Pedicle Screw Placement Research Articles

Mazor X Stealth Robotic Technology: A Technical Note

Minimally invasive techniques in spine surgery have continued to advance as robotic technology has evolved over several generations. Although traditional techniques for placing pedicle screws are still widespread in practice, newer technology has increased the reliability of accurately placing instrumentation with smaller incisions and subsequent decreased length of stay. Additionally, advancements in planning software have improved the ability to align posterior instrumentation to assist with rod placement on multilevel constructs. This paper describes the surgical techniques and operative workflow for placing pedicle screws with the latest robotic technology. The robotic platform, registration, surgical planning, and placement of instrumentation are discussed in detail. Advantages of the Mazor X Stealth Edition compared with the previous generation robot include obviating the need for K wires and eliminating the need for a percutaneous pin, as navigation is integrated into the robot. Our use of this new technology has been encouraging. Using the techniques described in this paper, the first 90 pedicle screws placed with the Mazor X Stealth Edition robot yielded 100% grade A accuracy on the Gertzbein-Robbins scale confirmed on immediate postoperative CT. There were no complications experienced in any case. In our experience, this robotic technology has the potential to improve patient outcomes and is associated with advanced surgical planning compared with more traditional techniques.

Surgeons' Learning Curve of Renaissance Robotic Surgical System.

A few articles on robot-assisted pedicle screw placement described the learning curve but failed to report on the overall operative time, including cases in which the robotic system malfunctioned. The purpose of this study was to identify a single surgeon's learning curve including estimated blood loss, surgery time, anesthesia time, robot time, and complications. A retrospective study was performed between January 2016 and August 2018 for patients who underwent posterior spinal fusion using the Mazor robot. Based on the charts, the robot time, time of anesthesia, and surgery time were recorded, as were the complications, misplacement of screws, and blood loss. Of 62 robot-assisted surgeries scheduled, only 46 were performed (74.2%) upon patients with a mean age of 63.3 ± 13.0 years. The mean follow-up time was 13.2 ± 8.0 months and most commonly a fusion from L4 to S1 was performed (20/46, 43.5%). A high improvement in estimated intraoperative blood loss was observed of 755.7 ± 344.7 mL (slope = -9.89). A decrease in time in anesthesia, surgery, and robotic usage was identified with a slope factor of -3.64 (R 2 = .22, SE = 85.4, P < .005), -3.97 (R 2 = 0.30, SE 75.8, P < .005), -0.69 (R 2 = .07, SE = 27.8, P < .09), respectively. Furthermore, a decrease in pedicle screw insertion time and operative time was found (slope = -0.05, R 2 = .02, SE = 3.4, P = .37). In total, 5 major complications (cases 8, 19, 21, 35, 43) and 6 minor complications (cases 4, 14, 15, 20, 29), were identified (21.7%) without any learning curve. Robot pedicle screw insertion shows no major learning curve; however, the blood loss and the installation process of the system improved with experience. 3.

Transpedicular Screw Placement Accuracy Using the O-Arm Versus Freehand Technique at a Single Institution.

Study Design:Retrospective cohort.Objective:The objective of this study was to assess the effectiveness of the O-arm as an intraoperative imaging tool by comparing accuracy of pedicle screw placement to freehand technique.Methods:The study comprised a total of 1161 screws placed within the cervical (n = 187) thoracic (n = 657), or lumbar (n = 317) spinal level. A pedicle breach was determined by any measurable displacement of the screw outside of the pedicle cortex in any plane on postoperative images. Each pedicle screw was subsequently classified by its placement relative to the targeted pedicle. Statistical analysis was then performed to determine the frequency and type of pedicle screw mispositioning that occurred using the O-arm versus freehand technique.Results:A total of 155 cases (O-arm 84, freehand 71) involved the placement of 454 pedicle screws in the O-arm group and 707 pedicle screws in the freehand group. A pedicle breach occurred in 89 (12.6%) screws in the freehand group and 55 (12.1%) in the O-arm group (P = .811). Spinal level operated upon did not influence pedicle screw accuracy between groups (P > .05). Three screws required revision surgery between the 2 groups (O-arm 1, freehand 2, P > .05). The most frequent breach type was a lateral pedicle breach (O-arm 22/454, 4.8%; freehand 54/707, 7.6%), without a significant difference between groups (P > .05).Conclusions:The use of the O-arm coupled with navigation does not assure improved transpedicular screw placement accuracy when compared with the freehand technique.

