal disorders. Image-guided spinal navigation addresses the limitations of fluoroscopy and improves the accurate placement of fixation screws. Several navigation platforms are currently available, each having its own unique advantages and disadvantages. The most recent spinal navigation system developed utilizes machine vision structured light imaging which creates a precise and detailed three-dimensional image of the exposed surface anatomy and co-registers it to a pre-operatively or intra-operatively acquired image. This system improves upon the intraoperative workflow and efficiency of the navigation process. With the continued advancements in machine vision, there is a potential for clinical applications that extend beyond surgical navigation. These applications include reducing the potential for wrong level spine surgery and providing for real-time tracking of spinal deformity correction. As the adoption and clinical experience with navigation continues to expand and evolve, the technology that enables navigation also continues to evolve.

Evaluation of the implantation of transpedicular screws in spinal instrumentation with free-hand technique and navigation-assisted with intraoperative computed tomography: An analytical-positional study

BACKGROUND

Spinal instrumentation using transpedicular screws has been used for decades to stabilize the spine. In October 2018, an intraoperative CT system was acquired in the Neurosurgery service of the University Hospital Complex of Vigo, this being the first model of these characteristics in the Spanish Public Health System, so we began a study from January 2015 to December 2019 to assess the precision of the transpedicular screws implanted with this system compared with a control group performed with the classical technique and final fluoroscopic control.

METHODS

The study was carried out in patients who required transpedicular instrumentation surgery, in total 655 screws were placed, 339 using the free-hand technique (Group A) and 316 assisted with intraoperative CT navigation (Group B) (p>0.05). Demographic characteristics, related to surgery and the screw implantation grades were assessed using the Gertzbein-Robbins classification.

RESULTS

92 patients were evaluated, between 12 and 86 years (average: 57.1 years). 161 thoracic screws (24.6%) and 494 lumbo-sacral screws (75.4%) were implanted. Of the thoracic screws, 33 produced a pedicle rupture. For the lumbo-sacral screws, 71 have had pedicle violation. The overall correct positioning rate for the free-hand group was 72.6% and for the CT group it was 96.5% (p<0.05).

CONCLUSION

The accuracy rate is higher in thoracic-lumbar instrumentation in the navigation group versus free-hand group with fluoroscopic control.

Long-length tomosynthesis and 3D-2D registration for intraoperative assessment of spine instrumentation

PURPOSE

A system for long-length intraoperative imaging is reported based on longitudinal motion of an O-arm gantry featuring a multi-slot collimator. We assess the utility of long-length tomosynthesis and the geometric accuracy of 3D image registration for surgical guidance and evaluation of long spinal constructs.

METHODS

A multi-slot collimator with tilted apertures was integrated into an O-arm system for long-length imaging. The multi-slot projective geometry leads to slight view disparity in both long-length projection images (referred to as 'line scans') and tomosynthesis 'slot reconstructions' produced using a weighted-backprojection method. The radiation dose for long-length imaging was measured, and the utility of long-length, intraoperative tomosynthesis was evaluated in phantom and cadaver studies. Leveraging the depth resolution provided by parallax views, an algorithm for 3D-2D registration of the patient and surgical devices was adapted for registration with line scans and slot reconstructions. Registration performance using single-plane or dual-plane long-length images was evaluated and compared to registration accuracy achieved using standard dual-plane radiographs.

RESULTS

Longitudinal coverage of ∼50-64 cm was achieved with a single long-length slot scan, providing a field-of-view (FOV) up to (40 × 64) cm², depending on patient positioning. The dose-area product (reference point air kerma × x-ray field area) for a slot scan ranged from ∼702-1757 mGy·cm², equivalent to ∼2.5 s of fluoroscopy and comparable to other long-length imaging systems. Long-length scanning produced high-resolution tomosynthesis reconstructions, covering ∼12-16 vertebral levels. 3D image registration using dual-plane slot reconstructions achieved median target registration error (TRE) of 1.2 mm and 0.6° in cadaver studies, outperforming registration to dual-plane line scans (TRE = 2.8 mm and 2.2°) and radiographs (TRE = 2.5 mm and 1.1°). 3D registration using single-plane slot reconstructions leveraged the ∼7-14° angular separation between slots to achieve median TRE ∼2 mm and <2° from a single scan.

CONCLUSION

The multi-slot configuration provided intraoperative visualization of long spine segments, facilitating target localization, assessment of global spinal alignment, and evaluation of long surgical constructs. 3D-2D registration to long-length tomosynthesis reconstructions yielded a promising means of guidance and verification with accuracy exceeding that of 3D-2D registration to conventional radiographs.

Three-dimensional distribution of CT attenuation in the lumbar spine pedicle wall

This study investigated in vivo the three-dimensional distribution of CT attenuation in the lumbar spine pedicle wall measured in Hounsfield Unit (HU). Seventy-five volunteers underwent clinical lumbar spine CT scans. Data was analyzed with custom-written software to determine the regional variation in pedicle wall attenuation values. A cylindrical coordinate system oriented along the pedicle's long axis was used to calculate the pedicular wall attenuation distribution three-dimensionally and the highest attenuation value was identified. The pedicular cross-section was divided into four quadrants: lateral, medial, cranial, and caudal. The mean HU value for each quadrant was calculated for all lumbar spine levels (L1-5). The pedicle wall attenuation was analyzed by gender, age, spinal levels and anatomical quadrant. The mean HU values of the pedicle wall at L1 and L5 were significantly lower than the values between L2-4 in both genders and in both age groups. Furthermore, the medial quadrant showed higher HU values than the lateral quadrant at all levels and the caudal quadrant showed higher HU values at L1-3 and lower HU values at L4-5 than the cranial quadrant. These findings may explain why there is a higher incidence of pedicle screw breach in the pedicle lateral wall.

