Fluoroscopy-based navigation system in spine surgery

Intraoperative Angle Measurement of Anatomical Structures: A Systematic Review

Ensuring precise angle measurement during surgical correction of orientation-related deformities is crucial for optimal postoperative outcomes, yet there is a lack of an ideal commercial solution. Current measurement sensors and instrumentation have limitations that make their use context-specific, demanding a methodical evaluation of the field. A systematic review was carried out in March 2023. Studies reporting technologies and validation methods for intraoperative angular measurement of anatomical structures were analyzed. A total of 32 studies were included, 17 focused on image-based technologies (6 fluoroscopy, 4 camera-based tracking, and 7 CT-based), while 15 explored non-image-based technologies (6 manual instruments and 9 inertial sensor-based instruments). Image-based technologies offer better accuracy and 3D capabilities but pose challenges like additional equipment, increased radiation exposure, time, and cost. Non-image-based technologies are cost-effective but may be influenced by the surgeon's perception and require careful calibration. Nevertheless, the choice of the proper technology should take into consideration the influence of the expected error in the surgery, surgery type, and radiation dose limit. This comprehensive review serves as a valuable guide for surgeons seeking precise angle measurements intraoperatively. It not only explores the performance and application of existing technologies but also aids in the future development of innovative solutions.

The machine-vision image guided surgery system reduces fluoroscopy time, ionizing radiation and intraoperative blood loss in posterior spinal fusion for scoliosis

PURPOSE

To determine if the novel 3D Machine-Vision Image Guided Surgery (MvIGS) (FLASH™) system can reduce intraoperative radiation exposure, while improving surgical outcomes when compared to 2D fluoroscopic navigation.

METHODS

Clinical and radiographic records of 128 patients (≤ 18 years of age) who underwent posterior spinal fusion (PSF), utilising either MvIGS or 2D fluoroscopy, for severe idiopathic scoliosis were retrospectively reviewed. Operative time was analysed using the cumulative sum (CUSUM) method to evaluate the learning curve for MvIGS.

RESULTS

Between 2017 and 2021, 64 patients underwent PSF using pedicle screws with 2D fluoroscopy and another 64 with the MvIGS. Age, gender, BMI, and scoliosis aetiology were comparable between the two groups. The CUSUM method estimated that the MvIGS learning curve with respect to operative time was 9 cases. This curve consisted of 2 phases: Phase 1 comprises the first 9 cases and Phase 2 the remaining 55 cases. Compared to 2D fluoroscopy, MvIGS reduced intraoperative fluoroscopy time, radiation exposure, estimated blood loss and length of stay by 53%, 62% 44%, and 21% respectively. Scoliosis curve correction was 4% higher in the MvIGS group, without any increase in operative time.

CONCLUSION

MvIGS for screw insertion in PSF contributed to a significant reduction in intraoperative radiation exposure and fluoroscopy time, as well as blood loss and length of stay. The real-time feedback and ability to visualize the pedicle in 3D with MvIGS enabled greater curve correction without increasing the operative time.

Technological Advances in Spine Surgery: Navigation, Robotics, and Augmented Reality

Accurate screw placement is critical to avoid vascular or neurologic complications during spine surgery and to maximize fixation for fusion and deformity correction. Computer-assisted navigation, robotic-guided spine surgery, and augmented reality surgical navigation are currently available technologies that have been developed to improve screw placement accuracy. The advent of multiple generations of new technologies within the past 3 decades has presented surgeons with a diverse array of choices when it comes to pedicle screw placement. Considerations for patient safety and optimal outcomes must be paramount when selecting a technology.

Virtual and Augmented Reality in Spine Surgery: A Systematic Review

BACKGROUND

Augmented reality (AR) and virtual reality (VR) implementation in spinal surgery has expanded rapidly over the past decade. This systematic review summarizes the use of AR/VR technology in surgical education, preoperative planning, and intraoperative guidance.

METHODS

A search query for AR/VR technology in spine surgery was conducted through PubMed, Embase, and Scopus. After exclusions, 48 studies were included. Included studies were then grouped into relevant subsections. Categorization into subsections yielded 12 surgical training studies, 5 preoperative planning, 24 intraoperative usage, and 10 radiation exposure.

RESULTS

VR-assisted training significantly reduced penetration rates or increased accuracy rates compared to lecture-based groups in 5 studies. Preoperative VR planning significantly influenced surgical recommendations and reduced radiation exposure, operating time, and estimated blood loss. For 3 patient studies, AR-assisted pedicle screw placement accuracy ranged from 95.77% to 100% using the Gertzbein grading scale. Head-mounted display was the most common interface used intraoperatively followed by AR microscope and projector. AR/VR also had applications in tumor resection, vertebroplasty, bone biopsy, and rod bending. Four studies reported significantly reduced radiation exposure in AR group compared to fluoroscopy group.

CONCLUSIONS

AR/VR technologies have the potential to usher in a paradigm shift in spine surgery. However, the current evidence indicates there is still a need for 1) defined quality and technical requirements for AR/VR devices, 2) more intraoperative studies that explore usage outside of pedicle screw placement, and 3) technological advancements to overcome registration errors via the development of an automatic registration method.

3D Reconstruction of Wrist Bones from C-Arm Fluoroscopy Using Planar Markers

In orthopedic surgeries, such as osteotomy and osteosynthesis, an intraoperative 3D reconstruction of the bone would enable surgeons to quickly assess the fracture reduction procedure with preoperative planning. Scanners equipped with such functionality are often more expensive than a conventional C-arm fluoroscopy device. Moreover, a C-arm fluoroscopy device is commonly available in many orthopedic facilities. Based on the widespread use of such equipment, this paper proposes a method to reconstruct the 3D structure of bone with a conventional C-arm fluoroscopy device. We focus on wrist bones as the target of reconstruction in this research as this will facilitate a flexible imaging scheme. Planar markers are attached to the target object and are tracked in the fluoroscopic image for C-arm pose estimation. The initial calibration of the device is conducted using a checkerboard pattern. In general, reconstruction algorithms are sensitive to geometric calibration errors. To assess the practicality of the method for reconstruction, a simulation study demonstrating the effect of checkerboard thickness and spherical marker size on reconstruction quality was conducted.

Towards markerless surgical tool and hand pose estimation

Purpose: 

Tracking of tools and surgical activity is becoming more and more important in the context of computer assisted surgery. In this work, we present a data generation framework, dataset and baseline methods to facilitate further research in the direction of markerless hand and instrument pose estimation in realistic surgical scenarios.

Methods: 

We developed a rendering pipeline to create inexpensive and realistic synthetic data for model pretraining. Subsequently, we propose a pipeline to capture and label real data with hand and object pose ground truth in an experimental setup to gather high-quality real data. We furthermore present three state-of-the-art RGB-based pose estimation baselines.

Results: 

We evaluate three baseline models on the proposed datasets. The best performing baseline achieves an average tool 3D vertex error of 16.7 mm on synthetic data as well as 13.8 mm on real data which is comparable to the state-of-the art in RGB-based hand/object pose estimation.

Conclusion: 

To the best of our knowledge, we propose the first synthetic and real data generation pipelines to generate hand and object pose labels for open surgery. We present three baseline models for RGB based object and object/hand pose estimation based on RGB frames. Our realistic synthetic data generation pipeline may contribute to overcome the data bottleneck in the surgical domain and can easily be transferred to other medical applications.

Supplementary Information

The online version supplementary material available at 10.1007/s11548-021-02369-2.