A finite element analysis of different pedicle screw placement strategies for treatment of Lenke 1 adolescent idiopathic scoliosis: which is better?

Objective To simulate the process of curve correction with different strategies of pedicle screws placement, and then explore the ideal strategy. Materials and methods: A three-dimensional model was constructed using CT data from a Lenke 1 AIS patient for finite element analysis. Five screw-placement strategies were designed, including collocation of consecutive, interval and alternate screws instrumentation in convex or concave side. The whole surgical procedures of screw-placement strategies were simulated. And their influences in the curve correction as well as the biomechanics of the implants and implant–bone interface were analyzed. Results: The densities of pedicle screws were 100%, 79%, 64%, 57% and 50%, respectively. During curve correction, interval and alternate screws instrumentation demonstrated higher screws stress, while the higher rods and screw–rod interface was observed in consecutive screws instrumentation. When it referred to the interaction force between screws and vertebrae, a lower stress was observed in in consecutive screws instrumentation. After the fixation of rod at convex side, the maximum stress on screws in each strategy was observed in interval screws instrumentation. The higher stress of rods was observed in alternate screws instrumentation in both sides. However, the correction rate of each strategy was similar. Conclusion: There was little distinction on the curve correction rate in different screw-placement strategies. The screw-placement strategy with interval and alternate screws instrumentation has better biomechanics properties than others, except for higher maximum interaction force between screws and vertebrae.

Comparison of robot-assisted and freehand pedicle screw placement for lumbar revision surgery.

The accuracy of robot-assisted pedicle screw implantation is a safe and effective method in lumbar surgery, but it still remains controversial in lumbar revision surgery. This study evaluated the clinical safety and accuracy of robot-assisted versus freehand pedicle screw implantation in lumbar revision surgery. This was a retrospective study. From January 2018 to December 2019, 81 patients underwent posterior lumbar revision surgery in our hospital. Among them, 39 patients underwent revision surgery performed with robot-assisted pedicle screw implantation (Renaissance robotic system), whereas the remaining 42 patients underwent traditional freehand pedicle screw implantation. All patients underwent magnetic resonance imaging (MRI), computed tomography (CT), and X-ray before revision surgery. The sex, age, body mass index, bone mineral density, operative time, blood loss, operative segments, intra-operative fluoroscopy time, and complications were compared between the two groups. The accuracy of pedicle screw implantation was measured on CT scans based on Gertzbein Robbins grading, and the invasion of superior level facet joint was evaluated by Babu's method. There was no statistical difference about the baseline between the two groups (P > 0.05). Although there were no significant differences in operative time and complications between the two groups (P > 0.05), the robot-assisted group had significantly less intra-operative blood loss and shorter intra-operative fluoroscopy times than the freehand group (P < 0.05). In the robot-assisted group, a total of 267 screws were inserted, which were marked as grade A in 250, grade B in 13, grade C in four, and no grade D or E in any screw. In terms of invasion of superior level facet joint, a total of 78 screws were inserted in the robot-assisted group, which were marked as grade 0 in 73, grade 1 in four, grade 2 in one, and grade 3 in zero. By comparison, 288 screws were placed in total in the freehand group, which were rated as grade A in 251, grade B in 28, grade C in eight, grade D in one, and no grade E in any screw. A total of 82 superior level facet joint screws were inserted in freehand group, which were marked as grade 0 in 62, grade onein 18, grade 2 in two, and grade 3 in zero. The robot-assisted technique was statistically superior to the freehand method in the accuracy of screw placement (P < 0.05). Compared with freehand screw implantation, in lumbar revision surgery, the Renaissance robot had higher accuracy and safety of pedicle screw implantation, fewer superior level facet joint violations, and less intra-operative blood loss and intra-operative fluoroscopy time.

