Lumbar Pedicle Research Articles

Pedicle screw navigation using surface digitization on the Microsoft HoloLens.

In spinal fusion surgery, imprecise placement of pedicle screws can result in poor surgical outcome or may seriously harm a patient. Patient-specific instruments and optical systems have been proposed for improving precision through surgical navigation compared to freehand insertion. However, existing solutions are expensive and cannot provide in situ visualizations. Recent technological advancement enabled the production of more powerful and precise optical see-through head-mounted displays for the mass market. The purpose of this laboratory study was to evaluate whether such a device is sufficiently precise for the navigation of lumbar pedicle screw placement. A novel navigation method, tailored to run on the Microsoft HoloLens, was developed. It comprises capturing of the intraoperatively reachable surface of vertebrae to achieve registration and tool tracking with real-time visualizations without the need of intraoperative imaging. For both surface sampling and navigation, 3D printable parts, equipped with fiducial markers, were employed. Accuracy was evaluated within a self-built setup based on two phantoms of the lumbar spine. Computed tomography (CT) scans of the phantoms were acquired to carry out preoperative planning of screw trajectories in 3D. A surgeon placed the guiding wire for the pedicle screw bilaterally on ten vertebrae guided by the navigation method. Postoperative CT scans were acquired to compare trajectory orientation (3D angle) and screw insertion points (3D distance) with respect to the planning. The mean errors between planned and executed screw insertion were [Formula: see text] for the screw trajectory orientation and 2.77±1.46 mm for the insertion points. The mean time required for surface digitization was 125±27 s. First promising results under laboratory conditions indicate that precise lumbar pedicle screw insertion can be achieved by combining HoloLens with our proposed navigation method. As a next step, cadaver experiments need to be performed to confirm the precision on real patient anatomy.

The Importance of the Pars Interarticularis as a Landmark for Safe Lumbar Pedicle Screw Placement: Technical Note.

The use of navigational adjuncts for pedicle screw placement has increased in popularity among surgeons with access to this technology. However, it remains important to have a comprehensive understanding of posterior bony element anatomy with respect to the location of the pedicle in order to ensure safe placement of pedicle screws. Proper exposure and identification of the pars interarticularis provide a helpful landmark during pedicle screw placement in order to confirm navigation accuracy and avoid misplaced instrumentation. In this technical note, we highlight the surgical anatomy of the pars interarticularis of the lumbar spine and its relationship to the lateral, inferior, and medial borders of the pedicle using diagrams and cadaveric dissections.

Robotic-Assisted Spine Surgery Using the Mazor XTM System: 2-Dimensional Operative Video.

We demonstrate the setup and workflow of performing robotic spine surgery using the Mazor XTM system (MAZOR Robotics Inc, Orlando, Florida) in this video. An illustrative case was presented, including detailed steps for S2AI screw and lumbar pedicle screw placement using robotic assistance. A step-by-step narration is provided along with discussion of surgical nuances. Robotic spine surgery can be a safe and efficient method for screw placement, which can potentially reduce the risk of screw malposition. Spine surgeons should be familiar with this technology and keep this technique in their armamentarium. There is no identifying information in this video. A patient consent was obtained for publishing of the material included in the video.

Rotational thromboelastometry-guided transfusion during lumbar pedicle subtraction osteotomy for adult spinal deformity: preliminary findings from a matched cohort study.