Current state of navigation in spine surgery

The use of navigation has become more prevalent in spine surgery. The multitude of available platforms, as well as increased availability of navigation systems, have led to increased use worldwide. Specific subsets of spine surgeons have incorporated this new technology in their practices, including minimally invasive spine (MIS) spine surgeons, neurosurgeons, and high-volume surgeons. Improved accuracy with the use of navigation has been demonstrated and its use has proven to be a safe alternative to fluoroscopic guided procedures. Navigation use allows the limitation of radiation exposure to the surgeon during common spine procedures, which over the course of a surgeon's lifetime may offer significant health benefits. Navigation has also been beneficial in tumor resection and MIS surgery, where traditional anatomic landmarks are missing or in the case of MIS not visible. As cost effectiveness improves, the use of navigation is likely to continue to expand. Navigation will also continue to expand with further innovation such as coupling the use of navigation with robotics and improving tools to enhance the end user experience.

O-arm navigation versus C-arm guidance for pedicle screw placement in spine surgery: a systematic review and meta-analysis

BACKGROUND

O-arm and C-arm are commonly used in spine surgery to guide pedicle screw placement. However, concerning the accuracy and efficiency of them, no systematical review and meta-analyses are available to help surgeons make comparisons.

PURPOSES

This study aims to investigate the accuracy and efficiency of O-arm-navigated versus C-arm-guided pedicle screw placement in thoracic and lumbar spine surgery. It would help surgeons choose the optimal technique for pedicle screw placement.

PATIENTS AND METHODS

A systematic review and meta-analyses were performed after searching the PubMed, Embase, and Cochrane databases to identify all studies that assessed the accuracy and efficiency of navigation coupled with O-arm and conventional C-arm fluoroscopy.

RESULTS

Eight studies were finally recruited in this systematic review, all of which reported pedicle screw placement outcomes related to accuracy or efficiency in both C-arm and O-arm groups. Five studies showed higher screw insertion accuracy in the O-arm group, while one study showed no significant difference. And the pooled results also indicated that the incidence of screw misplacement in the C-arm groups is higher. Moreover, the pooled results from five studies indicated no significant difference in insertion time between C-arm and O-arm.

CONCLUSIONS

Navigation coupled with O-arm imaging displayed a lower efficiency outcome in pedicle screw placement compared to conventional C-arm fluoroscopy. However, in terms of accuracy, O-arm navigation had significant advantages in accuracy over conventional C-arm fluoroscopy.

Does Three-Dimensional Printed Patient-Specific Templates Add Benefit in Revision Surgeries for Complex Pediatric Kyphoscoliosis Deformity with Sublaminar Wires in Situ? A Clinical Study

STUDY DESIGN

Case-control study.

PURPOSE

To evaluate the accuracy of three-dimensional (3D) printed patient-specific templates (PSTs) for placement of pedicle screws (PAs) in patients undergoing revision surgeries for complex kyphoscoliosis deformity with sublaminar wires in situ.

OVERVIEW OF LITERATURE

Revision kyphoscoliosis correction surgery in pediatric patients is a challenging task for the treating surgeon. In patients with sublaminar wires in situ, the native anatomical landmarks are obscured, thus making the freehand screw placement technique a highly specialized task. Hence, the concept of using PSTs for insertion of PAs in such surgeries is always intriguing and attractive.

METHODS

Five consecutive patients undergoing revision deformity correction with sublaminar wires in situ were included in this study. Patients were divided in two groups based on the technique of PA insertion. A total of 91 PAs were inserted using either a freehand technique (group A) or 3D printed templates (group B) (34 vs. 57). The placement of PAs was classified according to a postoperative computed tomography scan using Neo's classification. Perforation beyond class 2 (>2 mm) was termed as a misplaced screw. The average time required for the insertion of screws was also noted.

RESULTS

Mean age, surgical time, and blood loss were recorded. The change in mean Cobb's angle in both groups was also recorded. The difference in rates of misplaced screws was noted in group A and group B (36.21% vs. 2.56%); however, the mean number of misplaced PAs per patient in group A and group B was statistically insignificant (6.5±3.54 vs. 4.67±1.53, p =0.4641). The mean time required to insert a single PA was also statistically insignificant (120±28.28 vs. 90±30 seconds, p =0.3456).

CONCLUSIONS

Although 3D printed PSTs help to avoid the misplacement of PAs in revision deformity correction surgeries with sublaminar wires in situ, the mean number of misplaced screws per patient using this technique was found to be statistically insignificant when compared with the freehand technique in this study.

Influence of multi-angle input of intraoperative fluoroscopic images on the spatial positioning accuracy of the C-arm calibration-based algorithm of a CAOS system

Intraoperative fluoroscopic images, as one of the most important input data for computer-assisted orthopedic surgery (CAOS) systems, have a significant influence on the positioning accuracy of CAOS system. In this study, we proposed to use multi-angle intraoperative fluoroscopy images as input based on real clinical scenario, and the aim was to analyze the positioning accuracy and the error propagation rules with multi-angle input images compared with traditional two input images. In the experiment, the positioning accuracy of the C-arm calibration-based algorithm was studied, respectively, using two, three, four, five, and six intraoperative fluoroscopic images as input data. Moreover, the error propagation rules of the positioning error were analyzed by the Monte Carlo method. The experiment result showed that increasing the number of multi-angle input fluoroscopic images could reduce the positioning error of CAOS system, which has dropped from 1.01 to 0.61 mm. The Monte Carlo simulation analysis showed that for random input errors subject to normal distribution (μ = 0, σ = 1), the image positioning error dropped from 0.29 to 0.23 mm, and the staff gauge positioning error dropped from 1.36 to 1.19 mm, while the tracking device positioning error dropped from 3.41 to 2.13 mm. In addition, the results showed that image positioning error and staff gauge positioning error were all nonlinear error for the whole system, but tracker device positioning error was a strictly linear error. In conclusion, using multi-angle fluoroscopy images was helpful for clinic, which could improve the positioning accuracy of the CAOS system by nearly 30%. Graphical abstract The experiment process and Monte Carlo analysis of spatial positioning accuracy (A: Setup for the experiment; B: The process of Monte Carlo analysis; C: Results).

Evaluation of surgeon and patient radiation exposure by imaging technology in patients undergoing thoracolumbar fusion: systematic review of the literature

BACKGROUND CONTEXT

Minimally invasive spine techniques are becoming increasingly popular owing to their ability to reduce operative morbidity and recovery times. The downside to these new procedures is their need for intraoperative radiation guidance.

PURPOSE

To establish which technologies provide the lowest radiation exposure to both patient and surgeon.

STUDY DESIGN/SETTING

Systematic review OUTCOME MEASURES: Average intraoperative radiation exposure (in mSv per screw placed) to surgeon and patient. Average fluoroscopy time per screw placed.

METHODS

We reviewed the available English medical literature to identify all articles reporting patient and/or surgeon radiation exposure in patients undergoing image-guided thoracolumbar instrumentation. Quantitative meta-analysis was performed for studies providing radiation exposure or fluoroscopy use per screw placed to determine which navigation modality was associated with the lowest intraoperative radiation exposure. Values on meta-analysis were reported as mean ± standard deviation.