Intraoperative image guidance for lateral position surgery

Recent advances in minimally invasive spine surgery techniques have precipitated the popularity of lateral position spine surgery, such as lateral lumbar interbody fusion (LLIF) and oblique lumbar interbody fusion (OLIF). Lateral position surgery offers a unique, minimally invasive approach to the lumbar spine that allows for preservation of anterior and posterior spinal elements. Traditionally, surgeons have relied upon fluoroscopy for triangulation and implant placement. Over the last decade, intraoperative 3-dimensional navigation (ION) has risen to the forefront of innovation in LLIF and OLIF. This technology utilizes intra-operative advanced imaging, such as comminuted tomography (CT), to map the patient’s 3D anatomy and allows the surgeon to accurately visualize instruments and implants in spatial relationship to the patient’s anatomy in real time. ION has the potential to improve accuracy during instrumentation, decrease operating room times, lower radiation exposure to the surgeon and staff, and increase feasibility of single-position surgery during which the spine is instrumented both laterally and posteriorly while the patient remains in the lateral decubitus position. Despite the advantages of ION, the intra-operative radiation exposure risk to patients is controversial. Future directions include continued innovation in ultra low radiation imaging (ULRI) techniques and image enhancement technology and in uses of robot-assisted navigation in single-position spine surgery.

Intraoperative cone beam computed tomography is as reliable as conventional computed tomography for identification of pedicle screw breach in thoracolumbar spine surgery

Objectives

To test the hypothesis that intraoperative cone beam computed tomography (CBCT) using the Allura augmented reality surgical navigation (ARSN) system in a dedicated hybrid operating room (OR) matches computed tomography (CT) for identification of pedicle screw breach during spine surgery.

Methods

Twenty patients treated with spinal fixation surgery (260 screws) underwent intraoperative CBCT as well as conventional postoperative CT scans (median 12 months after surgery) to identify and grade the degree of pedicle screw breach on both scan types, according to the Gertzbein grading scale. Blinded assessments were performed by three independent spine surgeons and the CT served as the standard of reference. Screws graded as Gertzbein 0 or 1 were considered clinically accurate while grades 2 or 3 were considered inaccurate. Sensitivity, specificity, and negative predictive value were the primary metrics of diagnostic performance.

Results

For this patient group, the negative predictive value of an intraoperative CBCT to rule out pedicle screw breach was 99.6% (CI 97.75–99.99%). Among 10 screws graded as inaccurate on CT, 9 were graded as such on the CBCT, giving a sensitivity of 90.0% (CI 55.5–99.75%). Among the 250 screws graded as accurate on CT, 244 were graded as such on the CBCT, giving a specificity of 97.6% (CI 94.85–99.11%).

Conclusions

CBCT, performed intraoperatively with the Allura ARSN system, is comparable and non-inferior to a conventional postoperative CT scan for ruling out misplaced pedicle screws in spinal deformity cases, eliminating the need for a postoperative CT.

Key Points

• Intraoperative cone beam computed tomography (CT) using the Allura ARSN is comparable with conventional CT for ruling out pedicle screw breaches after spinal fixation surgery.

• Intraoperative cone beam computed tomography can be used to assess need for revisions of pedicle screws making routine postoperative CT scans unnecessary.

• Using cone beam computed tomography, the specificity was 97.6% and the sensitivity was 90% for detecting pedicle screw breaches and the negative predictive value for ruling out a pedicle screw breach was 99.6%.

Accuracy of Thoracolumbar Pedicle Screw Insertion Based on Routine Use of Intraoperative Imaging and Navigation

Study Design

Retrospective review.

Purpose

To determine the accuracy of thoracolumbar pedicle screw insertion with the routine use of three-dimensional (3D) intraoperative imaging and navigation over a large series of screws in an Asian population.

Overview of Literature

The use of 3D intraoperative imaging and navigation in spinal surgery is aimed at improving the accuracy of pedicle screw insertion. This study analyzed 2,240 pedicle screws inserted with the routine use of intraoperative navigation. It is one of very few studies done on an Asian population with a large series of screws.

Methods

Patients who had undergone thoracolumbar pedicle screws insertion using intraoperative imaging and navigation between 2009 and 2017 were retrospectively analyzed. Computed tomography (CT) images acquired after the insertion of pedicle screws were analyzed for breach of the pedicle wall. The pedicle screw breaches were graded according to the Gertzbein classification. The breach rate and revision rate were subsequently calculated.

Results

A total of 2,240 thoracolumbar pedicle screws inserted under the guidance of intraoperative navigation were analyzed, and the accuracy of the insertion was 97.41%. The overall breach rate was 2.59%, the major breach rate was 0.94%, and the intraoperative screw revision rate was 0.7%. There was no incidence of return to the operating theater for revision of screws.