Comparison of Accuracy and Clinical Outcomes of Robot-Assisted Versus Fluoroscopy-Guided Pedicle Screw Placement in Posterior Cervical Surgery.

Study Design:This was a prospective controlled study.Objective:To compare the accuracy and clinical outcomes of robot-assisted (RA) and fluoroscopy-guided (FG) pedicle screw placement in posterior cervical surgery.Methods:This study included 58 patients. The primary outcome measures were the 1-time success rate and the accuracy of pedicle screw placement according to the Gertzbein-Robbins scales. The secondary outcome measures, including the operative time, intraoperative blood loss, hospital stay, cumulative radiation time, radiation dose, intraoperative advent events, and postoperative complications, were recorded and analyzed. The Japanese Orthopedics Association (JOA) scores and Neck Disability Index (NDI) were used to assess the neurological function of patients before and at 3 and 6 months after surgery.Results:The rate of grade A was significantly higher in the RA group than in the FG group (90.6% and 71.1%; P < .001). The clinically acceptable accuracy was 97.2% in the RA group and 90.7% in the FG group (P = .009). Moreover, the 1-time success rate was significantly higher in the RA group than in the FG group. The RA group had less radiation time (P < .001) and less radiation dose (P = .002) but longer operative time (P = .001). There were no significant differences in terms of intraoperative blood loss, hospital stay, intraoperative adverse events, postoperative complications, JOA scores, and NDI scores at each follow-up time point between the 2 groups.Conclusions:The RA technique achieved higher accuracy and 1-time success rate of pedicle screw placement in posterior cervical surgery while achieving comparable clinical outcomes.

Anatomical study on the feasibility of a new self-guided pedicle tap

To evaluate the accuracy and safety of pedicle screw placement using a new self-guided pedicle tap. According to the anatomical characteristics of the pedicle, a new self-guided pedicle tap was developed. Six adult spinal specimens including 4 males and 2 females were selected and tapped thread on the right and left sides of each pair of pedicles from the same segment T1 to L5 with traditional taps (control group) and new self-guided pedicle taps (experimental group), respectively. And the pedicle screws were placed. The screwing time was recorded and compared between two groups. CT scanning was completed to observe the accuracy and safety of the screw placement according to the Heary classification of imaging results. The screwing time of thoracic and lumbar vertebrae in the experimental group were (5.87±1.25) min and(5.45±1.67) min, respectively. While those in the control group were (6.12±1.69) min and (6.22±2.13) min, respectively. Then there was no significant difference in screwing time of thoracic and lumbar vertebrae between two groups (P>0.05). The Heary grade of the pedicle screw showed that Heary gradeⅠand Heary gradeⅠ+Ⅱwere respectively 86 (84.31%) and 96 (94.12%) in the experimental group, 72 (71.29%) and 84 (83.17%) in control group, and the difference between two groups was statistically significant (P<0.05). The new self-guided pedicle tap can accurately and safely insert the thoracolumbar pedicle screw, with low cost, easy operation, and good clinical application value.

A novel fluoroscopy-based robot system for pedicle screw fixation surgery.

Robot-assisted pedicle screw insertion has gained popularity in the spinal surgery field. Due to high cost, these spinal robots are not extensively applied in clinical surgeries. Developing an effective robot system with low cost and high clinical acceptability is one of the future trends. We developed a novel fluoroscopy-based robot system for pedicle screw insertion. Four live pigs were conducted with percutaneous pedicle screw insertion. Robot-assisted surgery was performed on the left side of pedicle, while the right opposite side is placed by freehand. The respect accuracy, surgical time and fluoroscopy time were recorded. Robot-assisted group achieved 100% (23/23) accuracy. The average times (6.4 ± 1.7) for intraoperative fluoroscopy usage per procedure were lesser than freehand group (12.5 ± 3.6), and the surgical time (6.8 ± 2.1 min) per screw was reduced compared with freehand group (12.1 ± 4.8 min). Our robot system is cost-effective and feasible for pedicle screw placement. Low economic cost makes it easier for extensive application in primary hospitals.