RESULTS

We identified 4956 unique articles, of which 85 met inclusion/exclusion criteria. Forty-one articles were included in the meta-analysis. Patient radiation exposure per screw placed for each modality was: conventional fluoroscopy without navigation (0.26±0.38 mSv), conventional fluoroscopy with pre-operative CT-based navigation (0.027±0.010 mSv), intraoperative CT-based navigation (1.20±0.91 mSv), and robot-assisted instrumentation (0.04±0.30 mSv). Values for fluoroscopy used per screw were: conventional fluoroscopy without navigation (11.1±9.0 seconds), conventional fluoroscopy with navigation (7.20±3.93 s), 3D fluoroscopy (16.2±9.6 s), intraoperative CT-based navigation (19.96±17.09 s), and robot-assistance (20.07±17.22 s). Surgeon dose per screw: conventional fluoroscopy without navigation (6.0±7.9 × 10^-3 mSv), conventional fluoroscopy with navigation (1.8±2.5 × 10^-3 mSv), 3D Fluoroscopy (0.3±1.9 × 10^-3 mSv), intraoperative CT-based navigation (0±0 mSv), and robot-assisted instrumentation (2.0±4.0 × 10^-3 mSv).

CONCLUSION

All image guidance modalities are associated with surgeon radiation exposures well below current safety limits. Intraoperative CT-based (iCT) navigation produces the lowest radiation exposure to surgeon albeit at the cost of increased radiation exposure to the patient relative to conventional fluoroscopy-based methods.

Learning curve analysis of 3D-fluoroscopy image-guided pedicle screw insertions in lumbar single-level fusion procedures

INTRODUCTION

The implementation of 3D-navigation in the operating theater is reported to be complex, time consuming, and radiation intense. This prospective single-center cohort study was performed to objectify these assumptions by determining navigation-related learning curves in lumbar single-level posterior fusion procedures using 3D-fluoroscopy for real-time image-guided pedicle screw (PS) insertions.

MATERIALS AND METHODS

From August 2011 through July 2016, a total of 320 navigated PSs were inserted during 80 lumbar single-level posterior fusion procedures by a single surgeon without any prior experience in image-guided surgery. PS misplacements, navigation-related pre- and intraoperative time demand, and procedural 3D-radiation dose (dose-length-product, DLP) were prospectively recorded and congregated in 16 subgroups of five consecutive procedures to evaluate improving PS insertion accuracy, decreasing navigation-related time demand, and reduction of 3D-radiation dose.

RESULTS

After PS insertion and intraoperative O-arm control scanning, 11 PS modifications were performed sporadically without showing "learning curve dependencies" (PS insertion accuracies in subgroups 96.6 ± 6.3%). Average navigation-related pre-surgical time from patient positioning on the operating table to skin incision decreased from 61 ± 6 min (subgroup 1) to 28 ± 2 min (subgroup 16, p < 0.00001). Average 3D-radiation dose per surgery declined from 919 ± 225 mGycm (subgroup 1) to 66 ± 4 mGycm (subgroup 16, p < 0.0001).

CONCLUSIONS

In newly inaugurated O-arm based image-guidance, lumbar PS insertions can be performed at constantly high accuracy, even without prior experience in navigated techniques. Navigation-related time demand decreases considerably due to accelerating workflow preceding skin incision. Procedural 3D-radiation dose is reducible to a fraction (13.2%) of a lumbar diagnostic non-contrast-enhanced computed tomography scan's radiation dose.

Radiation exposure for the surgical team in a hybrid-operating room

Hybrid-operating rooms enable the surgeon to acquire intraoperative high-resolution 2- and 3D images and use them for navigation. The radiation dose of the operating personal and the patient remains the major concern. In 9 months, 109 pelvic and spine cases were performed using a hybrid operating room. Radiation dose of the surgeon and the assisting nurse was recorded using real-time dosimeters. Lower radiation doses for the main surgeon in navigated dorsal instrumentations of the thoracic spine were recorded. Standing between the C-arm during screw placement increased the radiation dose sixfold. Lumbar dorsal instrumentation showed a similar radiation dose compared to the previous studies in traditional operating room settings. The use of a hybrid-operating room for dorsal spine instrumentation showed no increase in radiation dose compared to traditional settings. Intraoperative navigation can help to reduce the radiation dosage for the operating personnel.

Time Demand and Radiation Dose in 3D-Fluoroscopy-based Navigation-assisted 3D-Fluoroscopy-controlled Pedicle Screw Instrumentations

STUDY DESIGN

Prospective single-center cohort study to record additional time requirements and radiation dose in navigation-assisted O-arm-controlled pedicle screw (PS) instrumentations.

OBJECTIVE

The aim of this study was to evaluate amount of extra-time and radiation dose for navigation-assisted PS instrumentations of the thoracolumbosacral spine using O-arm 3D-real-time-navigation (O3DN) compared to non-navigated spinal procedures (NNSPs) with a single C-arm and postoperative computed tomography (CT) scan for controlling PS positions.

SUMMARY OF BACKGROUND DATA

3D-navigation is reported to enhance PS insertion accuracy. But time-consuming navigational steps and considerable additional radiation doses seem to limit this modern technique's attraction. A detailed analysis of additional time demand and extra-radiation dose in 3D-navigated spine surgery is not provided in literature, yet.

METHODS

From February 2011 through July 2015, 306 consecutive posterior instrumentations were performed in vertebral levels T10-S1 using O3DN for PS insertion. The duration of procedure-specific navigational steps of the overall collective (I) and the last cohort of 50 consecutive O3DN-surgeries (II) was compared to the average duration of analogous surgical steps in 100 consecutive NNSP using a single C-arm. 3D-radiation dose (dose-length-product, DLP) of navigational and postinstrumentation O-arm scans in group I and II was compared to the average DLP of 100 diagnostic lumbar CT scans.

RESULTS

The average presurgical time from patient positioning on the operating table to skin incision was 46.2 ± 10.1 minutes (O3DN, I) and 40.6 ± 9.8 minutes (O3DN, II) versus 30.6 ± 8.3 minutes (NNSP) (P < 0.001, each). Intraoperative interruptions for scanning and data processing took 3.0 ± 0.6 minutes. DLPs averaged 865.1 ± 360.8 mGycm (O3DN, I) and 562.1 ± 352.6 mGycm (O3DN, II) compared to 575.5 ± 316.5 mGycm in diagnostic lumbar CT scans (P < 0.001 (I), P ≈ 0.81 [II]).

CONCLUSION

After procedural experience, navigated surgeries can be performed with an additional time demand of 13.0 minutes compared to NNSP, and with a total DLP below that of a diagnostic lumbar CT scan (P ≈ 0.81).

LEVEL OF EVIDENCE

4.

Accuracy of pedicle screw insertion by AIRO® intraoperative CT in complex spinal deformity assessed by a new classification based on technical complexity of screw insertion

PURPOSE

To develop a classification based on the technical complexity encountered during pedicle screw insertion and to evaluate the performance of AIRO^® CT navigation system based on this classification, in the clinical scenario of complex spinal deformity.

MATERIALS AND METHODS

31 complex spinal deformity correction surgeries were prospectively analyzed for performance of AIRO^® mobile CT-based navigation system. Pedicles were classified according to complexity of insertion into five types. Analysis was performed to estimate the accuracy of screw placement and time for screw insertion. Breach greater than 2 mm was considered for analysis.

RESULTS

452 pedicle screws were inserted (T1-T6: 116; T7-T12: 171; L1-S1: 165). The average Cobb angle was 68.3° (range 60°-104°). We had 242 grade 2 pedicles, 133 grade 3, and 77 grade 4, and 44 pedicles were unfit for pedicle screw insertion. We noted 27 pedicle screw breach (medial: 10; lateral: 16; anterior: 1). Among lateral breach (n = 16), ten screws were planned for in-out-in pedicle screw insertion. Among lateral breach (n = 16), ten screws were planned for in-out-in pedicle screw insertion. Average screw insertion time was 1.76 ± 0.89 min. After accounting for planned breach, the effective breach rate was 3.8% resulting in 96.2% accuracy for pedicle screw placement.

