A comparison of optical and electromagnetic computer-assisted navigation systems for fluoroscopic targeting

Three-Dimensional Printed Targeting Device for Scaphoid Fracture Fixation

Background: Percutaneous guide wire insertion for scaphoid screw fixation can be challenging and often requires multiple attempts with significant radiation exposure to the surgical team. A 3-dimensional (3D) printed targeting device has the potential to reduce procedure time and intraoperative radiation exposure. Methods: Our targeting device protocol included a preprocedure computed tomography (CT) scan of a casted cadaver wrist, followed by 3D printing of a customized targeting guide. In a comparison trial, seven orthopedic surgery residents performed percutaneous scaphoid guide wire insertion on different cadaver specimens by both freehand technique and using our targeting device. Radiation exposure and procedure times were compared. All specimens underwent postprocedure CT to assess Kirschner wire (K-wire) accuracy, determined by central third placement. Pre- and postprocedure CT scans from the targeting device group were co-registered to compare planned and actual K-wire trajectories. Results: Using the freehand technique, mean fluoroscopy time was 120 seconds (standard deviation: ±53 seconds) generating 2.45 milligray of radiation. Average procedure time was 21 minutes with a mean of 6.4 (range: 3-9) insertion attempts. A single insertion attempt was made using the targeting device with an average procedure time of 30 seconds and no fluoroscopy exposure. Four K-wires were placed within the central scaphoid in both groups. Using the targeting device, average linear deviation from the planned trajectory was 2.1 mm, while the maximum linear deviation was 3.75 mm. Conclusion: When compared to freehand scaphoid guide wire insertion, our targeting device provides similar accuracy while significantly reducing intraoperative radiation exposure and procedure time.

3D-printed template and optical needle navigation in CT-guided iodine-125 permanent seed implantation

Purpose

To preliminarily verify the accuracy of navigation-assisted seed implantation by comparing pre-operative and actual differences in puncture characteristics and dosimetry in computed tomography (CT)-guided, navigation-assisted radioactive iodine-125 seed implantation, using 3D-printed templates for malignant tumors’ treatment.

Material and methods

A total of 27 tumor patients, who were treated with seed implantation under combination guidance in our hospital between December 2019 and December 2020 were enrolled in this study. Navigation needles (n = 1-3) were placed in each patient to obtain pre-operative and intra-operative puncture information, such as angle, depth, insertion point, and tip position. Moreover, dosimetry parameters in pre-operative and post-operative plans, including D₉₀, V₁₀₀, V₁₅₀, V₂₀₀, minimum peripheral dose (MPD), conformal index, external index, and homogeneity index of target area were investigated.

Results

Mean errors of the angle, depth, insertion point, and tip position were 0.5 ±0.5°, 4.0 ±2.0 mm, 1.7 ±1 mm, and 3.1 ±1.8 mm, respectively. There were no significant differences between intra-operative and pre-operative angles (p = 0.271), but there was a significant difference in the depth (p = 0.002). Errors of the angle, depth, and insertion point were larger for the pelvic/retroperitoneal area than for the head and neck/chest wall (p < 0.05). With the exception of MPD, there was no significant difference in dosimetry indices between post-operative and preoperative plans (p > 0.05).

Conclusions

Seed implantation under combination guidance showed good accuracy, and the actual intra-operative puncture information and post-operative doses were in agreement with those in the pre-operative plan, thereby demonstrating promising prospects for further development.

Design and Analysis of Customized Fixation Plate for Femoral Shaft

BACKGROUND

In the recent years, several techniques have been used to treat femur diaphyseal fracture. Among all the traditional fixation techniques, unstable fixation remains the biggest challenge for orthopedists. Researchers have recommended new approaches to deal with diaphyseal femur fracture. However, solely few had been successful in getting some better results. In the present work, a methodology comprising of design and finite-element analysis of a counter fit customized fixation plate has been suggested to provide a stable fixation.

