O-arm Imaging Research Articles

Posterior percutaneous endoscopic cervical foraminotomy and discectomy for degenerative cervical radiculopathy using intraoperative O-arm imaging.

IntroductionPosterior percutaneous endoscopic cervical foraminotomy and discectomy (P-PECD) is a minimally invasive technique for the treatment of degenerative cervical radiculopathy. The O-arm, an intraoperative mobile computed tomography (CT) scanner, may improve spine surgery outcomes.AimTo evaluate clinical outcomes of O-arm assisted P-PECD in patients with degenerative cervical radiculopathy.Material and methodsBetween January 2013 and January 2018, 32 patients with degenerative cervical radiculopathy who underwent P-PECD were followed up for 12 months. Their demographic, clinical and surgical data were reviewed retrospectively. All patients received intraoperative O-arm scanning to assess working cannula placement and decompression. The visual analogue scale (VAS), the neck disability index (NDI), and Odom’s criteria were used to evaluate clinical outcomes.ResultsCompared with preoperative values, mean NDI, neck-VAS, and arm-VAS scores were dramatically improved 1 week postoperatively, and the improvement was maintained for at least a year after surgery (from 27.6 ±10.5, 5.8 ±1.7, and 7.2 ±2.3 to 1.4 ±0.8, 1.1 ±0.8 and 0.9 ±0.6, respectively). According to Odom’s criteria, 27/32 patients (84.4%) reported excellent or good results. There were no permanent complications. One patient suffered from transient thumb weakness due to a cervical nerve root injury caused by the spinal needle.ConclusionsP-PECD aided by intraoperative O-arm imaging is a safe, effective, and minimally invasive procedure for treating degenerative cervical radiculopathy that can provide accurate cannula placement and thorough decompression.

Intraoperative Use of O-arm in Pediatric Cervical Spine Surgery.

Traditionally, fluoroscopy and postoperative computed tomographic (CT) scans are used to evaluate screw position after pediatric cervical spine fusion. However, noncontained screws detected postoperatively can require revision surgery. Intraoperative O-arm is a 3-dimensional CT imaging technique, which allows intraoperative evaluation of screw position and potentially avoids reoperations because of implant malposition. This study's objective was to evaluate the use of intraoperative O-arm in determining the accuracy of cervical implants placed by a free-hand technique using anatomic landmarks or fluoroscopic guidance in pediatric cervical spine instrumentation. A single-center retrospective study of consecutive examinations of children treated with cervical spine instrumentation and intraoperative O-arm from 2014 to 2018 was performed. In total, 44 cases (41 children, 44% men) with a mean age of 11.9 years (range, 2.1 to 23.5 y) were identified. Instability (n=16, 36%) and deformity (n=10, 23%) were the most frequent indications. Primary outcomes were screw revision rate, neurovascular complications caused by noncontained screws, and radiation exposure. A total of 272 screws were inserted (60 occipital and 212 cervical screws). All screws were evaluated on fluoroscopy as appropriately placed. Four screws (1.5%) in 4 cases (9%) were noncontained on O-arm imaging and required intraoperative revision. A mean of 7.7 levels (range, 5 to 13) were scanned. The mean CT dose index and dose-length product were 15.2±6.87 mGy and 212.3±120.48 mGy×cm. Mean effective dose was 1.57±0.818 mSv. There was no association between screw location and noncontainment (P=0.129). No vertebral artery injuries, dural injuries, or neurologic deficits were related to the 4 revised screws. Intraoperative non-navigated O-arm is a safe and efficient method to evaluate screw position in pediatric patients undergoing cervical spine instrumentation. Noncontained screws were detected in 9% of cases (n=4). O-arm delivers low radiation doses, allows for intraoperative screw revision, and negates the need for postoperative CT scans after confirmation of optimal implant position. Level IV.

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.

An initial experience with intraoperative O-Arm for deep brain stimulation surgery: can it replace post-operative MRI?