CONCLUSION

This classification helps compare the accuracy of screw insertion in range of conditions by considering the complexity of screw insertion. Considering the clinical scenario of complex pedicle anatomy in spinal deformity AIRO^® navigation showed an excellent accuracy rate of 96.2%.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Fluoroscopic Confirmation of Sacral Pedicle Screw Placement Utilizing Pelvic Inlet and Outlet Technique: Technical Note

Minimally invasive surgical techniques may decrease length of stay, operative duration and blood loss, and postoperative pain. Numerous technical challenges and concerns surround the placement of percutaneous pedicle screws at the lumbosacral level. Maximization of screw triangulation, bicortical purchase, and rostral bias toward the sacral promontory has been shown repeatedly to stabilize lumbosacral segment instrumentation and maximize pullout strength. Because of the unique anatomy, conventional anteroposterior (AP) and lateral radiographic views are relatively less reliable at determining screw depth and penetration of the sacral cortex. Percutaneous sacral pedicle fixation using AP and lateral 2-dimensional fluoroscopy is complicated by the variable contour of the sacral alae and promontory. The pelvic inlet view is ideal for visualization of the ventral screw extent and is obtained by directing 45-degree cephalad and 0-degree mediolateral, with adjustments aligning the patient's pelvic brim. The modified pelvic outlet view is obtained with the trajectory axis being directed 45-degree caudal from the AP plane. This aligns the pubic symphysis with the second sacral vertebrae providing visualization of the superior boundary of the S1-bony neural foramen and any inferior wall pedicle breaches. The authors describe this reliable fluoroscopic technique and their clinical experience with percutaneous S1-screw placement.

COMPARISON OF EXPOSURE TO RADIATION DURING PERCUTANEOUS TRANSPEDICULAR PROCEDURES, USING THREE FLUOROSCOPIC TECHNIQUES

ABSTRACT Objective: To compare radiation exposure to the surgeon, patient and radiation technician during percutaneous access of the vertebral pedicle, using three different fluoroscopic imaging set up. Methods: Percutaneous access in pedicle T9-L5 of nine adult male cadavers using three different fluoroscopic set ups: standard C-arm, C-arm with L-arm, and the biplanar technique. The radiation dose exposure of the surgeon, radiation technician, and cadaver were measured using dosimeter in each procedure and in real time. Results: The radiation dose absorbed by the surgeon was higher when using the standard C-arm fluoroscopic technique than when using the C-arm with L-arm or the biplanar technique. Conclusions: The use of the C-arm with L-arm, or the biplanar fluoroscopic technique, for percutaneous access to the vertebral pedicle, reduces the radiation exposure of the surgeon compared to the standard C-arm fluoroscopic technique.

Improved Accuracy of Minimally Invasive Transpedicular Screw Placement in the Lumbar Spine With 3-Dimensional Stereotactic Image Guidance: A Comparative Meta-Analysis

STUDY DESIGN

This study compares the accuracy rates of lumbar percutaneous pedicle screw placement (PPSP) using either 2-dimensional (2-D) fluoroscopic guidance or 3-dimensional (3-D) stereotactic navigation in the setting of minimally invasive spine surgery (MISS). This represents the largest single-operator study of its kind and first comprehensive review of 3-D stereotactic navigation in the setting of MISS.

OBJECTIVE

To examine differences in accuracy of lumbar pedicle screw placement using 2-D fluoroscopic navigation and 3-D stereotaxis in the setting of MISS.

SUMMARY OF BACKGROUND DATA

Surgeons increasingly rely upon advanced image guidance systems to guide minimally invasive PPSP. Three-dimensional stereotactic navigation with intraoperative computed tomography offers well-documented benefit in open surgical approaches. However, the utility of 3-D stereotaxis in the setting of MISS remains incompletely explored by few studies with limited patient numbers.

MATERIALS AND METHODS

A total of 599 consecutive patients underwent minimally invasive lumbar PPSP aided by 3-D stereotactic navigation. Postoperative imaging and medical records were analyzed for patient demographics, incidence and degree of pedicle breach, and other surgical complications. A total of 2132 screw were reviewed and compared with a meta-analysis created from published data regarding the placement of 4248 fluoroscopically navigated pedicle screws in the setting of MISS.

RESULTS

In the 3-D navigation group, a total of 7 pedicle breaches occurred in 6 patients, corresponding to a per-person breach rate of 1.15% (6/518) and a per-screw breach rate of 0.33% (7/2132). Meta-analysis comprised of data from 10 independent studies showed overall breach risk of 13.1% when 2-D fluoroscopic navigation was utilized in MISS. This translates to a 99% decrease in odds of breach in the 3-D navigation technique versus the traditional 2-D-guided technique, with an odds ratio of 0.01, (95% confidence interval, 0.01-0.03), P<0.001.

CONCLUSIONS

Three-dimensional stereotactic navigation based upon intraoperative computed tomography imaging offers markedly improved accuracy of percutaneous lumbar pedicle screw placement when used in the setting of MISS.

Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation

BACKGROUND CONTEXT

Imaging modalities used to visualize spinal anatomy intraoperatively include X-ray studies, fluoroscopy, and computed tomography (CT). All of these emit ionizing radiation.

PURPOSE

Radiation emitted to the patient and the surgical team when performing surgeries using intraoperative CT-based spine navigation was compared.

STUDY DESIGN/SETTING

This is a retrospective cohort case-control study.

PATIENT SAMPLE

Seventy-three patients underwent CT-navigated spinal instrumentation and 73 matched controls underwent spinal instrumentation with conventional fluoroscopy.

OUTCOME MEASURES

Effective doses of radiation to the patient when the surgical team was inside and outside of the room were analyzed. The number of postoperative imaging investigations between navigated and non-navigated cases was compared.

METHODS

Intraoperative X-ray imaging, fluoroscopy, and CT dosages were recorded and standardized to effective doses. The number of postoperative imaging investigations was compared with the matched cohort of surgical cases. A literature review identified historical radiation exposure values for fluoroscopic-guided spinal instrumentation.

RESULTS

The 73 navigated operations involved an average of 5.44 levels of instrumentation. Thoracic and lumbar instrumentations had higher radiation emission from all modalities (CT, X-ray imaging, and fluoroscopy) compared with cervical cases (6.93 millisievert [mSv] vs. 2.34 mSv). Major deformity and degenerative cases involved more radiation emission than trauma or oncology cases (7.05 mSv vs. 4.20 mSv). On average, the total radiation dose to the patient was 8.7 times more than the radiation emitted when the surgical team was inside the operating room. Total radiation exposure to the patient was 2.77 times the values reported in the literature for thoracolumbar instrumentations performed without navigation. In comparison, the radiation emitted to the patient when the surgical team was inside the operating room was 2.50 lower than non-navigated thoracolumbar instrumentations. The average total radiation exposure to the patient was 5.69 mSv, a value less than a single routine lumbar CT scan (7.5 mSv). The average radiation exposure to the patient in the present study was approximately one quarter the recommended annual occupational radiation exposure. Navigation did not reduce the number of postoperative X-rays or CT scans obtained.