Treatment of degenerative scoliosis with oblique lateral lumbar interbody fusion combined with long-segment internal fixation through navigation for posterior

To assess the early clinical effects of oblique lateral lumbar interbody fusion (OLIF) combined with posterior long-segment internal fixation through O-arm CT navigation for the treatment of degenerative scoliosis. The clinical data of 15 patients with degenerative scoliosis treated by OLIF combined with posterior long-segment internal fixation through O-arm CT navigation between April 2016 and December were retropectively analyzed. There were 3 males and 12 females, aged from 55 to 73 years old with an average of (62.2±5.3) years. The operation time, intraoperation blood loss, the rate of excellentand good of pedicle screw placement, and complications were recorded. Before surgery, 1 week after surgery and at the final follow-up, the visual analogue scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate the patients' clinical symptoms;standing X-ray film, lumbar spine CT examination was performed at 6 months after surgery to observe coronal scoliosis Cobb angle, lumbar lordosis (LL), intervertebral space height, sagittal vertical axis (SVA), intervertebral fusion, etc. The mean operation time and intraoperative blood loss were respectively (98.7±16.8) min and (50.2±10.7) ml in OLIF surgery, while were (101.5±23.4) min and (63.1±19.7) ml in the surgery of posterior long segment internal fixation. The total mean operation time and intraoperative blood loss were (200.2±40.2) min and (113.3±30.4) ml. All patients were followed from 12 to 25 months with an average of (16.5±5.3) months. Low back pain VAS, lower limb pain VAS and ODI reduced from preoperative (6.8±1.6), (6.2±1.1) scores and (64.6±10.4)% to (1.4±1.0), (1.0±0.5) scores, and (15.8±4.5)% at the final follow-up, the differences were statistically significant(P<0.05). Coronal scoliosis Cobb angle and SVA decreased from preoperative (20.3±13.5)°, (42.3±16.5) mm to (5.5±3.1)°, (25.1±10.9) mm at the final follow-up, and the differences were statistically significant (P<0.05). LL and intervertebral space height increased from preoperative (25.8±8.2)°, (5.9±2.7) mm to (39.3±9.1)°, (10.9±1.2) at the final follow-up, and the differences were statistically significant(P<0.05). Total 240 nails were placed through O-arm CT navigation with the rate of excellent and good of 96%(230/240). Six months after operation, CT of lumbar spine showed interbody fusion of bone. One patient developed anterior medial pain in the left thigh, and two patients experienced transient lefthip flexion after surgery, both of whom recovered during subsequent follow-up. The early clinical effect of oblique lateral lumbar interbody fusion combined with posterior long segment internal fixation through O-arm CT navigation is satisfactory in treatment of degenerative scoliosis. It has the advantages of minimal invasion, accurate navigation of nail placement, high bone fusion rate and few complications. It can provide new options for minimally invasive treatment of degenerative scoliosis.

Safety and accuracy of robot-assisted placement of pedicle screws compared to conventional free-hand technique: a systematic review and meta-analysis

BACKGROUND CONTEXTThe introduction and integration of robot technology into modern spine surgery provides surgeons with millimeter accuracy for pedicle screw placement. Coupled with computer-based navigation platforms, robot-assisted spine surgery utilizes augmented reality to potentially improve the safety profile of instrumentation. PURPOSEIn this study, the authors seek to determine the safety and efficacy of robotic-assisted pedicle screw placement compared to conventional free-hand (FH) technique. STUDY DESIGN/SETTINGWe conducted a systematic review of the electronic databases using different MeSH terms from 1980 to 2020. OUTCOME MEASURESThe present study measures pedicle screw accuracy, complication rates, proximal-facet joint violation, intraoperative radiation time, radiation dosage, and length of surgery. RESULTSA total of 1,525 patients (7,379 pedicle screws) from 19 studies with 777 patients (51.0% with 3,684 pedicle screws) in the robotic-assisted group were included. Perfect pedicle screw accuracy, as categorized by Gerztbein-Robbin Grade A, was significantly superior with robotic-assisted surgery compared to FH-technique (Odds ratio [OR]: 1.68, 95% confidence interval [CI]: 1.20–2.35; p=.003). Similarly, clinically acceptable pedicle screw accuracy (Grade A+B) was significantly higher with robotic-assisted surgery versus FH-technique (OR: 1.54, 95% CI: 1.01–2.37; p=.05). Furthermore, the complication rates and proximal-facet joint violation were 69% (OR: 0.31, 95% CI: 0.20–0.48; p<.00001) and 92% less likely (OR: 0.08, 95% CI: 0.03–0.20; p<.00001) with robotic-assisted surgery versus FH-group. Robotic-assisted pedicle screw implantation significantly reduced intraoperative radiation time (MD: −5.30, 95% CI: −6.83–3.76; p<.00001) and radiation dosage (MD: −3.70, 95% CI: −4.80–2.60; p<.00001) compared to the conventional FH-group. However, the length of surgery was significantly higher with robotic-assisted surgery (MD: 22.70, 95% CI: 6.57–38.83; p=.006) compared to the FH-group. CONCLUSIONThis meta-analysis corroborates the accuracy of robot-assisted pedicle screw placement.

