Pedicle Screw Placement Research Articles

The "V" Sign: A Reliable Anatomic and Radiographic Landmark for Posterior Percutaneous S1 Screw Placement.

Sacral (S1) pedicle screw misplacement in posterior percutaneous fixation (PPF) can be related to anatomical variability and a lack of reliable radiographic landmarks. This study highlights a reproducible anatomical landmark (the "V" sign) for the safe localization of the S1 pedicle entry point under fluoroscopy. Human cadavers (n = 14) were dissected for the anatomical description of the "V" landmark and its relationship with the entry point of the S1 pedicle screw. The "V" landmark was defined medially by the lateral border of the superior articulating process of S1 and laterally by the posterior projection of the sacral ala. The mean distance was measured between the bottom point of the "V" landmark and the anatomical entry point to the S1 pedicle (V-S1 entry point distance). A similar measurement was conducted on computed tomography (CT) scans of 135 patients who underwent PPF using the "V" sign as a landmark for S1 pedicle screw placement (270 screws). These were retrospectively evaluated for appropriateness of S1 screw entry points and for proper S1 screw alignment and breaches. In the 14 cadavers, irrespective of the laterality and sex, the V-S1 entry point distance averaged 11.7 mm. On the medial-lateral axis, all entry points converged within 2 mm of a vertical line intersecting the base of the "V." Additionally, the CT scan analysis (135 patients, 270 screws) revealed an optimal entry point for 100% of the screws and a 3.3% (n = 9 screws) breach rate. Six of the 9 identified breaches were minor, and only 1 (0.4% of the 270 screws) warranted revision. The "V" sign serves as a reliable anatomical and radiographic landmark for identifying the S1 pedicle entry point under fluoroscopic guidance. This landmark can help surgeons overcome the radiographic ambiguity of the sacral anatomy and ultimately reduces the rate of S1 pedicle screw misplacement. Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Accuracy of computer-assisted pedicle screw placement for adolescent idiopathic scoliosis: a comparison between robotics and navigation

To compare the accuracy of pedicle screw placement in adolescent idiopathic scoliosis (AIS) between robotics and navigation and clarify the factors that cause screw deviation when robotics is used. Fifty consecutive patients who underwent posterior spinal fusions with computer-assisted pedicle screw placement including robotics and navigation for AIS were included. A total of 741 pedicle screws (250: Robot group, 491: Navi group) were evaluated on postoperative CT images. A rate of penetration of ≥ 2mm was calculated as the deviation rate. After propensity score matching, we examined vertebral levels, the distance from the reference frame (RF), and the pedicle channel grade as factors for deviation. The deviation rate was significantly lower in the Robot group than in the Navi group (Robot group: 1.6%, Navi group: 7.5%). After propensity score matching, 22 cases were extracted. At T5-T8, the deviation rate of the Robot group was significantly lower than that of the Navi group. In the Robot group, the T2-T4 deviation rate was significantly higher than at the other vertebral levels. The distance from the RF didn't affect the deviation rate. The deviation rate of pedicle channel Grade 4 (inner diameter of less than 1mm) was significantly higher than for the other grades. The deviation rate of robotics was 1.6%, lower than that of navigation. The narrow pedicles with an inner diameter of less than 1mm (deviation rate: 22.2%) and the upper thoracic level (deviation rate: 14.3%) were factors related to screw deviation even when using robotics.

The association between paraspinal muscle parameters and vertebral pedicle microstructure in patients undergoing lumbar fusion surgery.