CONCLUSIONS

Intraoperative CT navigation increases the radiation exposure to the patient and reduces the radiation exposure to the surgeon when compared with values reported in the literature. Intraoperative CT navigation improves the accuracy of spine instrumentation with acceptable patient radiation exposure and reduced surgical team exposure. Surgeons should be aware of the implications of radiation exposure to both the patient and the surgical team when using intraoperative CT navigation.

Percutaneous “K-wireless” pedicle screw fixation technique: an evaluation of the initial experience of 100 screws with assessment of accuracy, radiation exposure, and procedure time

OBJECT

Percutaneous pedicle screws are used to provide rigid internal fixation in minimally invasive spinal procedures and generally require the use of Kirchner wires (or K-wires) as a guide for screw insertion. K-wires can bend, break, advance, or pull out during the steps of pedicle preparation and screw insertion. This can lead to increased fluoroscopic and surgical times and potentially cause neurological, vascular, or visceral injury. The authors present their experience with a novel “K-wireless” percutaneous pedicle screw system that eliminates the inherent risks of K-wire use.

METHODS

A total of 100 screws were placed in 28 patients using the K-wireless percutaneous screw system. Postoperative dedicated spinal CT scans were performed in 25 patients to assess the accuracy of screw placement. Screw placement was graded A through D by 2 independent radiologists: A = within pedicle, B = breach < 2 mm, C = breach of 2–4 mm, and D = breach > 4 mm. Screw insertion and fluoroscopy times were also recorded in each case. Clinical complications associated with screw insertion were documented.

RESULTS

A total of 100 K-wireless percutaneous pedicle screws were placed into the lumbosacral spine in 28 patients. Postoperative CT was performed in 25 patients, thus the placement of only 90 screws was assessed. Eighty-seven screws were placed within the pedicle confines (Grade A), and 3 violated the pedicle (2 Grade B [1 lateral, 1 medial] and 1 Grade D [medial]) for an overall accuracy rate of 96.7%. One patient required reoperation for screw repositioning due to a postoperative L-5 radiculopathy secondary to a Grade D medial breach at L-5. This patient experienced improvement of the radiculopathy after reoperation. Average screw insertion and fluoroscopy times were 6.92 minutes and 22.7 seconds per screw, respectively.

CONCLUSIONS

The results of this study demonstrate that the placement of K-wireless percutaneous pedicle screws is technically feasible and can be performed accurately and safely with short procedure and fluoroscopy times.

Computer-aided surgery does not increase the accuracy of dorsal pedicle screw placement in the thoracic and lumbar spine: a retrospective analysis of 2,003 pedicle screws in a level I trauma center

Study Design A retrospective analysis of a prospective database. Objective Meta-analyses suggest that computer-assisted systems can increase the accuracy of pedicle screw placement for dorsal spinal fusion procedures. The results of further meta-analyses report that in the thoracic spine, both the methods have comparable placement accuracy. These studies are limited due to an abundance of screw classification systems. The aim of this study was to assess the placement accuracy and potentially influencing factors of three-dimensionally navigated versus conventionally inserted pedicle screws. Methods This was a retrospective analysis of a prospective database at a level I trauma center of pedicle screw placement (computer-navigated versus traditionally placed) for dorsal spinal stabilizations. The cases spanned a 5.5-year study period (January 1, 2005, to June 30, 2010). The perforations of the pedicle were differentiated in three grades based on the postoperative computed tomography. Results The overall placement accuracy was 86% in the conventional group versus 79% in the computer-navigated group (grade 0). The computer-navigated procedures were superior in the lumbar spine and the conventional procedures were superior in the thoracic spine, but both failed to be of statistical significance. The level of experience of the performing surgeon and the patient's body mass index did not influence the placement accuracy. The only significant influence was the spinal segment: the higher the spinal level where the fusion was performed, the more likely the screw was displaced. Conclusions The computer-navigated and conventional methods are both safe procedures to place transpedicular screws at the traumatized thoracic and lumbar spine. At the moment, three-dimensionally based navigation does not significantly increase the placement accuracy.

The evolution of image-guided lumbosacral spine surgery

Techniques and approaches of spinal fusion have considerably evolved since their first description in the early 1900s. The incorporation of pedicle screw constructs into lumbosacral spine surgery is among the most significant advances in the field, offering immediate stability and decreased rates of pseudarthrosis compared to previously described methods. However, early studies describing pedicle screw fixation and numerous studies thereafter have demonstrated clinically significant sequelae of inaccurate surgical fusion hardware placement. A number of image guidance systems have been developed to reduce morbidity from hardware malposition in increasingly complex spine surgeries. Advanced image guidance systems such as intraoperative stereotaxis improve the accuracy of pedicle screw placement using a variety of surgical approaches, however their clinical indications and clinical impact remain debated. Beginning with intraoperative fluoroscopy, this article describes the evolution of image guided lumbosacral spinal fusion, emphasizing two-dimensional (2D) and three-dimensional (3D) navigational methods.

[Intraoperative virtual implant planning for volar plate osteosynthesis of distal radius fractures]

BACKGROUND

Digital planning of implants is in most cases conducted prior to surgery. The virtual implant planning system (VIPS) is an application developed for mobile C-arms, which assists the virtual planning of screws close to the joint line during surgery for treatment of distal radius fractures with volar plate osteosynthesis. The aim of this prospective randomized study was to acquire initial clinical experiences and to compare the VIPS method with the conventional technique.

METHOD

The study included 10 patients for primary testing and 30 patients with distal radius fractures of types A3, C1 and C2, divided in 2 groups. In the VIPS group, after placement of the plate and fracture reduction, a virtual 3D model of the plate was matched with the image of the plate from the fluoroscopic acquisition. Next, the length and position of the screws close to the joint line were planned on the virtual plate. The control group was treated with the same implant in the conventional way. Data were collected regarding screw replacement, fluoroscopy and operating room (OR) times.

RESULTS

The VIPS group included six A3, one C1 and eight C2 fractures, while the control group consisted of six A3 and nine C2 fractures. Three screws were replaced in the VIPS group and two in the control group (p = 0.24). The mean intraoperative fluoroscopy time of the VIPS group amounted to 2.58 ± 1.38 min, whereas it was 2.12 ± 0.73 min in the control group (p = 0.26). The mean OR time in the VIPS group was 53.3 ± 34.5 minutes and 42.3 ± 8.8 min (p = 0.23) in the control group.

CONCLUSION

The VIPS enables a precise positioning of screws close to joint line in the treatment of distal radius fractures; however, for routine use, further development of the system is necessary.

Robotic assisted surgeries for the treatment of spine tumors

Background

Surgery plays an important role in the treatment of patients with metastatic or primary spine tumors. In recent years, various new techniques, such as robotic assisted spine surgery have been developed which has shown some promising results by improving the accuracy of spinal instrumentation and reducing potential complications. The purpose of this study was to evaluate our early experience using robotic guidance in the treatment of spinal tumors.

Methods

Data were collected from medical records for each surgery in which the robotic system was used to assist with biopsy, pedicle screw placement and/or vertebral augmentation in the treatment of spinal tumors. Patient's age, gender, diagnosis and surgical procedure were documented. The surgical time, estimated blood loss, peri-operative and post-operative complications were obtained. The visual analog scale (VAS) for back pain and leg pain were also recorded.

Results

A total of 9 consecutive patients (7 female, 2 male) were included in this study, beginning with the first case experience. The mean age of the patients was 60 years (range 47-69). All patients presented with thoracic or lumbar vertebral collapse and/or myelopathy. Robotic assisted posterior instrumentation was successfully performed in all patients. Robotic assisted vertebral augmentation was performed in 4 patients. The average number of levels instrumented was 5. The average surgery time (skin to skin) was 4 hours and 24 minutes and the mean blood loss was 319 ml. There were no complications perioperatively or through the latest follow-up. Seven of the 9 patients reported improved back pain and/or leg pain at the latest follow-up and the data were not available in two patients.