Conclusions

The routine use of 3D navigation and intraoperative CT imaging resulted in consistently accurate pedicle screw placement. This improved the safety of spinal instrumentation and helped in avoiding revision surgery for malpositioned screws.

Postoperative 320 multi-slice computed tomography in assessment of pedicle screw insertion in thoraco-lumbar fixation

Background

Pedicle screw instrumentation is used widely in lumbar spine for stabilization to enhance arthrodesis and has been accepted in the thoracic spine in recent years. The purpose of this study was to assess the value of postoperative 320 multi-slice computed tomography (MSCT) in assessment of pedicle screw placement in patients with spinal fixation with clinical and surgical correlation.

Results

A total of 340 pedicular screws were inserted to 70 cases. 286 (84.12%) were in, 54 screws (15.88%) were violated, and revision surgeries were required for 5 displaced screws. On axial, coronal reconstruction and three-dimensional (3D) reformatted CT images 36, 47, and 54 displaced screws were detected, respectively. Both sensitivity and specificity for 3D reformatted images were 100%. For axial image, they were 97.6% and 89.4%, respectively, compared with surgical findings in 5 revised screws.

Conclusion

Multi-slice CT scan is a valuable and valid postoperative assessment tool of accuracy of spinal pedicle screw placement.

Initial Single-Institution Experience With a Novel Robotic-Navigation System for Thoracolumbar Pedicle Screw and Pelvic Screw Placement With 643 Screws

BACKGROUND

Robotic-guided navigation systems for pedicle screw placement has gained recent interest to ensure accuracy and safety and diminish radiation exposure. There have been no published studies using a new combined robotics and navigation system (Globus ExcelsiusGPS system). The purpose of this study was to demonstrate safety with this system.

METHODS

This is a case series of consecutive patients at a single institution from February 1, 2018, to August 31, 2018. All patients who had planned placement of thoracic and lumbar pedicle screws using the combined robotics-navigation system were included. Chart review was performed for operative details. A subgroup analysis was performed on patients with postoperative computed tomography (CT) scans to assess screw placement accuracy using the Gertzbein and Robbins system. Acceptable pedicle screw position was defined as grade A or B.

RESULTS

One hundred six patients were included, with 636 pedicle screws, 6 iliac screws, and 1 S2AI screw. Five cases were aborted for technical issues. In the remaining 101 patients, 88 patients had screws placed using preoperative CT planning and 13 patients using intraoperative fluoroscopy planning. All screws except for 5 pedicle screws in 2 patients were placed successfully using the robot (99%). These 5 pedicle screws were placed by converting to a fluoro-guided technique without robotic assistance. Eighty-six patients had screws placed using a percutaneous technique, and 15 patients had screws placed using an open technique. Ninety-eight patients underwent interbody placement: 28 anterior lumbar interbody fusions (ALIFs), 12 lateral lumbar interbody fusions (LLIFs), and 58 transforaminal lumbar interbody fusions (TLIFs). All ALIFs and LLIFs were performed prior to placement of the screws. Four LIF patients had screws placed in the lateral position. No patients had screw-related complications intraoperatively or postoperatively, and no patients returned to the operating room for screw revision. Thirteen patients underwent postoperative CT for various reasons. Of the 66 pedicle screws that were examined with postoperative CT, all screws (100%) had acceptable position.

CONCLUSION

This study demonstrates that the combined robotics and navigation system is a novel technology that can be utilized to place pedicle screws and pelvic screws safely and has the potential to reduce screw-related complications.

LEVEL OF EVIDENCE

4 (case series).

Endoscopy-Assisted Diagnosis and Revision of a Malpositioned Screw

BACKGROUND

Pedicle screw insertion is a common procedure in spine surgery, and freehand, fluoroscopic, and robotic-assisted techniques all are used. These are indirect methods that use fluoroscopy, and direct visualization of canal involvement has not been possible. However, owing to the development of high-definition imaging modalities, delicate procedures that use endoscopy are possible.

CASE DESCRIPTION

A 47-year-old man presented with severe radiating pain in his leg after undergoing L5-S1 level endoscopic transforaminal lumbar interbody fusion and percutaneous pedicular screw fixation. The patient then underwent an endoscopy-assisted technique for violated spinal canal and screw revision in which the misplaced screw was directly visualized using endoscopy and the trajectory of the misplaced screw was changed. With 30° endoscopy, we directly visualized the screw thread and root compression. Then with 0° endoscopy, we changed the screw trajectory inside the pedicle with an anatomic landmark. The patient's radiating pain was completely relieved after revision of the malpositioned screw. Postoperative imaging showed the revised screw trajectory inside the pedicle.

CONCLUSIONS

Endoscopy-assisted pedicle screw insertion does not require an additional incision, and early recovery after the procedure is possible. Accurate diagnosis of canal pathology and treatment are possible with direct visualization using endoscopy.