Lumbar fusion surgery has become a standard procedure in spine surgery and commonly includes the posterior placement of pedicle screws. Bone quality is a crucial factor that affects pedicle screw purchase. However, the relationship between paraspinal muscles and the bone quality of the pedicle is unknown. The aim of the study was to determine the relationship between paraspinal muscles and the ex vivo bony microstructure of the lumbar pedicle. Prospectively, collected data of patients undergoing posterior lumbar fusion for degenerative spinal conditions was analyzed. Pre-operative lumbar magnetic resonance imaging (MRI) scans were evaluated for a quantitative assessment of the cross-sectional area (CSA), functional cross-sectional area (fCSA), and the proportion of intramuscular fat (FI) for the psoas muscle and the posterior paraspinal muscles (PPM) at L4. Intra-operative bone biopsies of the lumbar pedicle were obtained and analyzed with microcomputed tomography (µCT) scans. The following cortical (Cort) and trabecular (Trab) bone parameters were assessed: bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), connectivity density (CD), bone-specific surface (BS/BV), apparent density (AD), and tissue mineral density (TMD). A total of 26 patients with a mean age of 59.1years and a mean BMI of 29.8kg/m2 were analyzed. fCSAPPM showed significant positive correlations with BV/TVTrab (ρ = 0.610; p < 0.001), CDTrab (ρ = 0.679; p < 0.001), Tb.NTrab (ρ = 0.522; p = 0.006), Tb.ThTrab (ρ = 0.415; p = 0.035), and ADTrab (ρ = 0.514; p = 0.007). Cortical bone parameters also demonstrated a significant positive correlation with fCSAPPM (BV/TVCort: ρ = 0.584; p = 0.002; ADCort: ρ = 0.519; p = 0.007). FIPsoas was negatively correlated with TMDCort (ρ = - 0.622; p < 0.001). This study highlights the close interactions between the bone microstructure of the lumbar pedicle and the paraspinal muscle morphology. These findings give us further insights into the interaction between the lumbar pedicle microstructure and paraspinal muscles.

Reduction in Radiation Exposure in Minimally Invasive Pedicle Screw Placement Using a Tubular Retractor: A Pilot Study

Percutaneous pedicle screw (PPS) placement is a minimally invasive spinal procedure that has been rapidly adopted over the last decade. However, PPS placement has elicited fear of increased radiation exposure from some surgeons, medical staff, and patients. This is because PPS placement is performed using a K-wire, and the operator must perform K-wire insertion into the pedicle under fluoroscopy. In order to prevent erroneous insertion, there are many occasions when direct insertion is required during radiation exposure, and the amount of radiation exposure to hands and fingers in particular increases. Although these problems are being addressed by navigation systems, these systems are still expensive and not widely available. Attempts have been made to address this situation using instrumentation commonly used in spinal surgery. First, it was considered to visualize anatomical bone markers using a tubular retractor and a microscope. In addition, the use of a self-drilling pin was adopted to locate the pedicle in a narrower field of view. Based on these considerations, a minimally invasive and highly accurate pedicle screw placement technique was developed while avoiding direct radiation exposure. This study evaluated radiation exposure and accuracy of pedicle screw placement using this new procedure in one-level, minimally invasive, transforaminal lumbar interbody fusion (MIS-TLIF). Data were collected retrospectively to review pedicle screw placement in single-level MIS TLIFs using a tubular retractor under a microscope. The total fluoroscopy time, radiation dose, and screw placement accuracy were reviewed. Extension of operating time was also evaluated. Twenty-four patients underwent single-level MIS TLIFs, with placement of 96 pedicle screws. There were 15 females and 9 males, with an average age of 64.8 years and a mean body mass index of 25.5 kg/m2. The mean operating time was 201.8 min. The mean fluoroscopic time was 26.8 s. The mean radiation dose of the area dose product was 0.0706 mGy∗m2. The mean radiation dose of air kerma was 6.0 mGy. The mean radiation dose of the entrance skin dose was 11.31 mGy. Postoperative computed tomography scans demonstrated 93 pedicle screws confined to the pedicle (97%) and three pedicle screw breaches (3.2%; two lateral, one medial). A patient with screw deviation of the medial pedicle wall developed right-foot numbness necessitating reoperation. There were no complications after reoperation. The average added time with this combined procedure was 39 min (range 16-69 min) per patient. This novel pedicle screw insertion technique compares favorably with other reports in terms of radiation exposure reduction and accuracy and is also useful from the viewpoint of avoiding direct radiation exposure to hands and fingers. It is economical because it uses existing spinal surgical instrumentation.

What Is Next in Computer-Assisted Spine Surgery? Advances in Image-Guided Robotics and Extended Reality