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

Study DesignRetrospective review.PurposeTo 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 LiteratureThe 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.MethodsPatients 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.ResultsA 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.ConclusionsThe 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.

3D-printed navigation template in cervical spine fusion: a systematic review and meta-analysis.

To explore the effectiveness and advantage of three-dimensional (3D)-printed navigation templates (3DPN-template) assisted in cervical spine fusion (CSF) surgery as compared to conventional surgery. An electronic literature search in PubMed, Scopus, Web of Science, and Cochrane was conducted for studies of 3DPN-templates in CSF up to May 2020. Outcome measures as the accuracy rate, operation time, intra-operative blood loss, and fluoroscopy used, associated with CSF were extracted. Mean difference based on changes was quantified using Hedges' g. From 4414 potentially relevant studies, 61 full-text publications were screened. Thirteen studies comprising 330 cases with 1323 screw placements were eligible for inclusion. For template group, pooled estimates were as follows: 97.3% accuracy rate for screw placement, 144.7min for operating time, 273.6ml for blood loss, and 3.2min for fluoroscopic times. A significantly positive difference was observed between the template group compared to control group in terms of accuracy rate of screw placement (Z = 5.3), operation time (Z = 2.41), intra-operative blood loss (Z = 2.64), and fluoroscopic times (Z = 3.64) (all, P value < 0.0001). Risk of bias for studies under review was assessed using the Newcastle-Ottawa Scale (NOS), and 11 studies were found as having high quality. Overall, funnel plot and Begg's test did not indicate obvious publication bias. The 3D-printed navigation template in the cervical surgery can improve accuracy of pedicle screw placement and consequently improve outcomes. In future, multi-center efforts are needed to validate the relationships found in this review.

3D-imaging in percutaneous spine surgery using the Surgivisio system

The Surgivisio system is a new generation of intraoperative 3D imaging, used in our institution for pedicle insertion in minimally invasive spine surgery since January 2018. The purpose of this technical note is to describe the Surgivisio system, its advantages and its limitations, in percutaneous spinal surgery. Results of the first year of use were analyzed, in a series of 29 patients, to evaluate accuracy of pedicle screw insertion, operative time and radiation exposure. On the Heary and Gertzbein classifications, 95.5% of pedicle screw placements (107/112) were rated as acceptable. Mean operative time was 29.3min per vertebra; mean radiation exposure per vertebra was 0.61 mSv. The Surgivisio system is an effective navigation tool for pedicle screw insertion in minimally invasive spinal surgery, with acceptable radiation exposure and operative time for each navigated vertebra. Level of evidenceII, prospective cohort study.

The effect of simulation training on resident proficiency in thoracolumbar pedicle screw placement using computer-assisted navigation.