Deep brain stimulation (DBS) is used to treat movement disorders, severe psychiatric disorders, and neuropathic pain, among other diseases. Advanced neuroimaging techniques allow direct or indirect localization of the target site, which is verified in many centers by the intraoperative recording of unitary neuronal activity. Intraoperative image acquisition technology (e.g., O-Arm) is increasingly used for accurate electrode positioning throughout the surgery. The aim of our study is to analyze the initial experience of our team in the utilization of O-Arm for planning DBS and monitoring its precision and accuracy throughout the procedure. The study included 13 patients with movement disorders. All underwent DBS with the intraoperative O-arm image acquisition system (iCT) and Medtronic StealthStation S7 cranial planning system, placing a total of 25 electrodes. For each patient, we calculated the difference between real and theoretic x, y, z coordinates, using the paired Student's t test to evaluate absolute and directional differences and the one-sample Student's t test to analyze differences in Euclidean distances. No statistically significant differences were found in absolute, directional, or Euclidean distances between intended and actual x, y, and z coordinates, based on iCT scan. Our experience confirms that utilization of the O-Arm system in DBS provides accurate and precise verification of electrode placements throughout the procedure. Recent studies found no significant differences between iCT and postoperative MRI, the current gold standard. Further prospective studies are warranted to test the elimination of postoperative MRI when this system is used.

Intraoperative CT and Surgical Navigation for Iliosacral Screws: Technique for Patients With Sacral Dysmorphism.

Percutaneous iliosacral screw (IS) fixation for pelvic ring injuries with the use of an O-arm imaging system has been associated with decreased procedure time and improved accuracy of IS screw placement compared with the use of fluoroscopic guidance. Specifically, patients with sacral dysmorphism require identification of safe bony sacral corridors, using specific anatomical measurements, to decrease the likelihood of complications such as screw perforation. Intraoperative computed tomography imaging and navigation can aid in safe and accurate IS screw fixation in patients with difficult anatomy.

Application of Multimodal Image Fusion to Precisely Localize Small Intramedullary Spinal Cord Tumors

We sought to study the application of precise intraoperative localization of small intramedullary spinal cord tumors. From November 2015 to August 2017, 5 patients with small intramedullary spinal cord tumors were arranged in this group. By using the O-arm image system, we acquired the intraoperative computed tomography images of all patients and sent them to the Stealth navigation system. Medtronic Synergy Cranial software was used to complete the image fusion with preoperative magnetic resonance images, and the fused images were used to localize the intramedullary spinal cord tumors by the navigation system. The navigation errors were evaluated by measuring the maximum distance between the end of the tumor in sagittal magnetic resonance imaging and its real position. Five patients accomplished the multimodal image fusion, and we successfully completed the image-guided surgeries. The mean diameter of tumors was 12.2 ± 3.1 mm in sagittal magnetic resonance imaging, and the mean incision length was 12.7 ± 3.3 mm. The time of image processing was between 13 minutes and 17 minutes, and the mean value was 15 ± 1.6 minutes. The navigation error was between 0.9 mm and 1.5 mm, and the mean value was 1.2 ± 0.2 mm. The application of the multimodal image fusion combined with intraoperative O-arm image navigation system can be used to localize small intramedullary tumors.

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.

Utilization of the 3D-printed spine model for freehand pedicle screw placement in complex spinal deformity correction.

We aim to demonstrate the safety and efficacy of utilizing 3D-printed spine models to facilitate freehand pedicle screw placement in complex spinal deformity correction. Currently there is no data on using 3D-printed models for freehand pedicle screw placement spinal deformity correction. All patients undergoing spinal deformity correction over a 16-month period (September 2015 - December 2016) at the Spine Hospital of Columbia University Medical Center by the senior surgeon were reviewed. 3D-printed spine models were used to facilitate intraoperative freehand pedicle screw placement in patients with severe spinal deformities. Intraoperative O-arm imaging was obtained after pedicle screw placement in all patients. Screws were graded as intrapedicular, <2 mm breach, 2-4 mm breach, and >4 mm breach; anterior breaches >4 mm were also recorded. Screw accuracy was compared to a historical cohort (not using 3D-printed models) using SPSS 23.0 (Chicago, IL, USA). A total of 513 freehand pedicle screws were placed from T1 to S1 in 23 patients. Overall, 494 screws (96.3%) were placed in acceptable positions according to the pre-operative plan, which had no statistically significant difference (P=0.99) compared to a historical cohort with less severe deformities. There were 84.2% screw that were intrapedicular or <2 mm breach; among the 81 screws (15.8%) with >2 mm breach, 67 were lateral breaches (most are intended juxtapedicular placement), whereas 14 were medial breaches. There were 11 screws (2.1%) that required repositioning due to pedicle violation, and eight screws (1.6%) had >4 mm anterior breach and required shortening. There was no neuromonitoring change or any other complications directly or indirectly related to freehand pedicle screw placement. The 3D-printed spinal model can make freehand pedicle screw placement safer in severe spinal deformity cases with acceptable accuracy, and no neurological or vascular complications.