Conclusions

The published complication rates of spinal tumor surgeries range between 5.3% and 19%. With robotic assistance, the surgical complication rate appears improved over the historical figures. Our study shows that the robotic system was safe and performed as desired in the treatment of metastatic and primary spine tumors. These results support that further evaluation in a larger series of patients.

Safety and efficacy of pedicle screw placement using intraoperative computed tomography: consecutive series of 1148 pedicle screws

Object

A number of imaging techniques have been introduced to minimize the risk of pedicle screw placement. Intraoperative CT has been recently introduced to assist in spinal instrumentation. The aim of this study was to study the effectiveness of intraoperative CT in enhancing the safety and accuracy of pedicle screw placement.

Methods

The authors included all cases from December 2009 through July 2012 in which intraoperative CT scanning was used to confirm pedicle screw placement.

Results

A total of 203 patients met the inclusion criteria. Of 1148 screws, 103 screws (8.97%) were revised intraoperatively in 72 patients (35.5%): 14 (18.42%) were revised in the cervical spine (C-2 or C-7), 25 (7.25%) in the thoracic spine, and 64 (8.80%) in the lumbar spine. Compared with screws in the thoracic and lumbar regions, pedicle screws placed in the cervical region were statistically more likely to be revised (p = 0.0061). Two patients (0.99%) required reoperations due to undetected misplacement of pedicle screws.

Conclusions

The authors describe one of the first North American experiences using intraoperative CT scanning to confirm the placement of pedicle screws. Compared with a similar cohort of patients from their institution who had pedicle screws inserted via the free-hand technique with postoperative CT, the authors found that the intraoperative CT lowers the threshold for pedicle screw revision, resulting in a statistically higher rate of screw revision in the thoracic and lumbar spine (p < 0.0001). During their 2.5-year experience with the intraoperative CT, the authors did not find a reduction in rates of reoperation for misplaced pedicle screws.

Techniques and accuracy of thoracolumbar pedicle screw placement

Pedicle screw instrumentation has been used to stabilize the thoracolumbar spine for several decades. Although pedicle screws were originally placed via a free-hand technique, there has been a movement in favor of pedicle screw placement with the aid of imaging. Such assistive techniques include fluoroscopy guidance and stereotactic navigation. Imaging has the benefit of increased visualization of a pedicle’s trajectory, but can result in increased morbidity associated with radiation exposure, increased time expenditure, and possible workflow interruption. Many institutions have reported high accuracies with each of these three core techniques. However, due to differing definitions of accuracy and varying radiographic analyses, it is extremely difficult to compare studies side-by-side to determine which techniques are superior. From the literature, it can be concluded that pedicles of vertebrae within the mid-thoracic spine and vertebrae that have altered morphology due to scoliosis or other deformities are the most difficult to cannulate. Thus, spine surgeons would benefit the most from using assistive technologies in these circumstances. All other pedicles in the thoracolumbar spine should theoretically be cannulated with ease via a free-hand technique, given appropriate training and experience. Despite these global recommendations, appropriate techniques must be chosen at the surgeon’s discretion. Such determinations should be based on the surgeon’s experience and the specific pathology that will be treated.

Position and complications of pedicle screw insertion with or without image-navigation techniques in the thoracolumbar spine: a meta-analysis of comparative studies

Computer-navigated pedicle screw insertion is applied to the thoracic and lumbar spine to attain high insertion accuracy and a low rate of screw-related complications. However, some in vivo and in vitro studies have shown that no advantages are gained with the use of navigation techniques compared to conventional techniques. Additionally, inconsistent conclusions have been drawn in various studies due to different population characteristics and methods used to assess the accuracy of screw placement. Moreover, it is not clear whether pedicle screw insertion with navigation techniques decreases the incidence of screw-related complications. Therefore, this study was sought to perform a meta-analysis of all available prospective evidence regarding pedicle screw insertion with or without navigation techniques in human thoracic and lumbar spine. We considered in vivo comparative studies that assessed the results of pedicle screw placement with or without navigation techniques. PubMed, Ovid MEDLINE and EMBASE databases were searched. Three published randomized controlled trials (RCTs) and nine retrospective comparative studies met the inclusion criteria. These studies included a total of 732 patients in whom 4,953 screws were inserted. In conclusion, accuracy of the position of grade I, II, III and IV screws and complication rate related to pedicle screw placement were significantly increased when navigation techniques were used in comparison to conventional techniques. Future research in this area should include RCTs with well-planned methodology to limit bias and report on validated, patient-based outcome measures.

Clinical evaluation of the polymethylmethacrylate-augmented thoracic and lumbar pedicle screw fixation guided by the three-dimensional navigation for the osteoporosis patients

PURPOSE

To evaluate the safety and efficacy of three-dimensional (3D) navigation-guided polymethylmethacrylate (PMMA)-augmented thoracic and lumbar pedicle screw fixation for the osteoporotic patients.

METHODS

27 consecutive osteoporosis patients with a variety of spinal disorders who underwent 3D navigation-guided PMMA-augmented pedicle screw fixation were evaluated clinically and radiologically in the perioperative and 1-year follow-up period. The improvement of Japanese Orthopaedic Association (JOA) scores was analyzed. PMMA leakage and other complications were inspected intraoperatively and postoperatively. Screw loosening and bone fusion were evaluated radiographically during follow-up.

RESULTS

8 patients had thoracic and lumbar fractures; 18 patients had degenerative spinal disorders; one patient had revision surgery. One patient died of postoperative pneumonia. Each of the other 26 patients was followed up regularly at 3, 6, 12 and 18 months postoperatively. The mean therapeutic improvement rate is 39.6% evaluated by JOA scores. 2 patients (7.4%) had leakage into the spinal canal in front of the posterior longitudinal ligament and two patients (7.4%) had leakage into the prevertebral soft tissue inspected by the postoperative CT scans. No pedicle cortex breach and cement leakage surrounding pedicle cortex were observed. None of patients complained of dyspnoea and showed evidence of pulmonary embolism. Bone fusions were found in 20 patients (bony fusion rate 76.9%) at the 12-month follow-up and no screw loosening occurs.

CONCLUSION

The results show favorable outcome using 3D navigation-guided PMMA-augmented thoracic and lumbar pedicle screw fixation for the osteoporosis patients both clinically and radiologically.

The accuracy of pedicle screw placement using intraoperative image guidance systems

OBJECT

Several retrospective studies have demonstrated higher accuracy rates and increased safety for navigated pedicle screw placement than for free-hand techniques; however, the accuracy differences between navigation systems has not been extensively studied. In some instances, 3D fluoroscopic navigation methods have been reported to not be more accurate than 2D navigation methods for pedicle screw placement. The authors of this study endeavored to identify if 3D fluoroscopic navigation methods resulted in a higher placement accuracy of pedicle screws.

METHODS

A systematic analysis was conducted to examine pedicle screw insertion accuracy based on the use of 2D, 3D, and conventional fluoroscopic image guidance systems. A PubMed and MEDLINE database search was conducted to review the published literature that focused on the accuracy of pedicle screw placement using intraoperative, real-time fluoroscopic image guidance in spine fusion surgeries. The pedicle screw accuracy rates were segregated according to spinal level because each spinal region has individual anatomical and morphological variations. Descriptive statistics were used to compare the pedicle screw insertion accuracy rate differences among the navigation methods.