MATERIALS AND METHODS

In the present work, reverse engineering (RE) approach has been invoked to create a 3D model of a fresh fractured femur diaphysis bone using the computed tomography (CT) scan data available in digital imaging and communications in medicine (DICOM) format. To provide stable fixation, a counter fit customized fixation plate at medial side has been designed and simulated under static physiological loading conditions for three different biocompatible materials, viz., titanium alloy (Ti6Al4V), stainless steel (SS-316L), and cobalt-chromium-molybdenum alloy (Co-Cr-Mo).

RESULTS

Static stress distribution and deformation analysis of the clinical setup have been performed for the aforementioned materials. It has been observed that the stresses and deformation developed in all the materials are quite low. It implies that customized fixation plates will provide stable fixation resulting in improved fracture union.

CONCLUSION

The proposed work will assist the medical practitioners regarding the design and analysis of customized implants. This will reduce the post surgical failures and residual pain due to non-union fractured region.

Optical and Electromagnetic Tracking Systems for Biomedical Applications: A Critical Review on Potentialities and Limitations

Optical and electromagnetic tracking systems represent the two main technologies integrated into commercially-available surgical navigators for computer-assisted image-guided surgery so far. Optical Tracking Systems (OTSs) work within the optical spectrum to track the position and orientation, i.e., pose of target surgical instruments. OTSs are characterized by high accuracy and robustness to environmental conditions. The main limitation of OTSs is the need of a direct line-of-sight between the optical markers and the camera sensor, rigidly fixed into the operating theatre. Electromagnetic Tracking Systems (EMTSs) use electromagnetic field generator to detect the pose of electromagnetic sensors. EMTSs do not require such a direct line-of-sight, however the presence of metal or ferromagnetic sources in the operating workspace can significantly affect the measurement accuracy. The aim of the proposed review is to provide a complete and detailed overview of optical and electromagnetic tracking systems, including working principles, source of error and validation protocols. Moreover, commercial and research-oriented solutions, as well as clinical applications, are described for both technologies. Finally, a critical comparative analysis of the state of the art which highlights the potentialities and the limitations of each tracking system for a medical use is provided.

Electromagnetic navigation to assist with computed tomography-guided thermal ablation of liver tumors

Purpose: To evaluate the advantages and primary technical efficacy of an electromagnetic (EM) navigation system for computed tomography (CT)-guided thermal ablation of liver tumors.Material and methods: From August 2016 to January 2018, 40 patients scheduled for CT- guided thermal ablation were prospectively enrolled and divided into two groups. Twenty patients underwent CT-guided thermal ablation with an EM navigation system (navigation group), while the other 20 patients underwent conventional CT-guided thermal ablation (control group). Data on skin punctures, instrument adjustments, puncture time to target, CT scans, CT fluoroscopy time and dose-length-product (DLP) were compared between the two groups. Any postoperative complications were recorded and the primary technical efficacy was evaluated four to six weeks after the procedure.Results: All 20 patients in the navigation group successfully underwent EM navigation. Compared to the control group, there were fewer instrument adjustments (mean 2.40 vs. 4.95; p = .003), fewer CT scans (mean 7.10 vs. 10.30; p = .006), less CT fluoroscopy time (mean 40.47 vs. 59.98 s, p = .046), and less DLP (mean 807.39 vs. 1578.67 mGy × cm; p = .001). Although not statistically significant, EM navigation resulted in fewer skin punctures (mean 1.20 vs. 1.25; p = .803) and slightly longer puncture time to target (mean 16.50 vs. 15.20 min; p = .725). No patients experienced major complications and the primary efficacy rate was 90% and 84.21% in the navigation and control groups, respectively (p = .661).Conclusions: EM navigation system optimizes the thermal ablation process and reduces radiation exposure in patients. However, further studies are warranted to determine whether an EM navigation system can improve procedure time, complication rates, and primary technical efficiacy of thermal ablation.

Anatomical axes of the proximal and distal halves of the femur in a normally aligned healthy population: implications for surgery

BACKGROUND

The anatomical axis of the femur is crucial for determining the correct alignment in corrective osteotomies of the knee, total knee arthroplasty (TKA), and retrograde and antegrade femoral intramedullary nailing (IMN). The aim of this study was to propose the concept of different anatomical axes for the proximal and distal parts of the femur; compare these axes in normally aligned subjects and also to propose the clinical application of these axes.