Pedicle screw accuracy in clinical utilization of minimally invasive navigated robot-assisted spine surgery

In the emerging field of robot-assisted spine surgery, the radiographic evaluation of pedicle screw accuracy in clinical application is an area of high interest. This study describes the pedicle screw accuracy of the first 56 consecutive cases in which navigated robotic assistance was used in a private practice clinical setting. A retrospective, Institutional Review Board-exempt review of the first 56 navigated robot-assisted spine surgery cases was performed. Pedicle screw malposition, reposition, and return to operating room (OR) rates were collected. A CT-based Gertzbein and Robbins system (GRS) was used to classify pedicle screw accuracy. In the first 56 robotic cases, 356 total pedicle screws were placed. Eight screws were placed without the robot due to surgeon discretion. Of the 348 pedicle screws inserted by navigated robotic guidance, only 2.6% (9/348) were repositioned, resulting in a 97.4% (339/348) successful screw placement rate. The average age was 64, and 48% were female. Average body mass index was 31 kg/m². Based on the GRS CT-based grading, 97.7% (340/348) were graded A or B, 1.7% (6/348) screws were graded C, and only 0.6% (2/348) of screws were graded D. Two complications, explantation of interbody and vacuum-assisted wound closure, were reported as requiring a return to the OR, but these were not related to robotic guidance or pedicle screws. This study demonstrated a high level of accuracy (97.7%) in the first 56 cases using navigated, robot-assisted surgery based on the GRS. There were two non-screw-related complications requiring return to the operating room.

Noise-optimised virtual monoenergetic imaging of dual-energy CT: effect on metal artefact reduction in patients with lumbar internal fixation

PURPOSE

The purpose of this study was to evaluate the effects of noise-optimised virtual monoenergetic imaging (VMI+) reconstructions on reducing metal artefacts compared to traditional virtual monoenergetic imaging (VMI) and linearly blended (M_0.6) reconstructions in patients with lumbar metal internal fixation in dual-energy CT (DECT).

METHODS

Forty patients who underwent DECT were evaluated in this retrospective study. Images were reconstructed with M_0.6 and with VMI+ and VMI at 10-keV intervals from 40 keV to 190 keV. Attenuation and noise were measured in the hyperdense artefacts, hypodense artefacts, spinal canal, abdominal aorta (AA), and inferior vena cava (IVC). An artefact index (AI) was calculated. A subjective evaluation of the metal-bone interface, surrounding soft tissue, spinal canal, AA, and IVC was conducted.

RESULTS

The AI values for the hypodense artefacts, spinal canal, and IVC were lowest in the 130 keV VMI+ series, for the hyperdense artefacts in the 120 keV VMI+ series, and for the AA in the 190 keV VMI+ series. Except for the hypodense artefacts, the AI values were lower compared to the M_0.6 images and all the VMI series (all p < 0.05). The subjective image quality was highest at 130 keV VMI+ for the metal-bone interface, surrounding soft tissue, AA, and IVC, and at 120 keV VMI+ for the spinal canal. Except for the AA, these rating scores were higher compared to the M_0.6 images and the entire VMI series (all p < 0.05).

CONCLUSIONS

DECT with high-keV VMI+ efficiently reduces metal artefacts and shows superior image quality in patients with lumbar internal fixation. These slides can be retrieved from Electronic Supplementary Material.

Accuracy of Current Techniques for Placement of Pedicle Screws in the Spine: A Comprehensive Systematic Review and Meta-Analysis of 51,161 Screws

BACKGROUND

Pedicle screws (PSs) are routinely used for stabilization to enhance fusion in a variety of spinal diseases. Although the accuracy of different PS placement methods has been previously reported, most of these studies have been limited to 1 or 2 techniques. The purpose was to determine the current accuracy of PS placement among 4 modalities of PS insertion (freehand [FH], fluoroscopy-assisted [FA], computed tomography navigation-guided [CTNav], and robot-assisted [RA]) and analyze variables associated with screw misplacement.

METHODS

A systematic review was performed of peer-reviewed articles reporting PS accuracy of 1 technique from January 1990 to June 2018. Accuracy of PS placement, PS insertion technique, and pedicle breach (PB) data were collected. A meta-analysis was performed to estimate the overall pooled (OP) rates of PS accuracy as a primary outcome, stratified by screw insertion techniques. Potential determinants were analyzed via meta-regression analyses.

RESULTS

Seventy-eight studies with 7858 patients, 51,161 PSs, and 3614 cortical PBs were included. CTNav showed the highest PS placement accuracy compared with other techniques: OP accuracy rates were 95.5%, 93.1%, 91.5%, and 90.5%, via CTNav, FH, FA, and RA techniques, respectively. RA and CTNav were associated with the highest PS accuracy in the thoracic spine, compared with FH.

CONCLUSIONS

The OP data show that CTNav has the highest PS accuracy rates. Thoracic PSs were associated with lower accuracy rates; however, RA showed fewer breaches in the thoracic spine compared with FH and FA. Given the heterogeneity among studies, further standardized and comparative investigations are required to confirm our findings.

Inertial Measurement Unit-Assisted Implantation of Pedicle Screws in Combination With an Intraoperative 3-Dimensional/2-Dimensional Visualization of the Spine

BACKGROUND

Inertial measurement units (IMUs) are microelectromechanical systems used to track orientation and motion.

OBJECTIVE

To use instruments mounted with IMUs in combination with a 3- and 2-dimensional (3D/2D) rendering of the computed-tomography scan (CT) to guide implantation of pedicle screws.