Background: This article provides a scoping review on the current status of Image-Guided Navigation with various forms of digital technologies, including Extended Reality, Augmented Reality Head-Mounted Displays (AR–HMDs) and Robot-Assisted Surgery (RAS) for Pedicle Screw Placement in orthopedics and spine surgery. Methods: A scoping literature review was performed in the PubMed, Scopus, Embase, Web of Science, Google Scholar and IEEE Xplore databases to collect clinical and user satisfaction data on AR–HMDs and compare those with RAS outcomes. In vivo patient, cadaver and phantom trial accuracy data reports were identified and grouped through the analysis. Over the past two years, 14 publications were retrieved and analyzed. Pedicle screw placement accuracy was described with Linear Tip Error (LTE), Angular Trajectory Error (ATE) and Gertzbein–Robbins Scale (GRS) outcomes. Results: The Pedicle Screw Placement accuracy was seen to increase in the in vivo, cadaver and phantom model groups using AR-HMD compared to the Free-Hand insertion technique. User experience and satisfaction data were limited; however, a clear advantage for the operative results was described when it was added. RAS screwing showed similar accuracy outcomes. The need for benchmarking and quantified situation awareness for AR–HMDs is recognizable. The authors present a method for standardized scoring and visualization of surgical navigation technologies, based on measurements of the surgeon (as the end-users) user satisfaction, clinical accuracy and operation time. Conclusions: computer-technology driven support for spine surgery is well-established and efficient for certain procedures. As a more affordable option next to RAS, AR–HMD navigation has reached technological readiness for surgical use. Ergonomics and usability improvements are needed to match the potential of RAS/XR in human surgeries.

Feasibility of outpatient robot assisted minimally invasive transforaminal lumbar interbody fusion

IntroductionLumbar interbody fusion is a common spine procedure. 199,140 elective lumbar fusions were performed in the United States in 2015. Robot assisted (RA) pedicle screw placement has advanced minimally invasive spine surgery (MIS) making short stay transforaminal lumbar interbody fusions (TLIF) with same day or next day discharge a possibility for select patients. MethodsThis study is a retrospective case series of a single surgeon's experience with RA MIS TLIF using the Globus ExcelsiusGPS system. Patients undergoing RA MIS TLIF at an outpatient surgery center between August 2020 and February 2021 were included in the study. ResultsTwenty-three patients met inclusion criteria. Ninety-six RA pedicle screws and 25 interbody cages were placed. 96/96 (100%) pedicle screws and 25/25 (100%) interbodies were found to be in satisfactory position using intraoperative x-ray. None of the instrumentation required re-placement or revision intraoperatively. 20/23 (87%) patients were able to discharge within 24 hours of the procedure. 2/23 (8.7%) patients discharged on the day of surgery. One patient of 23 (4.3%) required discharge to an inpatient rehabilitation facility post operatively. 0/23 (0%) patients required readmission for pain control. ConclusionsOur study demonstrates the safety and feasibility of outpatient RA MIS TLIF for select patients. Future directions include a larger study to elucidate characteristics of the best candidates for outpatient RA MIS TLIF.

Comparison of 3D-printed Navigation Template-assisted Pedicle Screws versus Freehand Screws for Scoliosis in Children and Adolescents: A Systematic Review and Meta-analysis.

There is a lack of attention to screw placement techniques for surgical treatment of scoliosis in children and adolescents. This meta-analysis aims to compare the accuracy and safety of pedicle screw placement between the 3D-printed navigation template technique and the freehand technique during corrective surgery for scoliosis in children and adolescents. A comprehensive search was conducted for relevant articles up to December 2021 in databases including PubMed, Embase, MEDLINE, Cochrane, and Web of Science. The systematic meta-analysis compared the efficacy of pedicle screw placement between the two techniques, including accuracy of pedicle screw placement, complication rate, operation time, blood loss, mean placement time per screw, and mean times for fluoroscopy. The seven articles analyzed in this study involved 229 patients altogether. A total of 2,805 pedicle screws were placed by the two methods. Our results revealed that the 3D-printed guide template technique was more accurate than the freehand technique in pedicle screw placement (odds ratio [OR] =2.96; 95% confidence interval [CI]: 2.24-3.91; p < 0.000) with a lower complication rate (OR = 0.21; 95% CI: 0.06-0.78; p = 0.02). The operation time (mean difference [MD] = -34.37; 95% CI: -67.47 to -1.28; p = 0.04) and mean placement time per screw (MD = -3.11; 95% CI: -6.13 to -0.09; p = 0.04) and mean times for fluoroscopy (MD = -6.60; 95% CI: -8.66 to -4.55; p < 0.000) significantly decreased among patients in the 3D-printed navigation template group compared with those in the freehand technique group. In addition, the two techniques had no significant statistical difference in blood loss. Compared with the traditional freehand technique, the 3D-printed guide template is a promising technique with higher accuracy and safety in screw placement for surgical treatment of scoliosis in children and adolescents, and is worth popularizing and validating through more prospective clinical studies.