METHODS

In this cross-sectional study, the horizontal distances between the anatomical axis of the proximal and distal halves of the femur and the center of the intercondylar notch were measured in 100 normally aligned femurs using standard full length alignment view X-rays.

RESULTS

The average age was 34.44 ± 11.14 years. The average distance from the proximal anatomical axis to the center of the intercondylar notch was 6.68 ± 5.23 mm. The proximal anatomical axis of femur passed lateral to the center of the intercondylar notch in 12 cases (12%), medial in 84 cases (84%) and exactly central in 4 cases (4%). The average distance from the distal anatomical axis to the center of the intercondylar notch was 3.63 ± 2.09 mm. The distal anatomical axis of the femur passed medially to the center of the intercondylar notch in 82 cases (82%) and exactly central in 18 cases (18%). There was a significant difference between the anatomical axis of the proximal and distal parts of the femur in reference to the center of intercondylar notch (P value < 0.05), supporting the hypothesis that anatomical axes of the proximal and distal halves of the femur are different in the coronal plane.

CONCLUSIONS

While surgeons are aware that the anatomical axis of the distal part of the femur is different than the anatomical axis of the proximal part in patients with femoral deformities, we have shown that these axes are also different in the normally aligned healthy people due to the anatomy of the femur in coronal plane. Also the normal ranges provided here can be used as a reference for the alignment guide entry point in TKA and antegrade and retrograde intramedullary femoral nailing.

Electromagnetic Real Time Navigation in the Region of the Posterior Pelvic Ring: An Experimental In-Vitro Feasibility Study and Comparison of Image Guided Techniques

Background

Electromagnetic tracking is a relatively new technique that allows real time navigation in the absence of radiation. The aim of this study was to prove the feasibility of this technique for the treatment of posterior pelvic ring fractures and to compare the results with established image guided procedures.

Methods

Tests were performed in pelvic specimens (Sawbones^®) with standardized sacral fractures (Type Denis I or II). A gel matrix simulated the operative approach and a cover was used to disable visual control. The electromagnetic setup was performed by using a custom made carbon reference plate and a prototype stainless steel K-wire with an integrated sensor coil. Four different test series were performed: Group OCT: Optical navigation using preoperative CT-scans; group O3D: Optical navigation using intraoperative 3-D-fluoroscopy; group Fluoro: Conventional 2-D-fluoroscopy; group EMT: Electromagnetic navigation combined with a preoperative Dyna-CT. Accuracy of screw placement was analyzed by standardized postoperative CT-scan for each specimen. Operation time and intraoperative radiation exposure for the surgeon was documented. All data was analyzed using SPSS (Version 20, 76 Chicago, IL, USA). Statistical significance was defined as p< 0.05.

Results

160 iliosacral screws were placed (40 per group). EMT resulted in a significantly higher incidence of optimal screw placement (EMT: 36/40) compared to the groups Fluoro (30/40; p< 0.05) and OCT (31/40; p< 0.05). Results between EMT and O3D were comparable (O3D: 37/40; n.s.). Also, the operation time was comparable between groups EMT and O3D (EMT 7.62 min vs. O3D 7.98 min; n.s.), while the surgical time was significantly shorter compared to the Fluoro group (10.69 min; p< 0.001) and the OCT group (13.3 min; p< 0.001).

Conclusion

Electromagnetic guided iliosacral screw placement is a feasible procedure. In our experimental setup, this method was associated with improved accuracy of screw placement and shorter operation time when compared with the conventional fluoroscopy guided technique and compared to the optical navigation using preoperative CT-scans. Further studies are necessary to rule out drawbacks of this technique regarding ferromagnetic objects.

Electromagnetic tracking in medicine--a review of technology, validation, and applications

Object tracking is a key enabling technology in the context of computer-assisted medical interventions. Allowing the continuous localization of medical instruments and patient anatomy, it is a prerequisite for providing instrument guidance to subsurface anatomical structures. The only widely used technique that enables real-time tracking of small objects without line-of-sight restrictions is electromagnetic (EM) tracking. While EM tracking has been the subject of many research efforts, clinical applications have been slow to emerge. The aim of this review paper is therefore to provide insight into the future potential and limitations of EM tracking for medical use. We describe the basic working principles of EM tracking systems, list the main sources of error, and summarize the published studies on tracking accuracy, precision and robustness along with the corresponding validation protocols proposed. State-of-the-art approaches to error compensation are also reviewed in depth. Finally, an overview of the clinical applications addressed with EM tracking is given. Throughout the paper, we report not only on scientific progress, but also provide a review on commercial systems. Given the continuous debate on the applicability of EM tracking in medicine, this paper provides a timely overview of the state-of-the-art in the field.