OBJECTIVESignificant blood loss and coagulopathy are often encountered during adult spinal deformity (ASD) surgery, and the optimal intraoperative transfusion algorithm is debatable. Rotational thromboelastometry (ROTEM), a functional viscoelastometric method for real-time hemostasis testing, may allow early identification of coagulopathy and improve transfusion practices. The objective of this study was to investigate the effect of ROTEM-guided blood product management on perioperative blood loss and transfusion requirements in ASD patients undergoing correction with pedicle subtraction osteotomy (PSO).METHODSThe authors retrospectively reviewed patients with ASD who underwent single-level lumbar PSO at the University of Virginia Health System. All patients who received ROTEM-guided blood product transfusion between 2015 and 2017 were matched in a 1:1 ratio to a historical cohort treated using conventional laboratory testing (control group). Co-primary outcomes were intraoperative estimated blood loss (EBL) and total blood product transfusion volume. Secondary outcomes were perioperative transfusion requirements and postoperative subfascial drain output.RESULTSThe matched groups (ROTEM and control) comprised 17 patients each. Comparison of matched group baseline characteristics demonstrated differences in female sex and total intraoperative dose of intravenous tranexamic acid (TXA). Although EBL was comparable between ROTEM versus control (3200.00 ± 2106.24 ml vs 3874.12 ± 2224.22 ml, p = 0.36), there was a small to medium effect size (Cohen's d = 0.31) on EBL reduction with ROTEM. The ROTEM group had less total blood product transfusion volume (1624.18 ± 1774.79 ml vs 2810.88 ± 1847.46 ml, p = 0.02), and the effect size was medium to large (Cohen's d = 0.66). This difference was no longer significant after adjusting for TXA (β = -0.18, 95% confidence interval [CI] -1995.78 to 671.64, p = 0.32). More cryoprecipitate and less fresh frozen plasma (FFP) were transfused in the ROTEM group patients (cryoprecipitate units: 1.24 ± 1.20 vs 0.53 ± 1.01, p = 0.03; FFP volume: 119.76 ± 230.82 ml vs 673.06 ± 627.08 ml, p < 0.01), and this remained significant after adjusting for TXA (cryoprecipitate units: β = 0.39, 95% CI 0.05 to 1.73, p = 0.04; FFP volume: β = -0.41, 95% CI -772.55 to -76.30, p = 0.02). Drain output was lower in the ROTEM group and remained significant after adjusting for TXA.CONCLUSIONSFor ASD patients treated using lumbar PSO, more cryoprecipitate and less FFP were transfused in the ROTEM group compared to the control group. These preliminary findings suggest ROTEM-guided therapy may allow early identification of hypofibrinogenemia, and aggressive management of this may reduce blood loss and total blood product transfusion volume. Additional prospective studies of larger cohorts are warranted to identify the appropriate subset of ASD patients who may benefit from intraoperative ROTEM analysis.

Early-middle stage effect of percutaneous spinal endoscopic BEIS technique for lumbar spinal stenosis

To explore the clinical early-middle stage clinical effect of percutaneous spinal endoscopic with the technique of Broad Easy Immediate Surgery(BEIS) for lumbar spinal stenosis. The clinical data of 57 patients with lumbar spinal stenosis treated by surgery from June 2015 to June 2016 were retrospectively analyzed, including 32 cases treated by percutaneous spinal endoscopic with the technique of BEIS (minimally invasive group) and 25 cases by posterior approach of lumbar pedicle screws internal fixation and intervertebral disc excision with bone graft fusion surgery (open surgery group). The pre-operative general data such as age, Body Mass Index (BMI) and etc. were analysed and compared. The operation time, intraoperative blood loss, hospitalization time of the two groups were analyzed. Visual analogue score(VAS), Oswestry Disability Index(ODI), Japanese Orthopedic Association Score(JOA) of preoperative and at 1 week, 1 month, 3 months, 6 months after surgery were used to evaluate the clinical outcome of the two group. All the operations were successful and all the patients recovered smoothly without severe complications, all the wounds got good healing. The pain of the lumbar and lower limb had been improved after surgery. All the patients were followed up more than 6 months with an average of(10.65±3.38) months. There was no significant difference in general data such as age, BMI, and etc. between two groups(P>0.05). There were significant differences in VAS, ODI between two groups at 1 week, 1, 3, 6 months after surgery(P<0.05). The postoperative lumbar pain of the minimally invasive group had been better improved than the open surgery group. However, there was no significant difference in JOA between two groups at 1 week, 1, 3, 6 months after surgery(P>0.05). Intraoperative blood loss and hospitalization time of minimally invasive group was less than that of open surgery group. BEIS technique has the advantage of less trauma, less bleeding for lumbar stenosis when compared to open surgery. It can better alleviate the postoperative local lumbar pain, and early-middle clinical effect is equivalent to open surgery, so it can be used as a safe and effective surgical treatment for lumbar spinal stenosis.