Comparison of the O-arm and C-arm guided pedicle screws placement

Comparison of the O-arm and C-arm guided pedicle screws placement

Task-specific robot base pose optimization for robot-assisted surgeries.

Preoperative planning and intra-operative system setup are crucial steps to successfully integrate robotically assisted surgical systems (RASS) into the operating room. Efficiency in terms of setup planning directly affects the overall procedural costs and increases acceptance of RASS by surgeons and clinical personnel. Due to the kinematic limitations of RASS, selecting an optimal robot base location and surgery access point for the patient is essential to avoid potentially critical complications due to reachability issues. To this end, this work proposes a novel versatile method for RASS setup and planning based on robot capability maps (CMAPs). CMAPs are a common tool to perform workspace analysis in robotics, as they are in general applicable to any robot kinematics. However, CMAPs have not been completely exploited so far for RASS setup and planning. By adapting global CMAPs to surgical procedure-specific tasks and constraints, a novel RASS capability map (RASSCMAP) is generated. Furthermore, RASSCMAPs can be derived to also comply with kinematic access constraints such as access points in laparoscopy. RASSCMAPs are versatile and applicable to any kind of surgical procedure; they can be used on the one hand for aiding in intra-operative experience-based system setup by visualizing online the robot's capability to perform a task. On the other hand, they can be used to find the optimal setup by applying a multi-objective optimization based on a genetic algorithm preoperatively, which is then transfered to the operating room during system setup. To illustrate these applications, the method is evaluated in two different use cases, namely, pedicle screw placement in vertebral fixation procedures and general laparoscopy. The proposed RASSCMAPs help in increasing the overall clinical value of RASS by reducing system setup time and guaranteeing proper robot reachability to successfully perform the intended surgeries.

Robot-assisted pedicle screw placement

Pedicle screw-based posterior instrumentation of the spine. Instability of the spine due to trauma, infection, degenerative spinal disease or tumor. None. Robot-assisted navigated pedicle screw placement. Early functional mobilization starting on the first postoperative day. Astudy by Lee etal. analyzed the clinical application of the system MazorX Stealth Edition (Medtronic Navigation, Louisville, CO, USA; Medtronic Spine, Memphis, TN, USA) in 186cases with atotal of 1445 pedicle screws [1]. Correct screw positioning was achieved in 1432 pedicle screws (99.1%); six pedicle screws (0.4%) were revised intraoperatively. The mean duration of pedicle screw placement was 6.1 ± 2.3 min. Pojskić etal. published acase series regarding the application of the system Cirq (Brainlab, Munich, Germany) in 13cases with atotal number of 70pedicle screws implanted [2]. Intraoperative imaging showed screw positioning according to the Gertzbein Robbins classification (GR) categoryA in 65screws (92.9%) and GRB in one screw (1.4%). Screw positioning GRD with intraoperative revision was reported in two screws (2.9%). Mean duration of pedicle screw placement was 08:27 ± 06:54 min.

Comparison of the Accuracy of Pedicle Screw Placement Using a Fluoroscopy-Assisted Free-Hand Technique with Robotic-Assisted Navigation Using an O-Arm or 3D C-Arm in Scoliosis Surgery.

Retrospective. To report and compare the application of robotic-assisted navigation with an O-arm or three-dimensional (3D) C-arm-assisted pedicle screw insertion in scoliosis surgery, and compare with free-hand technique. One hundred and forty-four scoliosis patients were included in this study. Ninety-two patients underwent robotic-assisted pedicle screw insertion (Group A), and 52 patients underwent freehand fluoroscopy-guided pedicle screw insertion (Group B). Group A was further divided into Subgroup AI (n = 48; robotic-assisted navigation with an O-arm) and Subgroup AII (n = 44; robotic-assisted navigation with a 3D C-arm). The evaluated clinical outcomes were operation time, blood loss, radiation exposure, postoperative hospital stay, and postoperative complications. The clinical outcomes, coronal and sagittal scoliosis parameters and the accuracy of the pedicle screw placement were assessed. There were no significant differences in blood loss and postoperative hospital stay between Groups A and B (P = .406, P = .138, respectively). Radiation exposure for patients in Group A (Subgroups AI or AII) was higher than that in Group B (P < .005), and Subgroup AI had higher patient radiation exposure compared with Subgroup AII (P < .005). The operation time in Subgroup AII was significantly longer than that in Subgroup AI and Group B (P = .016, P = .032, respectively). The proportion of clinically acceptable screws was higher in Group A (Subgroups AI or AII) compared with Group B (P < .005). Robotic-assisted navigation with an O-arm or 3D C-arm effectively increased the accuracy and safety in scoliosis surgery. Compared with robotic-assisted navigation with a 3D C-arm, robotic-assisted navigation with an O-arm was more efficient intraoperatively.