The Free-Hand Technique for S2-Alar-Iliac Screw Placement: A Safe and Effective Method for Sacropelvic Fixation in Adult Spinal Deformity.

Spinopelvic fixation is an integral part of achieving solid fusion across the lumbosacral junction, especially in deformity procedures requiring substantial correction or long-segment constructs. Traditional S2-alar-iliac (S2AI) screw-placement techniques utilize fluoroscopy, increasing operative time and radiation exposure to the patient and surgeon. We describe a novel free-hand technique for S2AI screw placement in patients with adult spinal deformity. We reviewed the records of 45 consecutive patients who underwent spinopelvic fixation performed with use of S2AI screws by the senior surgeon and various fellows or residents over a 12-month period (2015 to 2016). In each case, the S2AI screws were placed utilizing a free-hand technique without fluoroscopic or image guidance. Screw position and accuracy were assessed by intraoperative O-arm imaging and analyzed using 3-dimensional interactive manipulation of computed tomography images. A total of 100 screws were placed, 51 by the senior surgeon and 49 by trainees. The mean patient age was 57.4 ± 12.7 years at the time of surgery; 37 (82.2%) of the patients were female. Preoperative diagnoses included adult idiopathic scoliosis (n = 19), adult degenerative scoliosis (n = 15), flatback syndrome (n = 2), fixed sagittal imbalance (n = 6), and distal junctional kyphosis (n = 3). Five (5%) of the screws were placed with moderate to severe cortical breaches, all of which perforated the pelvis posteriorly, with no clinically notable neurovascular or visceral complications. The breach rate did not differ significantly between the senior surgeon and trainees. The free-hand technique for S2AI screw placement, when performed in a standardized manner, was demonstrated to be safe and reliable in constructs requiring spinopelvic fixation. The accuracy of screw placement relies on visible and palpable anatomic landmarks that obviate the need for intraoperative fluoroscopy or image guidance, potentially reducing operative time and radiation exposure. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Posterior mediastinal ganglioneuroma:A case report and literature review

ObjectivesGanglioneuroma is a rare, benign neurogenic tumor arising from the sympathetic ganglia.In this report, we reviewed and summarized the clinical features, treatment, and prognosis of a posterior mediastinal ganglioneuroma. CaseHere, we report on a 29-year-old man referred to us with transient pain in the right side of the chest, lasting for three days.Physical examination revealed no abnormalities. The results of routine laboratory tests were within the normal ranges.Thoracic spinal magnetic resonance imaging showed a well-defined, solid mass in the right paravertebral region at the T5-T8 level, measuring 7.5 cm×4.2 cm×1.5 cm.To accurately locate the lesion during surgery, O-arm intraoperative imaging was used in conjunction with the Stealth Station navigation system.The tumor was completely excised and no related complications occurred.The tumor was an encapsulated mass with a solid, homogenous, grayish-tan cut surface.Histopathological examinations confirmed that the mass was a ganglioneuroma. ConclusionsGanglioneuroma is a rare, benign tumor.Prior to treatment, a careful imaging evaluation is necessary in order to obtain an accurate diagnosis.A definitive diagnosis can be made by histological examination.En bloc resection is the preferred treatment for ganglioneuroma as it has an excellent prognosis.