Electromagnetic navigation reduces surgical time and radiation exposure for proximal interlocking in retrograde femoral nailing

OBJECTIVES

To compare the time required for proximal locking screw placement between a standard freehand technique and the navigated technique, and to quantify the reduction in ionizing radiation exposure.

METHODS

A fresh frozen cadaver model was used for 48 proximal interlocking screw procedures. Each procedure consisted of insertion of 2 anteroposterior locking screws. Standard fluoroscopic technique was used for 24 procedures, and an electromagnetic navigation system was used for the remaining 24 procedures. Procedure duration was recorded using an electronic timer and radiation doses were documented.

RESULTS

Mean total insertion time for both proximal interlocking screws was 405 ± 165.7 seconds with the freehand technique and 311 ± 78.3 seconds in the navigation group (P = 0.002). All procedures resulted in successful locking screw placement. Mean ionizing radiation exposure time for proximal locking was 29.5 ± 12.8 seconds.

CONCLUSIONS

Proximal locking screw insertion using the navigation technique evaluated in this work was significantly faster than the standard fluoroscopic method. The navigated technique is effective and has the potential to prevent ionizing radiation exposure.

Augmented reality-based navigation system for wrist arthroscopy: feasibility

PURPOSE

In video surgery, and more specifically in arthroscopy, one of the major problems is positioning the camera and instruments within the anatomic environment. The concept of computer-guided video surgery has already been used in ear, nose, and throat (ENT), gynecology, and even in hip arthroscopy. These systems, however, rely on optical or mechanical sensors, which turn out to be restricting and cumbersome. The aim of our study was to develop and evaluate the accuracy of a navigation system based on electromagnetic sensors in video surgery.

METHODS

We used an electromagnetic localization device (Aurora, Northern Digital Inc., Ontario, Canada) to track the movements in space of both the camera and the instruments. We have developed a dedicated application in the Python language, using the VTK library for the graphic display and the OpenCV library for camera calibration.

RESULTS

A prototype has been designed and evaluated for wrist arthroscopy. It allows display of the theoretical position of instruments onto the arthroscopic view with useful accuracy.

DISCUSSION

The augmented reality view represents valuable assistance when surgeons want to position the arthroscope or locate their instruments. It makes the maneuver more intuitive, increases comfort, saves time, and enhances concentration.

Integration of fluoroscopy-based guidance in orthopaedic trauma surgery - a prospective cohort study

INTRODUCTION

Computer-assisted guidance systems are not used frequently for musculoskeletal injuries unless there are potential advantages. We investigated a novel fluoroscopy-based image guidance system in orthopaedic trauma surgery.

MATERIALS AND METHODS

The study was a prospective, not randomised, single-centre case series at a level I trauma centre. A total of 45 patients with 46 injuries (foot 12, shoulder 10, long bones seven, hand and wrist seven, ankle seven and spine and pelvis four) were included. Different surgical procedures were examined following the basic principles of the Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF). Main outcome measurements were the number of trials for implant placement, total surgery time, usability via user questionnaire and system failure rate.

RESULTS

In all cases, the trajectory function was used, inserting a total of 56 guided implants. The system failed when used in pelvic and spinal injuries, resulting in a total failure rate of 6.5% (n=3) of all included cases. The overall usability was rated as good, scoring 84.3%.

CONCLUSION

The novel image-guidance system could be integrated into the surgical workflow and was used successfully in orthopaedic trauma surgery. Expected advantages should be explored in randomised studies.

[Electromagnetic navigation of transpedicular punctures: more precise than the standard?]