Robotic-assisted spine surgery allows for increased pedicle screw sizes while still improving safety as indicated by elevated triggered electromyographic thresholds

The present study used triggered electromyographic (EMG) testing as a tool to determine the safety of pedicle screw placement. In this Institutional Review Board exempt review, data from 151 consecutive patients (100 robotic; 51 non-robotic) who had undergone instrumented spinal fusion surgery of the thoracic, lumbar, or sacral regions were analyzed. The sizes of implanted pedicle screws and EMG threshold data were compared between screws that were placed immediately before and after adoption of the robotic technique. The robotic group had significantly larger screws inserted that were wider (7 ± 0.7 vs 6.5 ± 0.3 mm; p < 0.001) and longer (47.8 ± 6.4 vs 45.7 ± 4.3 mm; p < 0.001). The robotic group also had significantly higher stimulation thresholds (34.0 ± 11.9 vs 30.2 ± 9.8 mA; p = 0.002) of the inserted screws. The robotic group stayed in the hospital postoperatively for fewer days (2.3 ± 1.2 vs 2.9 ± 2 days; p = 0.04), but had longer surgery times (174 ± 37.8 vs 146 ± 41.5 min; p < 0.001). This study demonstrated that the use of navigated, robot-assisted surgery allowed for placement of larger pedicle screws without compromising safety, as determined by pedicle screw stimulation thresholds. Future studies should investigate whether these effects become even stronger in a later cohort after surgeons have more experience with the robotic technique. It should also be evaluated whether the larger screw sizes allowed by the robotic technology actually translate into improved long-term clinical outcomes.

Treatment of thoracolumbar fractures: comparison of the clinical and radiological outcomes of percutaneous versus open surgery.

Retrospective study. Spinal fractures are common trauma that can be treated by a range of techniques, from functional to surgical. Spine surgery has been around for many years. The first procedures were done open but have been plagued by numerous complications-sometimes severe-and substantial intraoperative blood loss. Percutaneous surgery was developed to help reduce the complications while providing similar clinical and radiological outcomes to open surgery. We conducted a study to compare open and percutaneous surgery and to evaluate other complications as well as short- and medium-term clinical and radiological results. Retrospective, single-center study comparing two cohorts of patients suffering from an isolated vertebral fracture who were operated using either an open or percutaneous technique. Included were patients who had an isolated vertebral fracture between T10 and L3 and were operated between 01/01/2016 and 31/12/2018 at the Reims university hospital. These patients were reviewed in person after a minimum of 18months postoperative for clinical and radiological assessments. The Mercuriali and Brecher formula was used to calculate intraoperative blood loss based on pre- and postoperative hematocrit; the total blood volume was determined with the Nadler formula. The study cohort consisted of 79 patients operated by percutaneous surgery and 55 patients operated by open surgery. The blood loss in the percutaneous surgery group was 176mL versus 220mL in the open surgery group (p = 0.02). The length of hospital stay was shorter after percutaneous surgery (mean of 3.6days) than after open surgery (mean of 5.5days) (p < 0.001). Also, the pedicle screw placement was optimal in 88% of percutaneous procedures versus 67% of open procedures (p < 0.001). Percutaneous surgery for thoracolumbar fractures causes less blood loss than conventional open surgery. The clinical and radiological results are on par with conventional open surgery. The mean length of hospital stay is shorter and the accuracy of pedicular screw placement is higher with percutaneous surgery. Thus, we can conclude that percutaneous surgery is the preferred treatment for thoracolumbar fractures when no neurological deficit is present. IV.