Application of intraoperative O-arm-assisted real-time navigation technique for spinal fixation

This study explored the combined use of the O-arm and real-time navigation during spinal fixation. The clinical data for 60 patients undergoing spinal fixation, at Beijing Tsinghua Chang Gung Hospital between May 5, 2015 and May 1, 2017, were retrospectively analyzed. Pre-, intra-, and postoperative imaging findings were assessed. The patients were classified into the occipitocervical fusion (32 cases) and thoracic/lumbar/sacral spine fixation (28 cases, including 6 cases of percutaneous pedicle screw) groups. Lesion resections were performed microscopically. An O-arm, combined with real-time navigation, was used to assess spinal fixation. Efficacy was evaluated using operative times, X-ray times, screw positioning, and complications. Within the occipitocervical fusion group, 182 screws were placed in the cervical spine and 96 in the occipital bone. However, 6 screws penetrated the bone cortex and were adjacent to the vertebral arteries, based on O-arm three-dimensional imaging; therefore, the precision rate was 96.7%. Within the thoracic/lumbar/sacral spine fixation group, 148 pedicle screws were implanted, with 4 initially outside the vertebral body, yielding a precision rate of 97.3%. Ten percutaneous pedicle screws were implanted and well positioned. O-arm scans were performed 3 times/patient, with an average of 20-30 min/time. Screw implantation times were 5-7 min (cervical spine), 8-10 min (thoracic spine), and 6-8 min (lumbar spine). Intraoperative O-arm scans, combined with real-time navigation technology, allow real-time observation of screw angles and depths, improving the accuracy and safety of posterior screw fixations and reducing the radiation dose and frequency experienced by patients and surgeons.

O-arm with navigation versus C-arm: a review of screw placement over 3 years at a major trauma center

Introduction: There is a relatively high incidence of screw misplacement during spinal instrumentation due to distortion of normal anatomy following spinal trauma. The O-arm is the next-generation spinal navigation tool that provides intraoperative 3-D imaging and navigation for spine surgeries.Aims and objectives: To evaluate and compare the use of O-arm as compared to C-arm for spinal trauma in a Level I trauma center in India.Materials and methods: In this retrospective study over 3 years (July 2010–April 2013), All patients of spinal injury who underwent spinal instrumentation were divided into O-arm group and C-arm group. Accuracy of screw placement was assessed during each surgery in both groups.Results: A total of 587 patients were evaluated during the study period. There were 278 patients in O-arm group and 309 patients in C-arm group. Both groups were well matched in mean age (27.7 vs. 28.9 years), ASIA grades, and level of injury. The number of screws placed was significantly higher in the C-arm group as compared to the O-arm group (2173 vs. 1720). However, the O-arm group had significantly less screw malplacement rate of 0.93% (n = 16) as compared to malplacement rate in C-arm group of 8.79% (n = 191, p < 0.05).Conclusion: Use of O-arm imaging system ensures accurate screw placement and dramatically decreases screw malplacement rate, thus providing better patient safety. Its use is especially beneficial in academic and teaching centers where novice surgeons can attain results equivalent to that of experts in spinal instrumentation.

Stereotactic Accuracy and Surgical Utility of the O-Arm in Deep Brain Stimulation Surgery.

The stereotactic accuracy of intraoperative imaging is critical to clinical outcome, particularly in "asleep" deep brain stimulation (DBS) surgery that typically forgoes neurophysiological techniques. Different intraoperative imaging modalities and associated accuracies have been reported, including magnetic resonance imaging (MRI), computed tomography (CT), and O-arm. To analyze intraoperative O-arm imaging accuracy and to evaluate the utility of microelectrode mapping. O-arm images of DBS electrodes were collected during implantation in the subthalamic nucleus in patients with Parkinson disease. Images were fused to postoperative MRI and postoperative CT scans. Stereotactic coordinates for the electrode tip were measured independently. Radial distances between the images were compared. The impact of microelectrode mapping on final DBS electrode positioning was also evaluated. In 71 consecutive DBS electrodes, the average radial error of the electrode tip between the O-arm and MRI was 1.55 ± 0.58mm. The average radial error between the O-arm and CT was 1.03 ± 0.61mm. Thus, the O-arm images accurately depicted the position of the electrode. However, in 14% of cases, microelectrode mapping revised the DBS electrode position beyond the preoperative direct target in combination with accurate intraoperative imaging. Intraoperative O-arm images reliably and accurately displayed the location of the DBS electrode compared with postoperative CT and MRI images. Microelectrode mapping provided superior subnuclear resolution to imaging. Both intraoperative imaging and microelectrode mapping are effective tools that can be synergistically combined for optimal DBS electrode placement.