METHODS

Pedicle screws were implanted from T1 to S1 in 2 human cadavers. A software application enabled the surgeon to select the starting points and trajectories on a 3D/2D image of the spine, then locate these starting points on the exposed spine and apply the IMU-mounted instruments to reproduce the trajectories. The position of the screws was evaluated on the postoperative CT scan.

RESULTS

A total of 72 pedicle screws were implanted. Thirty-seven (77%) of the thoracic screws were within the pedicle (Heary I), 7 (15%) showed a lateral breach of the pedicle, and 4 (8%) violated the anterior or lateral vertebral body (Heary III). In the lumbar spine and S1, 21 screws (88%) were within the pedicle (Gertzbein 0), 2 (8%) screws had a pedicle wall breach < 2 mm (Gertzbein 1), and 1 > 2 to < 4 mm (Gertzbein 2). In the second cadaver, the position was compared to the intraoperatively shown virtual position. The median offset was 3°(mean 3° ± 2°, variance 5, range 0°-9°) in the sagittal plane and 3° (mean 4° ± 3°, variance 9, range 0°-12°) in the axial plane.

CONCLUSION

IMU-assisted implantation of pedicle screws combined with an intraoperative 3D/2D visualization of the spine enabled the surgeon to precisely implant pedicle screws on the exposed spine.

ACCURACY OF PEDICLE SCREW INSERTION: A COMPARISON BETWEEN FLUOROSCOPIC GUIDANCE AND NAVIGATION TECHNIQUES

Objectives:

To compare the accuracy of insertion of pedicle screws into the thoracic spine using fluoroscopic guidance or computer-assisted navigation techniques.

Methods:

Eight cadaveric thoracic spines were divided into two groups: the fluoroscopy group, in which pedicle screws were inserted with the guidance of a C-arm device, and the navigation group, in which insertion of the screws was monitored using computer-assisted navigation equipment. All procedures were performed by the same spinal surgeon. The rate of pedicle breach was compared between the two groups.

Results:

There was one intra-canal perforation in each group. Both perforations were medial in direction, and the breaches were 2 to 4 mm deep. There were no statistically significant differences in breach rate between the two groups.

Conclusions:

The accuracy of insertion of pedicle screws in the thoracic spine using computer-assisted navigation is equivalent to that achieved using fluoroscopic guidance. Computer-assisted navigation improves the safety of the surgical team during the procedure due to the absence of exposure to radiation. Therefore, there is a need for future randomized controlled trials to be conducted in the clinical setting to evaluate other outcomes, including duration of surgery and blood loss during the procedure. Level of evidence IV.

Feasibility of Endoscopic Inspection of Pedicle Wall Integrity in a Live Surgery Model

Background

Perforations of the pedicle wall during cannulation can occur with experienced surgeons. Direct endoscopic visualization has not been used to inspect pedicles previously due to bone bleeding obscuring the camera visualization. The hypothesis of this study was that endoscopic visualization of pedicle wall integrity was technically feasible and would enable identification of clinically significant pedicle breaches.

Methods

A live porcine model was used. Eight lumbar pedicles were cannulated. Clinically significant breaches were created. An endoscope was introduced and was used to inspect the pedicles.

Results

All lumbar pedicles were endoscopically visible at a systolic pressure of 100 mm Hg. Clinically relevant anatomic structures and iatrogenic pathology, such as medial, lateral, and anterior breaches, were identified. There were no untoward events resulting from endoscopic inspection of the pedicle endosteal canal.

Conclusions

Endoscopic inspection of lumbar pedicles was safe and effective. The findings on endoscopic inspection corresponded with the ball-tip probe palpation techniques. Additional techniques, such as selection between 2 tracts, was possible with the endoscopic technique.

Pullout Strength of Pedicle Screws Following Redirection After Lateral or Medial Wall Breach

STUDY DESIGN

A cadaveric biomechanical study designed to test the pullout strength of pedicle screws.

OBJECTIVE

To evaluate the pullout strength of redirected pedicle screws with a larger diameter following lateral wall breach, redirected pedicle screws of the same diameter following medial wall breach, and redirected pedicle screws with a larger diameter following medial wall breach.

SUMMARY OF BACKGROUND DATA

Screw malposition is one of the main pitfalls of inserting pedicle screws. Intraoperatively a malpositioned screw is redirected and inserted along the correct axis.

METHODS

Forty-seven vertebrae (T9-L5) were harvested from eight fresh cadaveric spines. The 18 pedicle screws that breached the lateral wall were then removed and redirected using a pedicle screw of 1 mm larger in diameter. The 16 pedicle screws that had breached the medial wall were then removed and redirected using a pedicle screw of the same diameter. The other 13 pedicle screws that had breached the medial wall were then removed and redirected using a pedicle screw of 1 mm larger in diameter. The pullout strength was measured.

RESULTS

Following lateral wall breach, mean pullout strength for the larger redirected screws was 46.9% greater than that of the correctly aligned screws. Following medial wall breach, mean pullout strength for the redirected screws of the same diameter was 20.6% less than that of the correctly aligned screws. Mean pullout strength for the larger pedicle screws following medial wall breach was 27.3% more than that of the correctly aligned screws.

CONCLUSION

Redirected pedicle screws of larger diameter after a lateral or medial pedicle breach show recovery of pullout strength. However, the pullout strength of redirected pedicle screws of the same diameter after a medial pedicle breach is significantly less than that of correctly aligned screws.