Spinal navigation with preoperative computed tomography

Safe placement of posterior cervical-sacral pedicle screws, S2-Ala-iliac screws, iliac screws, transarticular screws C1/2, translaminar screws C2 or cervical lateral mass screws under the guidance of spinal navigation. All posterior spinal instrumentations with screws: instabilities and deformities of rheumatic, traumatic, neoplastic, infectious, iatrogenic or congenital origin; multilevel cervical spinal stenosis with degenerative instability or kyphosis of the affected spinal segment. There are no absolute contraindications for spinal navigation. Cervical spine: Prone position on agel mattress, rigid head fixation, e.g., with Mayfield tongs; if appropriate, closed reduction under lateral image intensification; thoracic + lumbar spine: prone position on acushioned frame; midline posterior surgical approach at the level of the segments to be instrumented; if necessary, open reduction; insertion of the cervical/upper thoracic screws under the guidance of spinal navigation; if necessary, posterior decompression; instrumentation longitudinal rods; if fusion is to be obtained, decortication of the posterior bone elements with ahigh-speed burr and onlay of cancellous bone or bone substitutes. In stable instrumentations, no postoperative immobilization with orthosis is necessary, removal of drains (if used) 2-3days postoperatively (postop), removal of the sutures 14days postop, clinical and x‑ray controls 3and 12months postop or in case of clinical or neurological deterioration. Numerous studies showed that the use of spinal navigation significantly reduces implant malplacement rates, complications, and revision surgery. Furthermore, intraoperative radiation exposure to the operation team can be reduced by up to 90%.

Perpendicular probing and screwing technique: A simple method for accurate pedicle screw placement based on the human internal reference frame for angle estimation.

The pedicle screw (PS) is widely used for spinal fixation surgery. However, PS malpositioning can cause critical complications; thus, the accuracy of ascertaining PS trajectory is paramount. This study aimed to demonstrate the accuracy and safety of a simple and cost-effective PS placement technique using a human internal reference frame for angle estimation. Ex vivo lumbar porcine spine samples were fixed to a wooden board with rostrocaudal and mediolateral rotational angles adjusted by two angle vises. PS entry points (EPs) were identified using clear anatomical vertebral landmarks. PS placement was performed on one side using the perpendicular probing and screwing technique (PPST), wherein the attitude angle of the sample was adjusted such that the longitudinal axis of the target pedicle was perpendicular to the ground. The pedicle probe and PS driver were manually maintained perpendicular to the ground during probing and PS placement. PS placement on the contralateral side was performed freehand as a control. Offsets between the preoperatively planned and implanted PS rotational angles measured using computed tomography for PPST and freehand method were analyzed. Pedicle wall penetration was also evaluated. The mean ± standard error of the medial rotational offsets was 5.83° ± 0.57° in the freehand group versus 2.89° ± 0.31° in the PPST group (p <0.001), and the rostrocaudal rotational offsets were 4.81° ± 0.65° in the freehand group versus 2.92° ± 0.45° in the PPST group (p = 0.01). The mean pedicle wall penetration distance was significantly reduced by PPST (0.28 ± 0.12 mm vs 0.80 ± 0.17 mm in the freehand group, p = 0.0071). Thus, PPST improved PS positioning accuracy, resulting in reduced pedicle wall penetration and increased PS placement safety. This simple technique is also potentially cost-effective for institutions without computer-assisted surgical systems.

The Learning Curve of Robotic-Assisted Pedicle Screw Placements Using the Cumulative Sum Analysis: A Study of the First 50 Cases at a Single Center.

The purpose of this study was to clarify how many cases surgeons need to experience to pass the learning phase of robotic-assisted spine surgery using the cumulative sum (CUSUM) analysis. A retrospective review was conducted on the initial 50 consecutive patients who underwent robotic-assisted pedicle screw placements with open procedures using a spine robotic system (Mazor X Stealth Edition) at a single center from April 2021 to January 2022. There were 19 male and 31 female patients with a mean age of 58.7 (range, 13-86) years. To split the surgeries into the early and late phases using the CUSUM analysis of screw insertion time, we compared the screw insertion time, the robot setting time, the registration time, and the operation time in the early and late phases. The screw insertion time, the robot setting time, and the registration time declined as the number of surgical cases increased. The operation time did not decline as the number of surgical cases increased. The learning curve for screw insertion time can be separated into two stages based on the CUSUM analysis. The first 23 cases were in the early phase, and the later 27 cases were in the late phase. The mean screw insertion time was reduced from 3.2 min in the first 23 cases to 2.7 min in the subsequent 27 cases. The robot setting time and registration time in the late phase were also significantly shorter than those in the early phase. The screw insertion time, robot setting time, and registration time decreased with experience. After 23 cases, surgeons passed the learning phase of robotic-assisted spine surgery and became more proficient.