SU-F-P-42: “To Navigate, Or Not to Navigate: HDR BT in Recurrent Spine Lesions”

Purpose: We compare the accuracy of HDR catheter placement for paraspinal lesions using O-arm CBCT imaging combined with StealthStation navigation and traditional fluoroscopically guided catheter placement. Methods: CT and MRI scans were acquired pre-treatment to outline the lesions and design treatment plans (pre-plans) to meet dosimetric constrains. The pre-planned catheter trajectories were transferred into the StealthStation Navigation system prior to the surgery. The StealthStation is an infra red (IR) optical navigation system used for guidance of surgical instruments. An intraoperative CBCT scan (O-arm) was acquired with reference IR optical fiducials anchored onto the patient and registered with the preplan image study to guide surgical instruments in relation to the patients’ anatomy and to place the brachytherapy catheters along the pre-planned trajectories. The final treatment plan was generated based on a 2nd intraoperative CBCT scan reflecting achieved implant geometry. The 2nd CBCT was later registered with the initial CT scan to compare the preplanned dwell positions with actual dwell positions (catheter placements). Similar workflow was used in placement of 8 catheters (1 patient) without navigation, but under fluoroscopy guidance in an interventional radiology suite. Results: A total of 18 catheters (3 patients) were placed using navigation assisted surgery. Average displacement of 0.66 cm (STD=0.37cm) was observed between the pre-plan source positions and actual source positions in the 3 dimensional space. This translates into an average 0.38 cm positioning error in one direction including registration errors, digitization errors, and the surgeons ability to follow the planned trajectory. In comparison, average displacement of non-navigated catheters was 0.50 cm (STD=0.22cm). Conclusion: Spinal lesion HDR brachytherapy planning is a difficult task. Catheter placement has a direct impact on target coverage and dose to critical structures. While limited to a handful of patients, our experience shows navigation and fluoroscopy guided placement yield similar results.

O-arm Imaging and Naviation Systems for Transvertebral Anterior Cervical Foraminotomy

Introduction Anterior cervical discectomy and fusion (ACDF) results in excellent initial clinical results for herniated cervical disc and an osteophyte. On the other hand, the development of adjacent segment disease after ACDF is well recognized. However, most patients do not require total discectomy and vertebral fusion because most radiculopathies are caused by focal lesions of the intervertebral foramen. Especially, in patients who have unilateral radiculopathy with physiological alignment, we should avoid removal of healthy discs. Transvertebral anterior cervical foraminotomy (TVACF), nonfusion and nondiscectomy technique, can preserve intervertebral disc and reduce adjacent intervertebral degeneration compared with intervertebral fusion. Therefore, we have reported the advantages and usefulness of TVACF. However, TVACF requires skillfulness, especially for the appropriate drilling direction control for the keyhole. Recently, O-arm imaging and navigation systems were progressed. This navigation systems help to make the correct direction of the keyhole. Material and Methods We have performed TVACF under O-arm imaging and naviation systems. The patient was placed in the supine position. A lateral radiograph was used to identify the skin incision level. A 3.5cm transverse skin incision was made at half a level higher than the affected disc level. We approached the anterior surface of the vertebra from the affected side. After then, O-arm imaging and navigation systems were applied. We determined the appropriate keyhole position under the navigation. The lateral and caudal side trajectory of the tunnel was also decided under the navigation. The tunnel was ~6 mm in diameter. Results Under O-arm imaging and navigation systems, we were able to easily determine the appropriate keyhole position and the lateral and caudal side trajectory of the tunnel. Intraoperative findings and postoperative computed tomography imaging showed the accuracy of keyhole position. Conclusion Successful surgery is possible with using O-arm imaging and navigation systems. This navigation facilitate TVACF. As a result, TVACF is able to be more widely used among spinal surgeons in safe.