LEVEL OF EVIDENCE

1.

Surgical Treatment of Recurrent Lumbar Disk Herniation: A Systematic Review and Meta-analysis

Consensus is lacking regarding optimal surgical treatment of recurrent lumbar disk herniation. A systematic search of multiple databases was conducted for studies evaluating outcomes after treatment for recurrent lumbar disk herniation. Treatment options included decompression surgeries and fusion surgeries. Although fusion surgeries eliminated re-recurrence of disk herniation, this coincided with higher incidences of complications and reoperation. Decompression surgeries and fusion surgeries both resulted in improvements in Japanese Orthopaedic Association, Oswestry Disability Index, and visual analog scale back and leg scores postoperatively (P<.05). The complication risk profiles of decompression surgeries and fusion surgeries must be balanced with the risk of disk herniation re-recurrence, as both procedures lead to improvements in functional outcomes. [Orthopedics. 2018; 41(4):e457-e469.].

Accuracy of percutaneous pedicle screws for thoracic and lumbar spine fractures compared with open technique

BACKGROUND

This study aimed to compare the accuracy of screw placement between open pedicle screw fixation and percutaneous pedicle screw fixation (MIS) for the treatment of thoracolumbar spine fractures (TSF).

METHODS

forty-nine patients with acute TSF who were treated with transpedicular screw fixation from January 2013 to December 2016 were retrospectively reviewed. The patients were divided into Open and MIS groups. Laminectomy was performed in either group if needed. The accuracy of the screw placement, the evolution of the Cobb sagittal angle postoperatively and at 12-month follow-up and the neurological status were recorded. AO type of fracture and TLICS score were also recorded.

RESULTS

Mean age was 42 years old. Mean TLICS score was 6.29 and 5.96 for open and MIS groups respectively. Twenty-five MIS and 24 open surgeries were performed, and 350 (175 in each group) screws were inserted (7.14 per patient). Twenty-four and 13 screws were considered "out" in the open and MIS groups respectively (Odds ratio 1.98. 0.97-4,03 P=0.056). The Cobb sagittal angle went from 13.3º to 4.5º and from 14.9º to 8.2º in the Open and MIS groups respectively (both P<0.0001). Loss of correction at 12-month follow-up was 3.2º and 4.2º for the open and MIS groups, respectively. No neurological worsening was observed.

CONCLUSIONS

For the treatment of acute thoracolumbar fractures, the MIS technique seems to achieve similar results to the open technique in relation to neurological improvement and deformity correction, while placing the screws more accurately.

A deep learning framework for segmentation and pose estimation of pedicle screw implants based on C-arm fluoroscopy

PURPOSE

Pedicle screw fixation is a challenging procedure with a concerning rates of reoperation. After insertion of the screws is completed, the most common intraoperative verification approach is to acquire anterior-posterior and lateral radiographic images, based on which the surgeons try to visually assess the correctness of insertion. Given the limited accuracy of the existing verification techniques, we identified the need for an accurate and automated pedicle screw assessment system that can verify the screw insertion intraoperatively. For doing so, this paper offers a framework for automatic segmentation and pose estimation of pedicle screws based on deep learning principles.

METHODS

Segmentation of pedicle screw X-ray projections was performed by a convolutional neural network. The network could isolate the input X-rays into three classes: screw head, screw shaft and background. Once all the screw shafts were segmented, knowledge about the spatial configuration of the acquired biplanar X-rays was used to identify the correspondence between the projections. Pose estimation was then performed to estimate the 6 degree-of-freedom pose of each screw. The performance of the proposed pose estimation method was tested on a porcine specimen.

RESULTS

The developed machine learning framework was capable of segmenting the screw shafts with 93% and 83% accuracy when tested on synthetic X-rays and on clinically realistic X-rays, respectively. The pose estimation accuracy of this method was shown to be [Formula: see text] and [Formula: see text] on clinically realistic X-rays.

CONCLUSIONS

The proposed system offers an accurate and fully automatic pedicle screw segmentation and pose assessment framework. Such a system can help to provide an intraoperative pedicle screw insertion assessment protocol with minimal interference with the existing surgical routines.

Transmuscular Ultrasonography of the Placement of Thoracolumbar Pedicle Screws: A Cadaveric Study

BACKGROUND

Transpedicular screw fixation has a biomechanical advantage of improving fusion rates. In posterior thoracolumbar immobilization, a large number of screws cause perforation to the pedicle or vertebral body. Radiography and computed tomography (CT) have been used to minimize this complication. The ability of ultrasound (US) to detect the pedicle breach during placement of the screw is unknown. The aim of this study was to evaluate the sensitivity of US for detecting breaches.

METHODS

A B-type transducer was used to scan 216 titanium pins inserted into cadaveric pedicles. Of the pins, 180 were intentionally misplaced: 90 pins breached the lateral wall of the pedicle, and 90 pins pierced the anterior wall of the vertebral body. US images were reviewed by 3 examiners blinded to both the procedure and the corresponding CT findings. The perforation length of pins was measured by 3 radiologists on CT images.