A superior articular process morphology of 5th lumbar vertebra prone to screws placement failure: an anatomical study of 299 patients

PurposesThis study aimed to investigate whether the morphology of the superior articular processes of L5 vertebra affected the accuracy of pedicle screw placement by reviewing 299 patients who had undergone L5 pedicle screw fixation over the past 12 months and measuring relevant parameters.MethodsWe retrospectively analyzed patients who underwent L5 vertebra fixation at our spine surgery department from October 20, 2020 to October 20, 2021. Patients with spondylolisthesis, spondylolysis, and scoliosis were excluded. Parameters associated with the superior articular process were analyzed, including Mammillary process-Spinal canal Distance (MCD), Inter-Facet Distance (IFD), Inter-Pedicle Distance (IPD), Zygapophysial Joints Angle (ZJA), Superior Articular Width, and Lateral Recess Transverse Diameter. The L5 vertebral body was reconstructed by Mimics 21.0, and the simulated L5 screws were inserted at multiple entry points to measure the Maximum Safe Transverse Angle (STAmax).ResultsA total of 299 patients who underwent L5 vertebra fixation with 556 pedicle screws were analyzed. An MCD < 6 mm was associated with a significant increase in screw placement failure rate and decrease in ZJA. The MCD was positively correlated with IFD. No significant change in IPD was observed. Mimics software analysis showed that the STAmax decreased with a decrease of MCD. When WBV < 6 mm, 93% of the trans-mammillary vertical line was located within 50% of the pedicle.ConclusionsThe superior articular process tended to narrow the spinal canal and exhibit a steep and a “cloverleaf” morphology when the MCD was < 6 mm. This morphology increased the risk of operator mis-judgement resulting in screw placement failure. Assessment of the relationship between the trans-mammillary vertical line and the pedicle represents a simple method to predict abnormal morphology of the superior articular process before surgery.

Robot-Assisted Thoracolumbar Fixation After Acute Spinal Trauma: A Case Series.

Pedicle screw fixation has become the workhorse for the stabilization of the thoracolumbar spine. Since accurate pedicle screw placement is necessary for a successful surgery, three-dimensional navigation has become a mainstay for placing pedicle screws. However, the published studies have an overrepresentation of lumbar screws despite the prevalence of thoracic fractures. Furthermore, no robotic-assisted pedicle screw study has focused solely on traumatic fractures. The goal of this study was to address whether (1) robot-assisted pedicle screw placement had comparable accuracy in the thoracic and thoracolumbar region and (2) robot-assisted spine surgery was feasible in an acute, traumatic setting. We performed 14 consecutive, thoracolumbar spinal stabilization procedures in which 126 pedicle screws were placed using the Globus ExcelsiusGPS® spine robot in an acute, traumatic setting. Operative times were measured, and the accuracy of pedicle screws was assessed with the Gertzbein and Robbins classification system by two board-certified neuroradiologists. A total of 60-thoracic (T3-T11), the 24-thoracolumbar junction (T12-L1), 40-lumbar (L2-L5), and two-sacral pedicle screws were placed. Pedicle screw placement was accurate with a < 1% (1/126) pedicle breach rate. Thoracolumbar robotic spine surgery in an acute, traumatic setting was demonstrated to have a good safety profile with only one minor neurological deficit which was related to positioning. Furthermore, surgical times were inversely related to the case number. These results together suggest that robot-assisted spine surgery is accurate in the thoracic spine. Furthermore, placement of thoracolumbar screws in an acute trauma is non-inferior to other methods when based on accuracy.

C1-C2 Facet Joint Penetration by C2 Pedicle Screws: Influence of Local Anatomy, Bone Mineral Density, and Screw Length.