Effect of Robot-Assisted Surgery on Lumbar Pedicle Screw Internal Fixation in Patients with Osteoporosis

We sought to compare clinical outcomes of robot-assisted versus conventional freehand fluoroscopy-assisted lumbar pedicle screw insertion in patients with osteoporosis. This study included 80 patients with osteoporosis and lumbar disease treated with pedicle screw internal fixation in the Department of Spine Surgery, Beijing Jishuitan Hospital between June 2016 and July 2018. Patients were randomly assigned to receive either robot-assisted pedicle screw insertion (experimental group) or freehand fluoroscopy-assisted pedicle screw insertion (control group). The accuracy of screw placement was assessed with postoperative computed tomography. Operative time, pedicle screw placement time, radiation exposure to the medical team, and intraoperative blood loss were recorded. A total of 427 pedicle screws were inserted in 80 patients; 202 pedicle screws were placed in the experimental group, and 225 pedicle screws were placed in the control group. The accuracy of screw placement was significantly higher with robot-assisted pedicle screw insertion (98.5% [199/202]) compared with that achieved with the freehand technique (91.6% [206/225]) (P < 0.05). Robot-assisted pedicle screw insertion was associated with reductions in the mean total pedicle screw placement time (27.60 ± 8.58 vs. 32.26 ± 10.48 minutes), radiation exposure to the medical team (2.23 ± 0.62 vs. 3.35 ± 0.80 fluoroscopic images), and intraoperative blood loss (254.75± 115.34 vs. 356.25 ± 141.00 mL; P < 0.05). The meanoperative time did not differ significantly between the groups. Robot-assisted pedicle screw insertion is a more effective surgical option for patients with osteoporosis who present with various spine diseases compared with fluoroscopy-assisted freehand screw placement techniques.

Navigation in lumbar spinal surgery: When is it useful?

Spinal navigation has evolved greatly since its implementation in the mid-1990s and is now widely used in lumbar spine surgery. However, navigation is not yet accepted as astandard technique. In addition to the classic use in lumbar pedicle screw instrumentation, navigation technology, especially in combination with intraoperative 3D imaging, can be applied in awide range of indications and in all lumbar approaches. The technology is particularly helpful in minimally invasive operations. The concept of "total navigation" stands for an efficient use of the technique from skin incision on and aims at complete elimination of radiation exposure for the surgical team. High accuracy and low radiation exposure of the OR team are indisputable advantages of navigated operations, while time savings and economic benefits are yet to be demonstrated. Regular use and standardized workflow are essential for the safe and effective application of lumbar navigation. Currently, lumbar navigation technology is already of great importance, yet the complex technology requires intensive training. With improved user comfort and image quality, spinal navigation will continue to spread in the future.

Minimally Invasive, Stereotactic, Wireless, Percutaneous Pedicle Screw Placement in the Lumbar Spine: Accuracy Rates With 182 Consecutive Screws.

Standard fluoroscopic navigation and stereotactic computed tomography-guided lumbar pedicle screw instrumentation traditionally relied on the placement of Kirshner wires (K-wires) to ensure accurate screw placement. The use of K-wires, however, is associated with a risk of morbidity due to potential ventral displacement into the retroperitoneum. We report our experience using a computer image-guided, wireless method for pedicle screw placement. We hypothesize that minimally invasive, wireless pedicle screw placement is as accurate and safe as the traditional technique using K-wires while decreasing operative time and avoiding potential complications associated with K-wires. We conducted a retrospective review of 42 consecutive patients who underwent a stereotactic-guided, wireless lumbar pedicle screw placement. All screws were placed to provide fixation to a variety of interbody fusion constructs including anterior lumbar interbody fusion, lateral interbody fusion, and transforaminal lumbar interbody fusion. The procedures were performed using the O-arm intraoperative imaging system with StealthStation navigation (Medtronic, Memphis, TN) and Medtronic navigated instrumentation. After placing a percutaneous navigation frame into the posterior superior iliac spine or onto an adjacent spinous process, an intraoperative O-arm image was obtained to allow subsequent StealthStation navigation. Para-median incisions were selected to allow precise percutaneous access to the target pedicles. The pedicles were cannulated using either a stereotactic drill or a novel awl-tipped tap along with a low-speed/high-torque power driver. The initial trajectory into the pedicle was recorded on the Medtronic StealthStation prior to removal of the drill or awl-tap, creating a "virtual" K-wire rather than inserting an actual K-wire to allow subsequent tapping and screw insertion. Accurate screw placement is achieved by following the virtual path as an exact computer-aided design model of the screw traversing the pedicle is projected onto the display and by using audible and tactile feedback. A second O-arm scan was obtained to confirm accuracy of screw placement. A total of 20 women and 22 men (average age = 56 years) underwent a total of 182 pedicle screw placements using the stereotactic, wireless technique. The total breach rate was 9.9%, with a clinically significant breach rate of 0% (defined as >2 mm medial breach or >4 mm lateral breach) and a clinical complication rate of 0%. Wireless, percutaneous placement of lumbar pedicle screws using computed tomography-guided stereotactic navigation is a safe, reproducible technique with very high accuracy rates.