RESULTS

CT data were divided into 2 groups. In group 1 (perforation length 0-2 mm), sensitivity of US for detecting lateral wall and anterior wall perforation was 80.95% and 76.42%, respectively; in group 2 (perforation length 2-4 mm), sensitivity was 94.79% and 91.93%. Overall sensitivity of US to detect lateral wall and anterior wall perforation was 89.63% and 86.30%, respectively. The sensitivity of US for detecting perforation was greater in the lateral wall than in the anterior wall. Sensitivity of US was greater in group 2 than group 1 for both lateral and anterior perforation.

CONCLUSIONS

US can be applied to detect perforation of ≤4 mm. Use of US may improve patient safety.

An intraoperative fluoroscopic method to accurately measure the post-implantation position of pedicle screws

PURPOSE

Pedicle screw malplacement, leading to neurological symptoms, vascular injury, and premature implant loosening, is not uncommon and difficult to reliably detect intraoperatively with current techniques. We propose a new intraoperative post-placement pedicle screw position assessment system that can therefore allow surgeons to correct breaches during the procedure. Our objectives were to assess the accuracy and robustness of this proposed screw location system and to compare its performance to that of 2D planar radiography.

METHODS

The proposed system uses two intraoperative X-ray shots acquired with a standard fluoroscopic C-arm and processed using 2D/3D registration methods to provide a 3D visualization of the vertebra and screw superimposed on one another. Point digitization and CT imaging of the residual screw tunnel were used to assess accuracy in five synthetic lumbar vertebral models (10 screws in total). Additionally, the accuracy was evaluated with and without correcting for image distortion and for various screw lengths, screw materials, breach directions, and vertebral levels.

RESULTS

The proposed method is capable of localizing the implanted screws with less than 2 mm of translational error (RMSE: 0.7 and 0.8 mm for the screw head and tip, respectively) and less than [Formula: see text] angular error (RMSE: [Formula: see text]), with minimal change to the errors if image distortion is not corrected. Breaches and their anatomical locations were all correctly visualized and identified for a variety of screw lengths, screw materials, breach locations, and vertebral levels, demonstrating the robustness of this approach. In contrast, one breach, one non-breach, and the anatomical location of three screws were misclassified with 2D X-ray.

CONCLUSION

We have demonstrated an accurate and low-radiation technique for localizing pedicle screws post-implantation that requires only two X-rays. This intraoperative feedback of screw location and direction may allow the surgeon to correct malplaced screws intraoperatively, thereby reducing postoperative complications and reoperation rates.

Biomechanical Analysis of Lateral Lumbar Interbody Fusion Constructs with Various Fixation Options: Based on a Validated Finite Element Model

BACKGROUND

Lateral lumbar interbody fusion using cage supplemented with fixation has been used widely in the treatment of lumbar disease. A combined fixation (CF) of lateral plate and spinous process plate may provide multiplanar stability similar to that of bilateral pedicle screws (BPS) and may reduce morbidity. The biomechanical influence of the CF on cage subsidence and facet joint stress has not been well described. The aim of this study was to compare biomechanics of various fixation options and to verify biomechanical effects of the CF.

METHODS

The surgical finite element models with various fixation options were constructed based on computed tomography images. The lateral plate and posterior spinous process plate were applied (CF). The 6 motion modes were simulated. Range of motion (ROM), cage stress, endplate stress, and facet joint stress were compared.

RESULTS

For the CF model, ROM, cage stress, and endplate stress were the minimum in almost all motion modes. Compared with BPS, the CF reduced ROM, cage stress, and endplate stress in all motion modes. The ROM was reduced by more than 10% in all motion modes except for flexion; cage stress and endplate stress were reduced more than 10% in all motion modes except for rotation-left. After interbody fusion, facet joint stress was reduced substantially compared with the intact conditions in all motion modes except for flexion.

CONCLUSIONS

The combined plate fixation may offer an alternative to BPS fixation in lateral lumbar interbody fusion.

Improved accuracy of screw implantation could decrease the incidence of post-operative hydrothorax? O-arm navigation vs. free-hand in thoracic spinal deformity correction surgery

PURPOSE

The purpose of this study was to analyze the occurrence of PE after intra-operative O-arm navigation-assisted surgery and determine whether the post-operative PE incidence could be decreased by using O-arm navigation as compared to conventional free-hand technique.

METHODS

A cohort of 27 patients with spinal deformity who were operated upon with an O-arm navigated system (group A) between 2013 and 2016 were enrolled in the study. A total of 27 curve-matched patients treated by conventional free-hand technique were included as the control group (group B). Whole spine posterior-anterior and lateral radiographs, and CT scans were taken pre and post-operation. Radiologic parameters and volume of PE were measured and compared between the two groups.

RESULTS

There were no significant differences in age, Cobb angle, and sagittal contour between the two groups pre-operatively. The mean total volume of post-operative PE was significantly larger in the free-hand group (p < 0.001). In the O-arm group, 59 malpositioned screws were identified in 22 patients. In the free-hand group, 88 malpositioned screws were found among 26 patients. The screw perforation rate was higher in the free-hand group than in the O-arm group (p = 0.007). In the O-arm group, the mean volume of PE was significantly larger among patients with malpositioned screws than those without malpositioned screws (p < 0.001), as well as in the free-hand group.

CONCLUSION

The volume of PE after correction surgery can be significantly decreased by application of O-arm navigation system as compared to conventional free-hand technique. We ascribed the improvement to the accuracy of screw implantation navigated by O-arm.