A challenge of C2 pedicle screw placement is to avoid penetration into the C1-C2 facet joint, as this may alter normal biomechanics and accelerate joint degeneration. Our objective was to clarify how local anatomy and surgical technique may relate to C2 pedicle screw penetration into the C1-C2 facet joint. C2 pedicle screws were inserted using a fluoroscopically assisted freehand technique. Independent fellowship-trained spine surgeons blindly reviewed intraoperative fluoroscopic and postoperative computed tomography (CT) images for evidence of facet joint penetration (FJP). C2 pedicle morphometry, the sagittal angle of the facet joint, axial and sagittal pedicle screw angles, and screw length were measured on the relevant CT images. A total of 34 patients fulfilled the study criteria, and a total of 68 C2 pedicle screws were placed. Eight screws (16%) penetrated the C1-C2 facet joint. The mean sagittal angle of the C1-C2 facet joint was significantly lower in the FJP group compared with the non-FJP group. The mean sagittal angle of the screws was significantly higher in the FJP group compared with the non-FJP group. The mean screw length was significantly greater for screws causing FJP compared with the non-FJP group. The mean axial screw angle was significantly lower in the FJP group compared with the non-FJP group. Pedicle width, length, height, and transverse angle were not significantly associated with FJP. Independent reviewers were able to identify FJP on intraoperative fluoroscopic imaging in 2 out of 8 cases. Lower sagittal angle of the facet joint, higher sagittal angle of the pedicle screw, and screw length >24 mm are associated with higher risk of C1-C2 FJP. When placing C2 pedicle screws under these conditions, caution should be taken to avoid FJP. Several anatomical and technical factors may increase the risk of C1-C2 FJP during placement of C2 pedicle screws using a fluoroscopically assisted freehand technique, underscoring the importance of preoperative planning and limiting screw length.

Imaging study on the safety of axial pedicle screw placement by the position of the screw trajectory tip on the anteroposterior and lateral radiographs

Objective: To propose a method to judge the safety of axial pedicle screw placement based on the position of the tip of the screw trajectory on the anteroposterior and lateral X-ray radiographs. Methods: The cervical CT data of 40 patients admitted to the Second Affiliated Hospital of Wenzhou Medical University from December 2020 to December 2021 were selected, including 24 males and 16 females, with a mean age of (47.6±13.2) years. Based on the three-dimensional model reconstruction of Mimics software and its function of X-ray, the transmission of the axial pedicle screw and its anteroposterior and lateral films was simulated. The position of the tip of the simulated screw trajectory was divided into 5 regions (regions Ⅰ-Ⅴ) from the inside to the outside on the anteroposterior virtual radiographs, and the upper and lower regions (regions a, b) on the lateral virtual radiographs. By adjusting the direction of the screw, the tip of the screw was located in the corresponding 10 regions (80 screws in each area) on the virtual projections of the anteroposterior and lateral virtual radiographs respectively, and its accuracy was analyzed by CT to determine whether each screw penetrated the medial wall of the pedicle or vertebral artery foramen. The anteroposterior and lateral X-rays and postoperative CT data of 34 patients who underwent axial pedicle screw placement (67 axial pedicle screws were placed in total) from January 2014 to December 2021 were collected, including 18 males and 16 females, with a mean age of (45.8±14.1) years. The position of the tip of the screw trajectory on the anteroposterior and lateral films was divided in the same way. The number of screws in the corresponding 10 positions was counted, and CT analysis was used to determine whether each screw penetrated the medial wall of the axial pedicle or the vertebral artery foreman. Results: The results of the imaging simulation screw placement study showed that the perforation rate of the vertebral artery foramen in region Ⅳ and Ⅴ was 75.0% (120/160) and 100% (160/160), respectively, while the perforation rate of the medial wall of the axial pedicle in the region Ⅰ was 85.6%(137/160). The failure rate in regions Ⅱ and Ⅲ was relatively lower, and the performance of simulated screws located in the region a was better than those in region b. The perforation rates of the medial wall in regions (a-Ⅱ) and (a-Ⅲ) was 7.5% (6/80) and 0 (0/80), respectively, and the perforation rates of the vertebral foramen was 0 (0/80) and 21.3% (17/80), respectively. The retrospective imaging study also showed a higher rate of placement failure in regions Ⅰ, Ⅳ and Ⅴ, and relatively lower in regions Ⅱ and Ⅲ. There were total of 15 screws in region a-Ⅱ and a-Ⅲ, and no destruction of the medial wall of the axial pedicle and the vertebral artery foreman occurred there. Conclusions: Regions a-Ⅱ and a-Ⅲ are the "safety areas" of the tip of the pedicle screw trajectory in the axial vertebra. By analyzing the tip of the pedicle screw trajectory on the anteroposterior and lateral radiographs, the operator can determine the reasonable trajectory of axial pedicle screw placement, prevent the injury of the cervical spinal cord and vertebral artery, and reduce the risk of operation.