Minimally invasive lumbar pedicle screw fixation using cortical bone trajectory – Screw accuracy, complications, and learning curve in 100 screw placements

Cortical bone trajectory (CBT) is a novel pedicle insertion technique with comparable or superior mechanical properties and reduced invasiveness compared to traditional methods. We describe the screw accuracy, complications, and learning curve associated with CBT use. A prospective cohort study was performed involving 22 patients who underwent lumbar fusion with CBT screw placement. A total of 100 cortical screws were placed. Post-operative CT scans were reviewed to assess the adequacy of screw placement and calculate the incidence of vertebral body and pedicle breaches from cortical screw placement. Technique-related complications were examined. The entire surgical cohort was divided into two groups: early experience (first 11 patients) and late experience (last 11 patients), to study the effect of learning curve on CBT screw placement. Medial pedicle breach was observed in 6/100 cases and lateral vertebral body breach was observed in 1/100 cases. The incidence of durotomy related to the technique was 4.5% (N = 1/22). Post-surgical wound infection was seen in 9.1% of patients (N = 2/22). 66.7% (N = 4/6) of medial pedicle breaches, 100% (N = 1/1) of lateral breaches, 100% (N = 1/1) of CBT technique-related CSF leaks, and 100% (N = 2/2) of wound infections occurred in the early experience phase of our study (p = 0.0945). A shift in surgical technique and greater efficiency over time decreased the incidence of overall complications in the late cohort. The difference, however, did not reach statistical significance. A lateralized starting point for the cortical screw on the pars interarticularis and use of smaller diameter screws resulted in fewer medial pedicle out-fractures and breaches.

Minimally Invasive Lumbar Pedicle Screw Fixation Using Cortical Bone Trajectory: Functional Outcomes.

BackgroundPedicle screw fixation is currently the mainstay technique for lumbar spinal fusion; however, more minimally invasive techniques are available such as cortical screw fixation. Numerous studies have proven biomechanical equivalence or superiority for cortical screws but few studies have examined clinical outcomes in patients. Our study aims to examine functional outcomes, as well as fusion rates, in patients who underwent pedicle screw fixation using a cortical trajectory.MethodsWe retrospectively reviewed prospectively collected functional outcomes data on 10 patients with a degenerative lumbar disease who underwent cortical screw placement by the senior author. Oswestry Disability Index (ODI) and Roland Morris (RM) scoring were calculated preoperatively, at six to 12 weeks and at six to eight months. The Kruskal-Wallis test and Dunn’s multiple comparison were used to analyze differences in scores over time.ResultsWe found that over time, cortical screw fixation resulted in a mean decrease of 27 from the baseline ODI at six to eight months (p = 0.014). Additionally, six out of seven (86%) patients who had at least 12 months of radiographic follow-up showed fusion.ConclusionsCortical screw fixation showed a decrease of 27 from the baseline ODI at six to eight months, which is comparable to changes from the baseline ODI reported in three, recent, large clinical trials examining functional outcomes following traditional pedicle screw fixation.

Design factors of lumbar pedicle screws under bending load: A finite element analysis

Loosening and breakage of lumbar pedicle screw are the most common complications affecting the spinal stability. The design factors of the pedicle screw that may affect the fixation strength under bending load are pitch length, major diameter, thread profiles and geometry.In this study, 84 finite element (FE) models of the pedicle screw were generated having 7 pitch lengths, 3 major diameters, 2 thread profiles and 2 geometries. The assembly of pedicle screw and CT scan based half section FE model of 4th lumbar vertebra was loaded with a 200N force on the screw head which is equivalent to a bending moment of 11Nm.With triangular thread profile and cylindrical geometry, for 300% increase in pitch length (1–4mm), von Mises stress in screw and von Mises strain in bone increased by 65% and 117% respectively, for a 26% decrease in major diameter (7.6mm to 5.6mm) and correlations were proposed among screw stress (r2=0.992) or bone strain (r2=0.986), pitch length and major diameter. Similar correlations were also proposed for trapezoidal thread profile and tapered geometry (r2=0.994 for screw stress and r2=0.986 for bone strain).Hence, a combination of tapered pedicle screw with lower pitch length, higher diameter and trapezoidal thread profile may serve better under bending load for lumbar vertebral implant.