Economic evaluation comparing intraoperative cone beam CT-based navigation and conventional fluoroscopy for the placement of spinal pedicle screws: a patient-level data cost-effectiveness analysis

Background ContextPedicle screws are routinely used in contemporary spinal surgery. Screw misplacement may be asymptomatic but is also correlated with potential adverse events. Computer-assisted surgery (CAS) has been associated with improved screw placement accuracy rates. However, this technology has substantial acquisition and maintenance costs. Despite its increasing usage, no rigorous full economic evaluation comparing this technology to current standard of care has been reported. PurposeMedical costs are exploding in an unsustainable way. Health economic theory requires that medical equipment costs be compared with expected benefits. To answer this question for computer-assisted spinal surgery, we present an economic evaluation looking specifically at symptomatic misplaced screws leading to reoperation secondary to neurologic deficits or biomechanical concerns. Study Design/SettingThe study design was an observational case-control study from prospectively collected data of consecutive patients treated with the aid of CAS (treatment group) compared with a matched historical cohort of patients treated with conventional fluoroscopy (control group). Patient SampleThe patient sample consisted of consecutive patients treated surgically at a quaternary academic center. Outcome MeasuresThe primary effectiveness measure studied was the number of reoperations for misplaced screws within 1 year of the index surgery. Secondary outcome measures included were total adverse event rate and postoperative computed tomography usage for pedicle screw examination. MethodsA patient-level data cost-effectiveness analysis from the hospital perspective was conducted to determine the value of a navigation system coupled with intraoperative 3-D imaging (O-arm Imaging and the StealthStation S7 Navigation Systems, Medtronic, Louisville, CO, USA) in adult spinal surgery. The capital costs for both alternatives were reported as equivalent annual costs based on the annuitization of capital expenditures method using a 3% discount rate and a 7-year amortization period. Annual maintenance costs were also added. Finally, reoperation costs using a micro-costing approach were calculated for both groups. An incremental cost-effectiveness ratio was calculated and reported as cost per reoperation avoided. Based on reoperation costs in Canada and in the United States, a minimal caseload was calculated for the more expensive alternative to be cost saving. Sensitivity analyses were also conducted. ResultsA total of 5,132 pedicle screws were inserted in 502 patients during the study period: 2,682 screws in 253 patients in the treatment group and 2,450 screws in 249 patients in the control group. Overall accuracy rates were 95.2% for the treatment group and 86.9% for the control group. Within 1 year post treatment, two patients (0.8%) required a revision surgery in the treatment group compared with 15 patients (6%) in the control group. An incremental cost-effectiveness ratio of $15,961 per reoperation avoided was calculated for the CAS group. Based on a reoperation cost of $12,618, this new technology becomes cost saving for centers performing more than 254 instrumented spinal procedures per year. ConclusionsComputer-assisted spinal surgery has the potential to reduce reoperation rates and thus to have serious cost-effectiveness and policy implications. High acquisition and maintenance costs of this technology can be offset by equally high reoperation costs. Our cost-effectiveness analysis showed that for high-volume centers with a similar case complexity to the studied population, this technology is economically justified.

Comparing Radiation Dose from Conventional Fluoroscopy to Intraoperative Cone Beam CT (O-arm) during Percutaneous Lesioning Procedures of the Gasserian Ganglion.

Introduction: The use of intraoperative CT-guidance during the percutaneous treatment of trigeminal neuralgia has become increasingly popular due to the greater ease of foramen ovale cannulation and decreased procedure times. Concerns regarding radiation dose to the patient, however, remain unaddressed. We sought to compare the emitted radiation dose from fluoroscopy with intraoperative CT for these procedures.Methods: A retrospective review of percutaneous lesioning procedures for trigeminal neuralgia performed between 2010 until 2012 at our institution was conducted and radiation doses to the patient were recorded. We subsequently simulated four separate percutaneous trigeminal rhizotomies using the O-arm intraoperative CT (Medtronics, Minneapolis, MN, USA) to cannulate the foramen ovale bilaterally in two formalin-fixed cadaver heads.Results: Seventeen successful percutaneous treatments for trigeminal neuralgia were performed during the study period. Eleven procedures containing complete records were included in the final analysis. For procedures using fluoroscopy, the mean dosage was 15.2 mGys (range: 1.15 - 47.95, 95% CI 7.34 – 22.99). Radiation dosage from the O-arm imaging system was 16.55 mGy for all four cases. An unequal variance t-test did not reach statistical significance (p=0.42).Conclusions: We did not observe a significant difference in radiation dose delivered to subjects when comparing CT-guided foramen ovale cannulation relative to fluoroscopy for percutaneous lesioning of the Gasserian ganglion. Additional study is required under operational settings.