Residency work-hour restrictions necessitate efficient, reproducible training. Simulation training for spinal instrumentation placement shows significant benefit to learners' subjective and objective proficiency. Cadaveric laboratories are most effective but have high cost and low availability. The authors' goal was to create a low-cost, efficient, reproducible spinal instrumentation placement simulation curriculum for neurosurgery and orthopedic surgery residents using synthetic models and 3D computer-assisted navigation, assessing subjective and objective proficiency with placement of thoracolumbar pedicle screws. Fifteen neurosurgery and orthopedic surgery residents participated in a standardized curriculum with lecture followed by two separate sessions of thoracolumbar pedicle screw placement in a synthetic spine model utilizing 3D computer-assisted navigation. Data were collected on premodule experience, time and accuracy of screw placement, and both subjective and objective ratings of proficiency. Fifteen of 15 residents demonstrated improvement in subjective (Physician Performance Diagnostic Inventory Scale [PPDIS]) and 14 in objective (Objective Structured Assessment of Technical Skills [OSATS]) measures of proficiency in navigated screw placement with utilization of this curriculum (p < 0.001 for both), regardless of the number of cases of previous experience using thoracolumbar spinal instrumentation. Fourteen of 15 residents demonstrated decreased time per screw placement from session 1 to session 2 (p = 0.006). There was no significant difference in pedicle screw accuracy between session 1 and session 2. A standardized curriculum using synthetic simulation training for navigated thoracolumbar pedicle screw placement results in significantly improved resident subjective and objective proficiency. Development of a nationwide competency curriculum using simulation training for spinal instrumentation placement should be considered for safe, efficient resident training.

Comparison of Navigated versus Fluoroscopic-Guided Pedicle Screw Placement Accuracy and Complication Rate

Accurate placement of the pedicle screw is requisite for any successful spinal instrumentation procedure. Screw insertion can be achieved using free-hand and fluoroscopic- or navigation-guided techniques. We sought to assess the variation in accuracy between fluoroscopic- and navigation-guided techniques, which are both used in Sheffield Teaching Hospitals National Health Service Trust, a tertiary spine referral center. Using a retrospective study design, we assessed all the pedicle screws placed between 2013 and 2018. Radiographic and clinical assessment of all cases was performed. We studied 176 spinal instrumented cases, with a total of 831 screws implanted, out of which 296 (35.6%) were navigated and 535 (64.4%) were fluoroscopic guided. Pathology treated included spinal stenosis, spondylolisthesis, tumors, and trauma. Suboptimal screw position was identified in 2.03% (n= 6) of the navigation-guided series and 4.11% (n= 22) of the fluoroscopic-guided series with an overall screw misplacement rate of 3.4%. Evaluating surgeons' individual accuracy rates revealed that suboptimal screw placement registered a higher variation for the fluoroscopy-guided technique, and the misplacement rate was higher for surgeons with a lower volume of cases. Use of navigation during spinal instrumentation helps lower the rate of screw misplacement for spinal surgeons who are at the beginning of their learning curve or do not frequently perform this kind of procedure. Navigation-guided spinal instrumentation is more accurate compared with fluoroscopic-guided techniques and appears to have a lower complication rate.