Radiographic outcomes of transosseous intradiscal screw fixation in lumbar reconstruction—Imaging results of an experience with an alternative in fixation of the unexpectedly osteopenic spine

ObjectiveTo present the results of a new alternative in the technique lumbar pedicle screw reconstruction in osteopenic bone. Pedicle screw fixation is compromised in osteopenic bone and adjunct fixation commonly requires incremental technology that can increase cost and risk, and which may not commonly be available. Readily available low cost techniques are desirable. Patients and MethodsThis is a retrospective review of a prospectively accumulated case series of all patients presenting to the senior author’s (DAB) practice for elective lumbar reconstruction at a tertiary spine referral center. All consecutive patients treated by the senior author 2002–2012 who were unexpectedly found to be severely osteopenic at surgery are reported. ResultsIn seventy-four cases with imaging and clinical information available at an average of five years after surgery there was no screw lucency or accelerated disc degeneration observed despite these screws purposefully projecting into the suprajacent disc space within the limits of the construct. No patient had presented for instrumentation-related revision surgery of any sort. ConclusionTransosseous intradiscal screw fixation is a potentially viable alternative in surgical stabilization of the unexpectedly osteopenic lumbar spine.

Optimal cut-off points of lumbar pedicle thickness as a morphological parameter to predict lumbar spinal stenosis syndrome: a retrospective study.

PurposeLumbar spinal stenosis syndrome (LSSS) is induced by factors such as ligamentum flavum hypertrophy, facet joint hypertrophy and disc degeneration. However, the role of lumbar pedicle (LP) in LSSS has yet to be evaluated. We devised a new morphological parameter called the lumbar pedicle thickness (LPT) to evaluate the connection between LSSS and the LP. We hypothesized that the LPT is a major morphological parameter in the diagnosis of LSSS.Patients and methodsThe LPT data were collected from 136 patients diagnosed with LSSS. A total of 99 control subjects underwent lumbar spine magnetic resonance imaging (MRI) as part of a detailed medical assessment. Axial T2-weighted magnetic resonance (MR) images were acquired from all the participants. Using our picture archiving and communication system, we analyzed the thickness of the LP at the level of L5 vertebra on MRI.ResultsThe average LPT was 9.46±1.81 mm in the control group and 13.26±1.98 mm in the LSSS group. LSSS patients showed a significantly greater LPT (P<0.001) than the control group. The receiver operating characteristic (ROC) curve analysis showed an optimal cutoff point of 11.33 mm for the LPT, with 83.8% sensitivity, 83.8% specificity and area under the curve of 0.92 (95% confidence interval [CI], 0.89–0.96).ConclusionA higher LPT was associated with a higher possibility of LSSS, suggesting its importance in the evaluation of patients with LSSS.

Contribution of Dynamic Surgical Guidance to the Accurate Placement of Pedicle Screws in Deformity Surgery: A Retrospective Case Series

We assessed the contribution of a dynamic surgical guidance (DSG) probe in the accurate placement of thoracic and lumbar pedicle screws (PSs) in patients with spinal deformity. A retrospective review was performed of 98 patients (104 procedures) with various spinal deformities, who had received posterior instrumentation with PSs inserted using either DSG or the conventional free-hand (FH) technique. A total of 882 PSs were inserted using DSG (DSG group) and 603 using the FH technique (FH group). The DSG probe was preferably chosen for large osteosyntheses and severe deformities. Two neurosurgeons, unaware of the surgical groups, reviewed all the intraoperative computed tomography scans and assessed all the PS placements. Of the PSs used, 95.4% in the DSG group and 92.2% in the FH group were correctly placed (P= 0.0136). The difference in screw placement accuracy was greater at the thoracic level (DSG group, 92.5%; vs. FH group, 87.0%; P= 0.0310) than at the lumbar level (DSG group, 98.0%; vs. FH group, 95.4%; P= 0.0385). Severe (>4 mm) lateral breaches occurred in 24 cases (4.0%) in the FH group but in only 5 (0.6%) in the DSG group (P < 0.0001). No severe medial breach was observed in either group. Despite having more patients with severe deformities in the DSG group, PS insertion was significantly more accurate with DSG. This technique also reduced the severe unacceptable lateral misplacement rate (>4 mm) and, consequently, the incidence of intraoperative screw revisions even in patients with severe deformities.