A Case-Controlled Study Evaluating the Effect of Cone Beam CT (O-Arm) Imaging and Navigation on Pedicle Screw Placement in Adult Spinal Surgery

Introduction Intraoperative CT and navigation systems (NAV) may provide an opportunity to improve precision and accuracy of pedicle screw placement, and in so doing, improve patient outcomes. Our study aimed to examine the efficacy and safety of NAV for pedicle screw placement in elective and emergent adult spinal surgery cases. We currently use this technology for surgery in all primary diagnoses of the adult spine including trauma, degenerative, deformity, revision surgery, and tumor. We sought to examine the efficacy and safety of NAV for pedicle screw placement in this broad range of surgical spinal cases. Materials and Methods All patients who underwent pedicle screw fixation with O-arm imaging and StealthStation navigation between January 2008 and December 2012 were analyzed. Patients were matched with historic case controls (non-NAV). Diagnosis, number, timing, and degree of screw malposition were recorded. Any screw with pedicle breach greater than 0 mm was recorded as misplaced. All patients had a minimum follow-up of 1 year. Quantitative statistical analysis compared screw placement between NAV and non-NAV cases. Results A total of 253 patients met the inclusion criteria by primary diagnosis in the NAV group. Diagnosis categories were not significantly different between groups (trauma 20%, oncology 12%, inflammatory arthropathy 2%, scoliotic deformity 23%, spondylolisthesis 25%, degenerative 13%, and miscellaneous other diagnoses 5%, p = 0.269). Mean number of screws placed was 11.4 in the NAV group and 10.8 in the non-NAV group ( p = 0.299) with misplaced screws in 78 patients (31%) in the NAV group and 105 (42.2%) in the non-NAV group ( p &lt; 0.009). Intraoperative screw revision rates were equivalent between groups (21 in the NAV group and 20 in the non-NAV group, p = 1); however, the number of screws revised during the same admission was significantly different (2 in the NAV group and 9 in the non-NAV group, p &lt; 0.004). Likewise, late postoperative surgical revision rates were significantly different with six patients requiring readmission for screw revision within 1 year in the non-NAV group compared with none in the NAV cohort ( p &lt; 0.008). All categories of primary diagnosis demonstrated reduction ( p &lt; 0.05) in the rate of screw malposition. Screw revision rates for individual diagnoses, however, intraoperatively or early postoperatively were not different between groups with the exception of major adult deformity ( p &lt; 0.002). Thoracic trauma pedicle screws ( p &lt; 0.005) and pedicle screws for deformity ( p &lt; 0.001) were most likely to be malpositioned. Traumatic cervical screws were most likely to require subsequent admission and screw revision. Rates of adverse events were not significantly different between groups. Reoperation for instrumentation failure was significantly different (0 cases in the NAV group and 7 in the non-NAV cohort, p &lt; 0.008). Conclusion Intraoperative 3D imaging with navigation provides an equally safe and more accurate and precise tool for pedicle screw placement than traditional techniques in adult spine surgery. Our data demonstrated a difference in the need for revision screw placement, particularly noted for deformity procedures. Considering the serious consequences of deviant screw position, the use of this technology provides a promising tool to increase patient safety and accuracy for hardware placement.

Economic Evaluation of Intraoperative Cone Beam CT-Based Navigation for the Placement of Spinal Pedicle Screws: A Patient Level Cost Effectiveness Analysis