MIS Single-position Lateral and Oblique Lateral Lumbar Interbody Fusion and Bilateral Pedicle Screw Fixation: Feasibility and Perioperative Results

STUDY DESIGN

Retrospective review of prospectively collected data of the first 72 consecutive patients treated with single-position one- or two-level lateral (LLIF) or oblique lateral interbody fusion (OLLIF) with bilateral percutaneous pedicle screw and rod fixation by a single spine surgeon.

OBJECTIVE

To evaluate the clinical feasibility, accuracy, and efficiency of a single-position technique for LLIF and OLLIF with bilateral pedicle screw and rod fixation.

SUMMARY OF BACKGROUND DATA

Minimally-invasive lateral interbody approaches are performed in the lateral decubitus position. Subsequent repositioning prone for bilateral pedicle screw and rod fixation requires significant time and resources and does not facilitate increased lumbar lordosis.

METHODS

The first 72 consecutive patients (300 screws) treated with single-position LLIF or OLLIF and bilateral pedicle screws by a single surgeon between December 2013 and August 2016 were included in the study. Screw accuracy and fusion were graded using computed tomography and several timing parameters were recorded including retractor, fluoroscopy, and screw placement time. Complications including reoperation, infection, and postoperative radicular pain and weakness were recorded.

RESULTS

Average screw placement time was 5.9 min/screw (standard deviation, SD: 1.5 min; range: 3-9.5 min). Average total operative time (interbody cage and pedicle screw placement) was 87.9 minutes (SD: 25.1 min; range: 49-195 min). Average fluoroscopy time was 15.0 s/screw (SD: 4.7 s; range: 6-25 s). The pedicle screw breach rate was 5.1% with 10/13 breaches measured as < 2 mm in magnitude. Fusion rate at 6-months postoperative was 87.5%. Two (2.8%) patients underwent reoperation for malpositioned pedicle screws with subsequent resolution of symptoms.

CONCLUSION

The single-position, all-lateral technique was found to be feasible with accuracy, fluoroscopy usage, and complication rates comparable with the published literature. This technique eliminates the time and staffing associated with intraoperative repositioning and may lead to significant improvements in operative efficiency and cost savings.

LEVEL OF EVIDENCE

4.

Anatomical differences in the bony structure of L5 and L4: A possible classification according to the lateral tilt of the pedicles

The aim of this study is to underline the necessity of a better knowledge of pedicles anatomy in order to improve surgical treatment of spine disorders such us low back pain, spinal fractures and scholiosis. A classification of pedicles lateral tilt which could help surgeons before the application of screws during transpedicular fixation is reported. Anatomical differences in the orientiation of the pedicles of L5 and L4 have been found. For each patient that met the inclusion criteria underwent: Radiography of the lumbo-sacral region, CT examination, MRI acquisition. Patients were divided into three categories thanks to 3D direct volume rendering of CT scan. Subjects belonged to W-Type, V-Type and U-type depending on their morphometric features. The subdivision was further implemented with measurements of the distance between pedicles and adjacent nervous structures. Concerning L5, W-Type (WT) exhibited a lateral tilt of L5 larger than 36°, V-Type exhibited a lateral tilt of L5 from 30° to 36°, U-type exhibited a lateral tilt of L5 smaller than 30°. Concerning L4, WT exhibited a lateral tilt of 28.4°, VT exhibited a lateral tilt of of 25.1, UT exhibited a lateral tilt of 22.2°; we assume that the degree of lateralization of L4 depends on the one of L5. The way the screw is applied during surgical treatment is clinically relevant, thus our classification may be very useful in order to decrease surgical risk and improve conditions of patients after surgical treatment.

Accuracy of 837 pedicle screw positions in degenerative lumbar spine with conventional open surgery evaluated by computed tomography

BACKGROUND

The spatial and directional accuracy of the positioning of pedicle screws in the lumbosacral spine with conventional open surgery assessed by computed tomography (CT) has been published in several studies, systematic reviews and meta-analyses with a short-term follow-up. Inaccurate pedicle screw insertion may cause neurologic symptoms and weakens the construct.

METHODS

The data of 147 patients operated on with transpedicular screw fixation based on anatomical landmarks, supported by fluoroscopy, by a senior neurosurgeon in our clinic between 2000 and 2010 were analyzed retrospectively. The accuracy of the pedicle screw position was assessed by using postoperative CT images and graded in 2-mm increments up to 6 mm by two independent surgeons and partly by an independent radiologist.

RESULTS

A total of 837 lumbosacral pedicle screws were inserted in 147 randomly selected patients by a senior neurosurgeon. A mean accuracy of 85.7% of the screws being inside the pedicles was identified by the surgeon observers, with 3.3% being perforated 4 mm or more outside the pedicles. Postoperative neurologic symptoms were observed on the side corresponding to the breach in an average of 25.9% of patients with pedicle perforations, and 89.2% of the misplaced screws were either medially or inferiorly inserted.

CONCLUSIONS

Screw application reached a mean accuracy of 85.7% based on anatomical landmarks supported by fluoroscopy, warranting computer-assisted navigation for increased accuracy. Our results of 24 patients (16.3%) with the breached screws indicate that the direction of the breach may be more important than the absolute deviation in causing new neurologic symptoms.