Wednesday, September 26, 2018 2:00 PM – 3:00 PM Increasing Value: Lumbar Spine Surgery: 66. Cost-benefit analysis of intraoperative EMG for pedicle screw placement in routine lumbar fusions

BACKGROUND CONTEXT Advances in intraoperative neuromonitoring have increased the safety and shown clear benefit for complex spine cases. However, controversy exists regarding the utility of intraoperative EMG for identification of pedicle wall breaches for uncomplicated posterolateral lumbar fusions. PURPOSE To perform a cost-benefit analysis of pedicle screw stimulation via triggered EMG in routine lumbar pedicle screw cases. STUDY DESIGN/SETTING Prospective case series. PATIENT SAMPLE Patients undergoing primary instrumented posterior lumbar fusion with pedicle screws from L1 to S1. OUTCOME MEASURES EMG screw stimulation, need for screw repositioning, variable direct cost. METHODS A prospective study was conducted at single institution. Patients undergoing instrumented posterolateral lumbar fusion were monitored with intraoperative triggered EMGs. Pedicle screws were placed freehand from L1 to S1 by attending physicians and spine fellows. Concern for pedicle breach was identified with a screw stimulation value less than 10 mA. RESULTS There were 145 cases with a total of 725 pedicle screws placed. Mean age was 57.8±14.2 years, OR time was 238±95 minutes, EBL was 426.8±354.3cc. Mean number of surgical levels fused was 2.7±1.1. 686 (95%) screws stimulated at >10 mA and 39 (5%) screws stimulated at CONCLUSIONS Only 1% of the 725 lumbar pedicle screws placed in 8 of 145 cases required repositioning. Due to the infrequency of pedicle wall breaches and the cost of ION, the utility of this modality in straightforward lumbar fusions should be critically evaluated. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Wednesday, September 26, 2018 1:00 PM – 2:00 PM Navigation and Intraoperative Monitoring: 47. The utility of intraoperative electromyography and computer-assisted navigation for lumbar pedicle screw placement

BACKGROUND CONTEXT Suboptimal pedicle screw placement may cause neurological complications following posterolateral lumbar fusions (PLF). To decrease the risk of these complications, computer-assisted navigation (CAN) and intraoperative neuromonitoring such as electromyography (EMG) are often used during PLF to ensure safe pedicle screw placement. While CAN and EMG can improve the safety of pedicle screw placement, their routine use in PLF remains controversial. No studies have directly compared the risk of neurological complications following pedicle screw placement in PLF with and without CAN or EMG. PURPOSE Evaluate the risk of neurological injuries and risk of reoperation for pedicle screw revision/removal in patients that had PLF with and without computer-assisted navigation and/or intraoperative electromyography. STUDY DESIGN/SETTING Retrospective database study. PATIENT SAMPLE Patients undergoing posterolateral lumbar fusion. OUTCOME MEASURES Neurological injuries and risk of reoperation for pedicle screw revision/removal. METHODS Retrospective longitudinal analyses were performed using the MarketScan databases from 2007 to 2014. Patients undergoing PLF surgery with and without CAN and/or EMG for degenerative lumbar disorders were identified via ICD-9-CM and CPT codes. Exclusion criteria were: age RESULTS From 2007 to 2014, 10,246 patients underwent PLFs (age 60±12 years, 58% female). CAN only was used in 5.5% of patients, EMG only in 20% and CAN and EMG in 0.87% of patients. Overall, CAN only use increased from 2.7% in 2007 to 8.72% in 2014 (p CONCLUSIONS In this retrospective review of national administrative data, we found a steady increase in the use of CAN for PLFs from 2007 to 2014. The risk of neurological complications following primary PLFs is low and the routine use of CAN and/or EMG may not decrease this risk. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Use of the Airo mobile intraoperative CT system versus the O-arm for transpedicular screw fixation in the thoracic and lumbar spine: a retrospective cohort study of 263 patients.