Introduction Pedicle screws are routinely used in contemporary spinal surgery. Screw misplacement is however correlated with potential adverse events. The goal of this study is to perform an economic evaluation looking specifically at the misplaced screws leading to reoperation secondary to neurological deficits or biomechanical concerns. Material and Methods A patient-level data cost-effectiveness analysis from the hospital perspective was conducted based on a single center observational study of prospectively collected data to determine the value of a navigation system coupled with intraoperative 3D imaging (O-arm Imaging and the StealthStation S7 Navigation Systems, Medtronic, Louisville, CO) in adult spinal surgery. The data source was a consecutive series of patients treated with the aid of computer-assisted surgery (treatment group) compared with a matched historical cohort of patients treated with conventional methods (control group). The primary effectiveness measure studied was the number of reoperations for misplaced screws. Results A total of 5,132 pedicle screws were inserted in 502 patients during the study period; 2,682 screws in 253 patients in the treatment group, and 2,450 screws in 249 patients in the control group. Overall accuracy rates were 95.2% for the treatment group and 86.9% for the control group. Two patients (0.8%) required a revision surgery in the treatment group (both within the same admission) compared with 15 patients (6%) in the control group (nine within the same admission and six within 1 year during a subsequent admission). Costs of the different alternatives were assessed based on the annuitization of capital expenditures method. Using this methodology, an incremental cost effectiveness ratio of $15,961/reoperation avoided was calculated for the computer-assisted surgery group. On the basis of a reoperation cost of $12,618, this new technology becomes cost saving for centers performing more than 254 instrumented spinal procedures per year. Conclusion Computer-assisted spinal surgery has the potential to reduce reoperation rates and thus to have serious cost-effectiveness implications. High acquisition and maintenance costs of this technology can be offset by equally high reoperation costs. Our cost-effectiveness analysis showed that for high-volume centers, this technology is economically justified.

Pedicle Screw Malposition in Revision Spinal Surgery: Efficacy of Intraoperative CT-Based Navigation

Introduction The improved screw accuracy of intraoperative 3D imaging with navigation has been primarily reported in cadaveric studies and spinal deformity surgeries. Revision surgery poses unique technical challenges for pedicle screw instrumentation because of an established fusion mass, lack of reliable anatomical landmarks, and limited fixation options. The aim of this study was to examine our early experience of pedicle screw malposition rates in revision surgeries comparing O-arm and StealthStation navigated cases to the traditional freehand technique and evaluate the impact on patient outcome. Materials and Methods This ambispective study compared two matched cohorts of patients undergoing revision thoracolumbar surgery. The study group comprised 56 consecutive patients who underwent O-arm and StealthStation navigation-assisted pedicle screw instrumentation (NAV) between January 1, 2008 and December 31, 2012. The control group comprised 34 historical matched cases with surgery between January 1, 2006 and December 31, 2008, using traditional (freehand or with fluoroscopy), nonnavigated techniques (non-NAV). Cases were matched on age, gender, surgical location, number of surgical levels, and primary diagnosis. We examined the differences in screw placement and accuracy, patient outcomes, and surgery-related adverse events. Results There was a significant difference in the number of misplaced screws between the NAV and non-NAV groups (31 vs. 54, p &lt; 0.001). The average number of misplaced screws per case was 0.57 (SD = 0.92) with navigation and 1.86 (SD = 2.49) without ( p = 0.01). No difference existed in the number of screws revised intraoperatively (10 vs. 7, p = 0.54). One patient in the NAV group and two patients in the non-NAV group required early postoperative screw revision during the same admission ( p = 0.33). No screws in the NAV group required revision during subsequent admissions. No difference was observed in grade of screw malposition ( p = 0.11) or anatomical location of malposition ( p = 0.26). Anatomically, a majority of misplaced screws were located below T6 in both groups. The use of navigation resulted in a significant difference in intraoperative massive blood loss (&gt; 2L in 3 hours), 3.3% of the NAV cases compared with 7.8% of the non-NAV cases. There was no significant difference in the duration of surgery ( p = 0.11), incidence of intraoperative dural tear ( p = 1.00), wound infection ( p = 1.00), or length of stay ( p = 0.78). Conclusion This early analysis of our experience in revision surgery demonstrates an increased accuracy of pedicle screw placement utilizing O-arm imaging and StealthStation navigation systems, without an increase in OR time. Small case numbers likely explain the comparable early screw revision rates, as our experience with a larger number of degenerative cases demonstrates a statistically significant reduction in reoperation for symptomatic screw misplacement. The use of intraoperative 3D imaging and navigation in revision spine surgeries results in lower mean blood loss, and fewer cases of massive intraoperative blood loss may occur because navigation avoids the extent of dissection normally required and facilitates safe pedicle screw instrumentation while minimizing surgical exposure. Data collection and analysis is ongoing to examine diagnosis-specific incidence of screw malposition and patient outcome.