P15. Power-assisted pedicle screw placement decreases screw wobble

P15. Power-assisted pedicle screw placement decreases screw wobble

231. The use of fusion mass screws in revision spinal deformity surgery: preliminary results and analysis

BACKGROUND CONTEXT Revision spinal deformity surgery in a previously fused spine often presents a number of challenges. Conventional landmarks for pedicle screw placement may be obscured or nonexistent, increasing the potential for inadequate fixation and spinal cord or nerve root injury. In these situations, screws through an existing fusion mass in patients with prior spinal fusion represent an alternative to pedicle screw fixation. This may provide stable fixation while reducing the risk of complications related to pedicle screw placement. PURPOSE To further elucidate the safety and efficacy of fusion mass screws (FMS) in revision spinal deformity surgery as an alternative and/or adjunct to pedicle screw fixation. STUDY DESIGN/SETTING Case series. PATIENT SAMPLE Adult patients undergoing revision spinal deformity surgery. OUTCOME MEASURES BMD of fusion mass, AP thickness of fusion mass, presence and degree of canal breach, screw loosening, screw failure, pseudarthrosis. METHODS Fourteen freehand FMSs were placed in six cases of revision adult spinal deformity surgery between 2016 and 2018. All screws were 5 mm in diameter. FMSs were used to save distal levels from fusion, assist in closing a three-column osteotomy, stabilize a Charcot spine with severe degeneration, and achieve fixation in the setting of pedicular dysplasia associated with NF-1. The bone mineral density (BMD) and thickness of the posterolateral fusion mass was assessed on preoperative CT scans at the level of each planned FMS when available. The accuracy of FMS placement and presence of pseudarthrosis were evaluated on postoperative CT scans. RESULTS Fourteen freehand FMSs were placed in six cases of adult spinal deformity. In all cases, FMSs were combined with pedicle screws, at times at the same levels. There were no neurophysiologic alerts observed during FMS placement and no neurologic deficits or complications postoperatively. On postoperative CT, 1/14 screws had a low-grade breach into the canal ( CONCLUSIONS A mature fusion mass consists of a dense, vacant surface for screw fixation. FMSs may be used to achieve stable fixation in revision spinal deformity cases when pedicles are dysplastic and/or normal anatomical landmarks are obscured by an extensive fusion mass. Additionally, FMSs may provide an additional anchor at a level where two pedicle screws are already placed to increase the strength and rigidity of the construct, assist in osteotomy closure, and potentially shorten the construct. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P109. Improvements in screw placement and accuracy with newer generation robotic-assisted minimally invasive instrumented lumbar fusions

BACKGROUND CONTEXT Lumbar fusion techniques continue to evolve to improve patient safety, minimize soft tissue dissection, and increase the reliability and accuracy of pedicle screw placement. Early technical advancements included navigation and robotic assistance with minimally invasive approaches. Current generation robots now have a more robust and stable surgical arm and the ability to scan the entire surgical field to improve reliability and accuracy of pedicle screw placement. PURPOSE The purpose of this study is to determine if improvements from the earlier generation of surgical robots improve reliability and accuracy of pedicle screw placement. STUDY DESIGN/SETTING Comparative observational cohort. PATIENT SAMPLE A consecutive series of patients undergoing minimally invasive instrumented posterolateral fusion by a single surgeon using second generation (2ndGen) versus third generation (3rdGen) robotic guidance. OUTCOME MEASURES Number of screws planned, number of screws executed or abandoned, number of screws placed accurately. METHODS A consecutive series of patients undergoing minimally invasive instrumented posterolateral fusion by a single surgeon using second generation (2ndGen) versus third generation (3rdGen) robotic guidance were identified. Compared to the 2ndGen robot, the 3rdGen robot has a more robust robotic arm and scans the entire surgical field. The planning software remains the same. Data collected included demographics, total fluoroscopy time, number of planned screws, number of executed screws and number of screws executed accurately. Accurate screw placement was defined as screw placement in the planned position and trajectory without a need for repositioning and confirmed with intraoperative fluoroscopy and radiographs. RESULTS There were 70 cases in each group. The groups were comparable in terms of sex distribution, gender and body mass index. Even though there were more single-level cases in the 2ndGen (43, 61%) compared to the 3rdGen group (27, 39%, p=0.009); the mean total fluoroscopy time (58s vs 63s, p=0.739) and mean fluoroscopy time per level (46s vs 40s, p=0.399) were similar between the two groups. There was a statistically significantly higher rate of abandoned screw placements in the 2ndGen group compared to the 3rdGen group (p CONCLUSIONS Newer generation surgical robotic assistance, with a more robust and stable surgical arm and of the ability to scan the entire surgical field led to a lower rate of abandoned screw placements and greater screw accuracy compared to second generation robots. Further studies are needed to determine if these improvements in screw placement and accuracy translate to improved clinical outcomes. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P117. Navigated robotic assistance improves pedicle screw accuracy in minimally invasive surgery of the thoracolumbar spine: 341 patients in a single institution