Navigation-enabling technology such as 3D-platform (O-arm) or intraoperative mobile CT (iCT-Airo) systems for use in spinal surgery has considerably improved accuracy over that of traditional fluoroscopy-guided techniques during pedicular screw positioning. In this study, the authors compared 2 intraoperative imaging systems with navigation, available in their neurosurgical unit, in terms of the accuracy they provided for transpedicular screw fixation in the thoracic and lumbar spine. The authors performed a retrospective analysis of clinical and surgical data of 263 consecutive patients who underwent thoracic and lumbar spine screw placement in the same center. Data on 97 patients who underwent surgery with iCT-Airo navigation (iCT-Airo group) and 166 with O-arm navigation (O-arm group) were analyzed. Most patients underwent surgery for a degenerative or traumatic condition that involved thoracic and lumbar pedicle screw fixation using an open or percutaneous technique. The primary endpoint was the proportion of patients with at least 1 screw not correctly positioned according to the last intraoperative image. Secondary endpoints were the proportion of screws that were repositioned during surgery, the proportion of patients with a postoperative complication related to screw malposition, surgical time, and radiation exposure. A blinded radiologist graded screw positions in the last intraoperative image according to the Heary classification (grade 1-3 screws were considered correctly placed). A total of 1361 screws placed in 97 patients in the iCT-Airo group (503 screws) and in 166 in the O-arm group (858 screws) were graded. Of those screws, 3 (0.6%) in the iCT-Airo group and 4 (0.5%) in the O-arm group were misplaced. No statistically significant difference in final accuracy between these 2 groups or in the subpopulation of patients who underwent percutaneous surgery was found. Three patients in the iCT-Airo group (3.1%, 95% CI 0%-6.9%) and 3 in the O-arm group (1.8%, 95% CI 0%-4.0%) had a misplaced screw (Heary grade 4 or 5). Seven (1.4%) screws in the iCT-Airo group and 37 (4.3%) in the O-arm group were repositioned intraoperatively (p = 0.003). One patient in the iCT-Airo group and 2 in the O-arm group experienced postoperative neurological deficits related to hardware malposition. The mean surgical times in both groups were similar (276 [iCT-Airo] and 279 [O-arm] minutes). The mean exposure to radiation in the iCT-Airo group was significantly lower than that in the O-arm group (15.82 vs 19.12 mSv, respectively; p = 0.02). Introduction of a mobile CT scanner reduced the rate of screw repositioning, which enhanced patient safety and diminished radiation exposure for patients, but it did not improve overall accuracy compared to that of a mobile 3D platform.

Electromyography stimulation compared with intraoperative O-arm imaging for evaluating pedicle screw breaches in lumbar spine surgery: a prospective analysis of 1006 screws in 164 patients

Background contextLumbar pedicle screw placement can be technically challenging. Malpositioned screws occur in up to 15% of patients and could result in radiculopathy or instrumentation failure. PurposeTo compare intraoperative electromyography (EMG) and image guidance using an O-arm for identifying pedicle breach during elective lumbar fusion. Study designProspective observational study. Patient sampleAll adult patients undergoing elective lumbar spinal fusion operations for degenerative spine disorders (including adjacent segment degeneration, degenerative scoliosis, and symptomatic spondylosis and spondylolisthesis) at a single institution from July 1, 2014, to December 1, 2015, were prospectively tracked. Outcome measuresPedicle breach. MethodsPedicle screws from L2–S1 were placed using C-arm assisted freehand technique. All screws were stimulated with EMG and evaluated using the O-arm intraoperative imaging system. Electromyography data were compared with intraoperative images to assess the accuracy of identifying pedicle breaches. No funding was received for this work. ResultsOne thousand six lumbar pedicles screws were placed from L2 to S1 in 164 consecutive cases. The mean patient age was 59.2 years. Thirty-five breaches (15 lateral and 20 medial) were visualized with O-arm imaging and confirmed by palpation (3.5% of screws placed). Of the breaches, 14 screws stimulated below the 12-mA threshold, nine screws stimulated between 12 and 20 mA, and 12 screws did not generate an EMG response. Forty screws stimulated below a 12-mA threshold but showed no breach on imaging. Using the 12-mA threshold, the sensitivity of EMG was 40%, specificity was 96%, positive predictive value was 26%, and negative predictive value was 98%. All 35 breached screws were corrected during surgery. There were no postoperative symptoms caused by breached screws and no patients required reoperation. ConclusionsOur findings indicate that EMG may not be a highly reliable tool in determining an anatomical breach during placement of lumbar pedicle screws. O-arm may be better for detecting either medial or lateral breaches than EMG stimulation if there are concerns about screw placement or for confirmation of placement before leaving the operating room.