AIM

Before clinical implementation of an approved electromagnetic tracking system (CAPPA IRAD EMT) an experimental trial was performed to investigate the accuracy of the system and its safety in application for transpedicular vertebral punctures in comparison to the classical fluoroscopic method.

MATERIAL AND METHODS

A total of 110 transpedicular punctures were performed bilaterally using 11 vertebrae of 5 realistic artificial phantoms and 1 pedicle was punctured with the conventional technique using c-arm fluoroscopy and the other with the electromagnetic tracking system. As a target a radiopaque non-ferromagnetic marker was implanted bilaterally in the anterior wall of the vertebrae. For evaluation of the precision the distance from the end of the puncture to the target and the gradual deviation of the actual channel from the ideal trajectory were assessed in three-dimensional computer tomography. Calculations and statistical analysis were performed according to the Wilcoxon test by means of SPSS 16.0.1 for Windows.

RESULTS

The mean distance from the target was 6.6 mm (± 3.9 mm standard deviation SD) with electromagnetic navigation compared to 3.2 mm (± 2.8 mm SD) with fluoroscopic assistance and the mean aberration from the ideal trajectory was 18.4° (± 4.6° SD) compared to 6.5° (± 3.5° SD), respectively. The difference of accuracy was highly significant regarding both parameters (p < 0.001).

CONCLUSIONS

The minimum requirement for accuracy of transpedicular punctures could not be achieved with electromagnetic navigation. Unless proven otherwise, the lack of accuracy is attributed to unstable referencing. Despite evidence of successful employment for soft tissue punctures the system cannot currently be recommended for osseous applications of the spine.

Multimodality image fusion-guided procedures: technique, accuracy, and applications

Personalized therapies play an increasingly critical role in cancer care: Image guidance with multimodality image fusion facilitates the targeting of specific tissue for tissue characterization and plays a role in drug discovery and optimization of tailored therapies. Positron-emission tomography (PET), magnetic resonance imaging (MRI), and contrast-enhanced computed tomography (CT) may offer additional information not otherwise available to the operator during minimally invasive image-guided procedures, such as biopsy and ablation. With use of multimodality image fusion for image-guided interventions, navigation with advanced modalities does not require the physical presence of the PET, MRI, or CT imaging system. Several commercially available methods of image-fusion and device navigation are reviewed along with an explanation of common tracking hardware and software. An overview of current clinical applications for multimodality navigation is provided.

The virtual isocentric aiming device: a new mechanical targeting concept

INTRODUCTION

Minimally invasive fracture fixation can be technically demanding, especially in body regions characterised by complex bone anatomy and the presence of a significant amount of soft tissue. Hence, this procedure is associated with a high risk of implant malposition. As a consequence, radiation exposure to the patient and the surgeon increases within surgery.

AIM

The purpose of this study was to evaluate the practicability and accuracy of a newly designed virtual isocentric aiming device (VIAD) as compared to the more traditional approach of the freehand insertion of K-wires. Forty polyurethane foam blocks were prepared with a reference wire (W ( R )) and covered by sponge material to simulate soft tissue.

METHOD

For the sake of comparison, both an untrained and an experienced surgeon were selected for the study and were advised to insert a K-wire into the foam block so as to have the same axis as the W ( R ) using both of the aforementioned methods. The clinical parameters of both techniques were analysed. In addition, 3-D precision data computed using CT-scans of each sample were evaluated. Device adjustment prolonged the time required for the experienced surgeon to complete the VIAD procedure when compared to the freehand method. However, using the VIAD, the number of plane changes made to the image intensifier in addition to the number of drill trials was significantly reduced by each surgeon. Furthermore, mechanical K-wire navigation leads to a decrease in the radiation exposure time for the untrained surgeon.

RESULTS

VIAD-guided K-wires revealed a significant lower angle of deviation in relation to W ( R ). Tip-to-tip and tip-to-axis distances displayed a trend indicating reduced displacement values as well. The VIAD allows for simple wire insertion with increased precision as well as a reduction in radiation exposure, plane changes of the image intensifier and the number of drill trials compared to the freehand method.

CONCLUSION

The VIAD also satisfies the demand for a less invasive technique. Prospectively, the VIAD represents a useful and cost-effective alternative to the freehand method.