RESULTS

A total of 30 studies were included in the analysis. The data were abstracted and analyzed for the following groups: 12 data sets that used conventional fluoroscopy, 8 data sets that used 2D fluoroscopic navigation, and 20 data sets that used 3D fluoroscopic navigation. These studies included 1973 patients in whom 9310 pedicle screws were inserted. With conventional fluoroscopy, 2532 of 3719 screws were inserted accurately (68.1% accuracy); with 2D fluoroscopic navigation, 1031 of 1223 screws were inserted accurately (84.3% accuracy); and with 3D fluoroscopic navigation, 4170 of 4368 screws were inserted accurately (95.5% accuracy). The accuracy rates when 3D was compared with 2D fluoroscopic navigation were also consistently higher throughout all individual spinal levels.

CONCLUSIONS

Three-dimensional fluoroscopic image guidance systems demonstrated a significantly higher pedicle screw placement accuracy than conventional fluoroscopy or 2D fluoroscopic image guidance methods.

An evaluation of three-dimensional image-guided technologies in percutaneous pelvic and acetabular lag screw placement

BACKGROUND

Percutaneous stabilization using three-dimensional (3D) navigation system is a promising treatment for pelvic and acetabular fractures. However, there are still some controversies regarding the use of 3D navigation to treat pelvic and acetabular fractures. The purpose of this study was to compare the Iso-C(3D) fluoroscopic navigation, standard fluoroscopy, and two-dimensional (2D) fluoroscopic navigation in placing percutaneous lag screws in pelvic specimens to better understand the merits of 3D navigation techniques.

METHODS

Fifty-four instrumentation procedures were performed in this study using six cadaveric pelvic specimens. Three groups were designated for different procedures and tests: group I, standard fluoroscopy; group II, 2D fluoroscopic navigation; and group III, Iso-C(3D) fluoroscopic navigation. Nine screws were placed in each pelvis, including four screws placed bilaterally through the ilium into S1 and S2 vertebrae, four screws placed bilaterally through anterior and posterior columns of acetabulum, and one screw placed through the pubic symphysis. 3D fluoroscopic techniques were evaluated to determine the accuracy of screw position, instrumentation time, and fluoroscopic time. The data were statistically analyzed using SPSS 13.0.

RESULTS

The malposition rate was 38.89%, 22.22%, and 0% in standard fluoroscopy, 2D fluoroscopic navigation, and Iso-C(3D) fluoroscopic navigation groups, respectively. There was no significant difference between standard fluoroscopy and 2D fluoroscopic navigation. Compared with Iso-C(3D) fluoroscopic navigation, there were significant differences (analysis of variance [ANOVA], P < 0.05). The mean instrumentation operating time using Iso-C(3D) fluoroscopic navigation technique was 15.4 ± 4.5 min. There were significant differences compared with standard fluoroscopy (31.5 ± 6.2 min) and 2D fluoroscopic navigation (26.3 ± 7.5 min; ANOVA, post hoc Scheffe, P < 0.01). The mean fluoroscopic time of Iso-C(3D) fluoroscopic navigation was 66 ± 4.8 min. Compared with standard fluoroscopy (132.8 ± 7.3 min) and 2D fluoroscopic navigation (47.7 ± 5.6 min), there were significant differences (ANOVA, post hoc least significant difference, P < 0.01).

CONCLUSIONS

In the present study, we compared Iso-C(3D) fluoroscopic navigation, 2D fluoroscopic navigation, and standard fluoroscopy. Iso-C(3D) fluoroscopic navigation showed a higher accuracy rate in positioning and a shorter instrumentation operating time. The fluoroscopic time was longer in Iso-C(3D) fluoroscopic navigation than that in standard fluoroscopy, indicating that radiation exposure can be moderately reduced in Iso-C(3D) fluoroscopic navigation operation, although the fluoroscopic time was the shortest in 2D fluoroscopic navigation.

Preoperative analysis of the stability of fit of a patient-specific surgical guide

Although the use of patient-specific surgical guides has gained popularity over the past decade, little research has been done to examine in an objective and qualitative way the fit of such instruments. In this study, we have developed a model to predict the stability of a guide designed to fit on a supporting bone surface, thereby providing feedback on the translational and rotational stability of the device. The method was validated by comparing different guide designs with respect to their stability on the contact surface and comparing these results to those measured with a set of experiments. This validation experiment indicates that our stability model can be used to predict the stability of the fit of a surgical guide during the preoperative design process.

Robotic-assisted pedicle screw placement: lessons learned from the first 102 patients

INTRODUCTION

Surgeons' interest in image and/or robotic guidance for spinal implant placement is increasing. This technology is continually improving and may be particularly useful in patients with challenging anatomy. Only through careful clinical evaluation can its successful applications, limitations, and areas for improvement be defined. This study evaluates the outcomes of robotic-assisted screw placement in a consecutive series of 102 patients.

METHODS

Data were recorded from technical notes and operative records created immediately following each surgery case, in which the robotic system was used to guide pedicle screw placement. All cases were performed at the same hospital by a single surgeon. The majority of patients had spinal deformity and/or previous spine surgery. Each planned screw placement was classified as: (1) successful/accurately placed screw using robotic guidance; (2) screw malpositioned using robot; (3) use of robot aborted and screw placed manually; (4) planned screw not placed as screw deemed non essential for construct stability. Data from each case were reviewed by two independent researchers to indentify the diagnosis, number of attempted robotic guided screw placements and the outcome of the attempted placement as well as complications or reasons for non-placement.

RESULTS

Robotic-guided screw placement was successfully used in 95 out of 102 patients. In those 95 patients, 949 screws (87.5 % of 1,085 planned screws) were successfully implanted. Eleven screws (1.0 %) placed using the robotic system were misplaced (all presumably due to "skiving" of the drill bit or trocar off the side of the facet). Robotic guidance was aborted and 110 screws (10.1 %) were manually placed, generally due to poor registration and/or technical trajectory issues. Fifteen screws (1.4 %) were not placed after intraoperative determination that the screw was not essential for construct stability. The robot was not used as planned in seven patients, one due to severe deformity, one due to very high body mass index, one due to extremely poor bone quality, one due to registration difficulty caused by previously placed loosened hardware, one due to difficulty with platform mounting and two due to device technical issues.

CONCLUSION

Of the 960 screws that were implanted using the robot, 949 (98.9 %) were successfully and accurately implanted and 11 (1.1 %) were malpositioned, despite the fact that the majority of patients had significant spinal deformities and/or previous spine surgeries. "Tool skiving" was thought to be the inciting issue with the misplaced screws. Intraoperative anteroposterior and oblique fluoroscopic imaging for registration is critical and was the limiting issue in four of the seven aborted cases.

Accuracy and Safety in Pedicle Screw Placement in the Thoracic and Lumbar Spines : Comparison Study between Conventional C-Arm Fluoroscopy and Navigation Coupled with O-Arm® Guided Methods

Objective

The authors performed a retrospective study to assess the accuracy and clinical benefits of a navigation coupled with O-arm® system guided method in the thoracic and lumbar spines by comparing with a C-arm fluoroscopy-guided method.

Methods

Under the navigation guidance, 106 pedicle screws inserted from T7 to S1 in 24 patients, and using the fluoroscopy guidance, 204 pedicle screws from T5 to S1 in 45 patients. The position of screws within the pedicle was classified into four groups, from grade 0 (no violation cortex) to 3 (more than 4 mm violation). The location of violated pedicle cortex was also assessed. Intra-operative parameters including time required for preparation of screwing procedure, times for screwing and the number of X-ray shot were assessed in each group.