Mechanomyography for Intraoperative Assessment of Cortical Breach During Instrumented Spine Surgery

We sought to determine the utility of mechanomyography (MMG) in detecting and preventing pedicle breach in instrumented lumbar spine surgery. In a prospective nonrandomized trial without controls, we selected consecutive patients to undergo intraoperative MMG during instrumented lumbar spine surgery. MMG testing was performed at the original pilot hole, after tapping, and after screw placement, with the minimum current to elicit a recorded MMG response. All patients underwent a postoperative computed tomography scan, and a single radiologist interpreted each pedicle to identify breach. Chi-square test was used to compare patients with and without breaches. Two sample Student's t-tests were used to compare changes in functional outcomes. Sensitivity and specificity of MMG were computed using receiver operating characteristic curve analysis. There were 122 consecutive instrumented lumbar surgery patients enrolled, with a total of 890 lumbar pedicle screws tested with MMG. The medial or inferior breach rate was 2.25%, with no statistically significant difference in Oswestry Disability Index or visual analog scale between patients who breached and who did not. For the MMG measurement from the original pilot hole, the area under the receiver operating characteristic was 0.835; the maximum combination of sensitivity (80.42%) and specificity (80.6%) was found using MMG current ≤12 mA. We found that an MMG cutoff of >12 mA resulted in a 99.5% likelihood of no medial or inferior breach. MMG can be safely used during instrumented lumbar spine surgery. A cutoff value of >12 mA for MMG can accurately predict and prevent medial and inferior pedicle screw breach.

Does solid fusion eliminate rod fracture after pedicle subtraction osteotomy in ankylosing spondylitis-related thoracolumbar kyphosis?

Background ContextRod fracture (RF) has a negative impact on the surgical outcome of patients with ankylosing spondylitis (AS) after lumbar pedicle subtraction osteotomy (PSO). However, there is a paucity of published studies analyzing the risk factors for RF in PSO-treated patients with AS with thoracolumbar kyphosis. PurposeThe objective of this study was to investigate the risk factors for RF after PSO for thoracolumbar kyphosis secondary to AS. Study Design/SettingThis is a retrospective single-center study. Patient SamplePatients with AS who underwent PSO for thoracolumbar kyphosis between January 2002 and December 2016 were included. Outcome MeasuresDemographic data, including age, sex, body mass index, and smoking status, were summarized. The surgical data analyzed included the levels of osteotomy, the fusion levels, the upper instrumented vertebra, the lower instrumented vertebra, the osteotomy site, the rod material, the rod diameter, and the rod contour angle (RCA). Radiographic parameters included the sagittal vertical axis, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence. Radiographic parameters were measured at baseline, immediately after the operation, and at the final follow-up. Adequate ossification of the anterior longitudinal ligament (ALL) at the PSO level was defined by a total bony bridge. Adequate ossification of the ALL was also measured at baseline, immediately after the operation, and at the final follow-up. MethodsPatients with a minimum of 2 years' follow-up or patients who developed RF were enrolled in the study. Recruited patients were divided into the RF group and the no-RF group based on whether they developed RF. Patient demographics, operative data, radiographic parameters, and adequate ossification of the ALL were analyzed to determine the risk factors for RF. For patients with RF, the fusion status at the PSO level, the time course to the development of RF, the site of RF, and the corresponding solution were also recorded. ResultsRod fracture occurred in 11 (8.9%) of the 123 recruited patients. Solid fusion at the PSO level was found in all patients in the RF group. The average duration to the onset of RF was 31.4 months (range, 12–68 months). All RFs occurred at or immediately adjacent to the PSO level. The RCA was greater in the RF group than in the no-RF group (27.8° vs 22.9°, p=.031). A greater proportion of patients with a rod diameter of 5.50 mm were found in the RF group than in the no-RF group (100.0% vs 68.8%, p=.033). There was a larger proportion of patients with adequate ossification of the ALL at the final follow-up visit in the no-RF group than in the RF group (67.0% vs 27.3%, p=.018). Multivariate analyses demonstrated that the RCA (odds ratio, 1.174; 95% confidence interval, 1.018–1.354; p=.028) and adequate ossification of the ALL at the final follow-up visit (odds ratio, 0.079; 95% confidence interval, 0.014–0.465; p=.005) were independent factors for RF. Notably, revision surgery was performed among six patients, whereas conservative treatment was used for the remaining five patients. ConclusionsIn patients with AS after PSO for thoracolumbar kyphosis with solid fusion at the PSO level, the incidence of RF was 8.9%. Rod diameter was identified as a risk factor for RF. Furthermore, the RCA was identified as an independent risk factor for RF. In contrast, adequate ossification of the ALL around the PSO level at the final follow-up visit was identified as an independent protective factor for RF.