BACKGROUND CONTEXT As the field of robot-assisted spine surgery continues to progress and grow, radiographic evaluation of pedicle screw accuracy in a surgical setting is of high interest. Advances in medical imaging and technology have improved pedicle screw placement accuracy, from fluoroscope-guided placement to computer-aided navigation. PURPOSE The purpose of this study is to assess the pedicle screw accuracy of 341 consecutive cases in which navigated robotic assistance was used in a private practice clinical setting. STUDY DESIGN/SETTING Retrospective chart review. PATIENT SAMPLE A total of 341 consecutive patients. OUTCOME MEASURES Screw accuracy, screw offset, complications. METHODS A retrospective, Institutional Review Board-exempt review of 341 navigated robot-assisted spine surgery cases was performed at a single private institution. Radiographic evaluation of screw tip and screw tail offset distance and angulation from preoperative plan to actual final placement based on intraoperative computerized tomography (CT) images was analyzed and calculated. Additionally, pedicle screw malposition, reposition and return to operating room (OR) rates were reviewed. A CT-based Gertzbein and Robbins System (GRS) was used to classify pedicle screw accuracy. The GRS system classifies screws with the rating of A or B as accurate, and C, D, or E as inaccurate placement. The accuracy percentage was calculated by dividing the number of accurate screws placed with robotic navigation by the total cohort. RESULTS In the 341 cases analyzed, 1,929 thoracolumbar pedicle screws were placed. Thirty-one screws (6 patients) deviated from robot use due to surgeon discretion. Of the 1,929 pedicle screws inserted by navigated robotic guidance, only .005% (9/1929) were repositioned intraoperatively. The average age was 66.8 years, and 48% of the patients were male. Average body mass index was 29.31 kg/m2. The majority of the surgical diagnoses were degenerative disc disease (248) and adjacent segment disease (72). The average offset from preoperative plan to actual final placement was 1.7±1.3mm from the tip, 1.6±1.0mm from the tail, and 2.0±1.4° of angulation. Based on the GRS CT-based grading, 97.8% (1,886/1,928) screws were graded A or B, 2.0% (40/1,928) screws were graded C, and 0.2% (3/1,928) screws were graded D. A total of three complications that required a return to the OR were reported: interbody removal, deep wound infection, and wound vacuum-assisted closure. None were related to robotic guidance or pedicle screws. CONCLUSIONS This study demonstrated a high level of accuracy (97.8%) in the clinical use of navigated, robot-assisted surgery in 341 cases. FDA DEVICE/DRUG STATUS ExcelsiusGPS (Globus Medical) (Approved for this indication)

P108. Propensity-matched comparison of open, navigated and robotic-assisted TLIF

BACKGROUND CONTEXT Transforaminal Lumbar Interbody Fusion (TLIF) techniques have evolved from open approaches with dissection to the lateral gutters, to navigation to improve pedicle screw placement accuracy, to robotic assistance to further minimize soft tissue dissection. It is unclear if these technologies improve process measures and minimize variability in surgical technique. PURPOSE To determine if Blood Loss, Operative Time and Length of Stay will be lower with less variability with Robotic, followed by Navigated and Open TLIF. STUDY DESIGN/SETTING Propensity matched longitudinal cohort. PATIENT SAMPLE Consecutive series of patients undergoing primary single-level TLIF. OUTCOME MEASURES Blood Loss, Operative Time and Length of Stay. METHODS A consecutive series of patients undergoing primary single-level Robotic-Assisted TLIFs (RA-TLIF, N=40) were propensity matched to patients undergoing Navigated (NavTLIF, N=51) and Open TLIF (OpTLIF, N=44) using age, sex, smoking status, BMI and ASA grade. RESULTS After propensity matching, 34 cases were included in each cohort. OR Time (184±37 vs 197±48 vs 219±50, p=0.007) was lowest and had the least variability in RA-TLIFs followed by NavTLIF and OpTLIF. Length of Stay (1.5±0.9 vs 2.5±1.2 vs 4.2±1.7, p=0.000), estimated blood loss (254±259 vs 325±288 vs 489±328, p=0.004), drain output (234±257 vs 250±137 vs 653±407, p CONCLUSIONS Operative time was lowest and had the least variability in RA-TLIFs followed by NavTLIF and OpTLIF. Length of stay, blood loss, drain output, total visible blood loss, and total volume of blood products transfused was lowest in RA-TLIFs followed by NavTLIF and OpTLIF. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.