Results

Grade 0 was observed in 186 (91.2%) screws of the fluoroscopy-guided group, and 99 (93.4%) of the navigation-guided group. Mean time required for inserting a screw was 3.8 minutes in the fluoroscopy-guided group, and 4.5 minutes in the navigation-guided group. Mean time required for preparation of screw placement was 4 minutes in the fluoroscopy-guided group, and 19 minutes in the navigation-guided group. The fluoroscopy-guided group required mean 8.9 times of X-ray shot for each screw placement.

Conclusion

The screw placement under the navigation-guidance coupled with O-arm® system appears to be more accurate and safer than that under the fluoroscopy guidance, although the preparation and screwing time for the navigation-guided surgery is longer than that for the fluoroscopy-guided surgery.

Pedicle screw navigation: a systematic review and meta-analysis of perforation risk for computer-navigated versus freehand insertion

Object

In this paper the authors' goal was to compare the accuracy of computer-navigated pedicle screw insertion with nonnavigated techniques in the published literature.

Methods

The authors performed a systematic literature review using the National Center for Biotechnology Information Database (PubMed/MEDLINE) using the Medical Subject Headings (MeSH) terms “Neuronavigation,” “Therapy, computer assisted,” and “Stereotaxic techniques,” and the text word “pedicle.” Included in the meta-analysis were randomized control trials or patient cohort series, all of which compared computer-navigated spine surgery (CNSS) and nonassisted pedicle screw insertions. The primary end point was pedicle perforation, while the secondary end points were operative time, blood loss, and complications.

Results

Twenty studies were included for analysis; of which there were 18 cohort studies and 2 randomized controlled trials published between 2000 and 2011. Foreign-language papers were translated. The total number of screws included was 8539 (4814 navigated and 3725 nonnavigated). The most common indications for surgery were degenerative disease, spinal deformity, myelopathy, tumor, and trauma. Navigational methods were primarily based on CT imaging. All regions of the spine were represented. The relative risk for pedicle screw perforation was determined to be 0.39 (p < 0.001), favoring navigation. The overall pedicle screw perforation risk for navigation was 6%, while the overall pedicle screw perforation risk was 15% for conventional insertion. No related neurological complications were reported with navigated insertion (4814 screws total); there were 3 neurological complications in the nonnavigated group (3725 screws total). Furthermore, the meta-analysis did not reveal a significant difference in total operative time and estimated blood loss when comparing the 2 modalities.

Conclusions

There is a significantly lower risk of pedicle perforation for navigated screw insertion compared with nonnavigated insertion for all spinal regions.

An on-board surgical tracking and video augmentation system for C-arm image guidance

PURPOSE

Conventional tracker configurations for surgical navigation carry a variety of limitations, including limited geometric accuracy, line-of-sight obstruction, and mismatch of the view angle with the surgeon's-eye view. This paper presents the development and characterization of a novel tracker configuration (referred to as "Tracker-on-C") intended to address such limitations by incorporating the tracker directly on the gantry of a mobile C-arm for fluoroscopy and cone-beam CT (CBCT).

METHODS

A video-based tracker (MicronTracker, Claron Technology Inc., Toronto, ON, Canada) was mounted on the gantry of a prototype mobile isocentric C-arm next to the flat-panel detector. To maintain registration within a dynamically moving reference frame (due to rotation of the C-arm), a reference marker consisting of 6 faces (referred to as a "hex-face marker") was developed to give visibility across the full range of C-arm rotation. Three primary functionalities were investigated: surgical tracking, generation of digitally reconstructed radiographs (DRRs) from the perspective of a tracked tool or the current C-arm angle, and augmentation of the tracker video scene with image, DRR, and planning data. Target registration error (TRE) was measured in comparison with the same tracker implemented in a conventional in-room configuration. Graphics processing unit (GPU)-accelerated DRRs were generated in real time as an assistant to C-arm positioning (i.e., positioning the C-arm such that target anatomy is in the field-of-view (FOV)), radiographic search (i.e., a virtual X-ray projection preview of target anatomy without X-ray exposure), and localization (i.e., visualizing the location of the surgical target or planning data). Video augmentation included superimposing tracker data, the X-ray FOV, DRRs, planning data, preoperative images, and/or intraoperative CBCT onto the video scene. Geometric accuracy was quantitatively evaluated in each case, and qualitative assessment of clinical feasibility was analyzed by an experienced and fellowship-trained orthopedic spine surgeon within a clinically realistic surgical setup of the Tracker-on-C.

RESULTS

The Tracker-on-C configuration demonstrated improved TRE (0.87 ± 0.25) mm in comparison with a conventional in-room tracker setup (1.92 ± 0.71) mm (p < 0.0001) attributed primarily to improved depth resolution of the stereoscopic camera placed closer to the surgical field. The hex-face reference marker maintained registration across the 180° C-arm orbit (TRE = 0.70 ± 0.32 mm). DRRs generated from the perspective of the C-arm X-ray detector demonstrated sub- mm accuracy (0.37 ± 0.20 mm) in correspondence with the real X-ray image. Planning data and DRRs overlaid on the video scene exhibited accuracy of (0.59 ± 0.38) pixels and (0.66 ± 0.36) pixels, respectively. Preclinical assessment suggested potential utility of the Tracker-on-C in a spectrum of interventions, including improved line of sight, an assistant to C-arm positioning, and faster target localization, while reducing X-ray exposure time.

CONCLUSIONS

The proposed tracker configuration demonstrated sub- mm TRE from the dynamic reference frame of a rotational C-arm through the use of the multi-face reference marker. Real-time DRRs and video augmentation from a natural perspective over the operating table assisted C-arm setup, simplified radiographic search and localization, and reduced fluoroscopy time. Incorporation of the proposed tracker configuration with C-arm CBCT guidance has the potential to simplify intraoperative registration, improve geometric accuracy, enhance visualization, and reduce radiation exposure.

Accuracy of pedicle screw placement: a systematic review of prospective in vivo studies comparing free hand, fluoroscopy guidance and navigation techniques

INTRODUCTION

With the advances and improvement of computer-assisted surgery devices, computer-guided pedicle screws insertion has been applied to the lumbar, thoracic and cervical spine. The purpose of the present study was to perform a systematic review of all available prospective evidence regarding pedicle screw insertion techniques in the thoracic and lumbar human spine.

MATERIALS AND METHODS

We considered all prospective in vivo clinical studies in the English literature that assessed the results of different pedicle screw placement techniques (free-hand technique, fluoroscopy guided, computed tomography (CT)-based navigation, fluoro-based navigation). MEDLINE, OVID, and Springer databases were used for the literature search covering the period from January 1950 until May 2010.

RESULTS

26 prospective clinical studies were eventually included in the analysis. These studies included in total 1,105 patients in which 6,617 screws were inserted. In the studies using free-hand technique, the percentage of the screws fully contained in the pedicle ranged from 69 to 94%, with the aid of fluoroscopy from 28 to 85%, using CT navigation from 89 to 100% and using fluoroscopy-based navigation from 81 to 92%. The screws positioned with free-hand technique tended to perforate the cortex medially, whereas the screws placed with CT navigation guidance seemed to perforate more often laterally.

CONCLUSIONS

In conclusion, navigation does indeed exhibit higher accuracy and increased safety in pedicle screw placement than free-hand technique and use of fluoroscopy.