Spinal Navigation and Imaging: History, Trends, and Future

Prediction of the upright articulated spine shape in the operating room using conditioned neural kernel fields

Anterior vertebral tethering (AVT) is a non-invasive spine surgery technique, treating severe spine deformations and preserving lower back mobility. However, patient positioning and surgical strategies greatly influences postoperative results. Predicting the upright geometry from pediatric spines is needed to optimize patient positioning in the operating room (OR) and improve surgical outcomes, but remains a complex task due to immature bone properties. We propose a framework used in the OR predicting the upright spine geometry at the first visit following surgery in idiopathic scoliosis patients. The approach first creates a 3D model of the spine while the patient is on the operating table. For this, multiview Transformers that combine images from different viewpoints are used to generate the intraoperative pose. The postoperative upright shape is then predicted on-the-fly using implicit neural fields, which are trained from geometries at different time points and conditioned with surgical parameters. A Signed Distance Function for shape constellations is used to handle the variability in spine appearance, capturing a disentangled latent domain of the articulation vectors, with separate encoding vectors representing both articulation and shape parameters. A regularization criterion based on a pre-trained group-wise trajectory of spine transformations generates complete spine models. A training set of 652 patients with 3D models was used to train the model, tested on a distinct cohort of 83 surgical patients. The framework based on neural kernels predicted upright 3D geometries with a mean 3D error of 1.3±0.5mm in landmarks points, and IoU of 95.9% in vertebral shapes when compared to actual postop models, falling within the acceptable margins of error below 2 mm.

A Novel Marking Technique for Accurate Minimal Invasive Approaches in Spine Tumor Surgeries With Activated Carbon Marking

BACKGROUND AND OBJECTIVES

To describe a novel, practical, reproducible, and effective preoperative marking technique for accurate localization of the spinal level in a series of patients with tumor lesions.

METHODS

We retrospectively analyzed patients undergoing minimally invasive (MIS) surgery for spine tumors from 2016 to 2021, in which this marking technique was used. Twenty-one patients, with tumor lesions involving difficult radioscopic visualization (cervicothoracic junction or upper dorsal spine, C6-T8), were included. Tumor lesion level was previously determined with enhanced MRI in all cases. Twenty-four to forty-eight hours before surgery, computed tomography image-guided carbon marking was performed by administration of aqueous suspension of carbon with a 21-gauge needle placed resembling the MIS approach planned trajectory. During surgery, activated carbon marking was followed until reaching the final target on the bone. Next, sequential dilators and an MIS retractor were placed. Then, bone resection and tumor exeresis were performed according to the case.

RESULTS

Average age was 60.6 years (26-76 years). Fifteen (71%) patients were women. In most cases (76%), tumor pathology involved intradural lesions (meningiomas and schwannomas). In all cases, the marking described allowed to accurately guide the MIS approach to tumor site. Neither intraoperative fluoroscopy nor approach enlargement was required in any procedure. Postoperative complications were reported in only 4 patients, none related with the marking.

CONCLUSION

Computed tomography image-guided activated carbon marking allows to accurately lead MIS approaches in a practical, reproducible, and effective way in cases of tumors localized in regions of the spine of difficult radioscopic visualization.

Comparison of different imaging devices and navigation systems for cervical pedicle screw placement: an experimental study on screw accuracy, screw placement time and radiation dose

Cervical pedicle screws (CPS) provide biomechanically superior fixation compared to other techniques but are technically more demanding. Navigated CPS placement has been increasingly reported as a safe and accurate technique, yet there are few studies comparing different combinations of imaging and navigation systems under comparable conditions. With this study, we aimed to compare different imaging and navigation systems for CPS placement in terms of accuracy, screw placement time and applied radiation dose. For this experimental study, navigated CPS placement was performed at levels C2 to C7 in 24 identical radiopaque artificial spine models by two surgeons with different levels of experience using three different combinations of intraoperative 3D imaging devices and navigation systems. Accuracy, time and radiation dose were compared between the groups. In total, 288 screws were placed. Accuracy was > 98% in all groups with no significant differences between groups or between surgeons (P = 0.30 and P = 0.31, respectively), but the inexperienced surgeon required significantly more time (P < 0.001). Radiation dose was significantly higher with iCT compared to CBCT (P < 0.0001). Under experimental conditions, accuracy rates of > 98% were achieved for navigated CPS placement regardless of the imaging modality or navigation system used. Radiation doses were significantly lower for CBCT compared to iCT guidance.

Navigation and Robotic Single-Position Prone LLIF: First Cases in Brazil

OBJECTIVE

has been rapid technological advancement in navigation-guided minimally invasive surgery over the past two decades, making these advancements an invaluable aid for surgeons by essentially providing real-time virtual reconstruction of patient anatomy. The objectives of these navigation- and robot-guided procedures are to reduce the likelihood of neural and vascular injury, minimize hospitalization time, decrease bleeding and postoperative pain, shorten healing time, and lower infection rates.

METHODS

A unicentric, retrospective cohort study was conducted to evaluate the preoperative and postoperative clinical and radiographic outcomes of the first Latin American patients diagnosed with lumbar degenerative disease who underwent lumbar interbody fusion at the L4-L5 level via prone-position lateral lumbar interbody fusion-single position prone access.

RESULTS

A total of 80 patients (40 assisted by fluoroscopy, 40 assisted by robotics) with 320 percutaneous pedicle screws were evaluated. The primary outcomes analyzed and compared were radiation exposure per screw (seconds), skin-to-skin operative time (minutes), and recovery time (days). Secondary outcomes included lumbar pain intensity (visual analog scale), reported functional disability (Oswestry Disability Index), and any potential complications. All secondary outcomes were collected at the postoperative time.

CONCLUSION

Comparing minimally invasive spine interventions with free-hand instrumentation and robotic instrumentation, a statistically significant difference was identified in radiation exposure per screw and surgical time. The literature on Cirq Robotic is limited; however, minimally invasive spine surgery with robotic assistance appears advantageous in terms of radiation exposure and surgical time.

The Impact of Navigation in Lumbar Spine Surgery: A Study of Historical Aspects, Current Techniques and Future Directions

Background/Objectives: We sought to improve accuracy while minimizing radiation hazards, improving surgical outcomes, and preventing potential complications. Despite the increasing popularity of these systems, a limited number of papers have been published addressing the historical evolution, detailing the areas of use, and discussing the advantages and disadvantages, of this increasingly popular system in lumbar spine surgery. Our objective was to offer readers a concise overview of navigation system history in lumbar spine surgeries, the techniques involved, the advantages and disadvantages, and suggestions for future enhancements to the system. Methods: A comprehensive review of the literature was conducted, focusing on the development and implementation of navigation systems in lumbar spine surgeries. Our sources include PubMed-indexed peer-reviewed journals, clinical trial data, and case studies involving technologies such as computer-assisted surgery (CAS), image-guided surgery (IGS), and robotic-assisted systems. Results: To develop more practical, effective, and accurate navigation techniques for spine surgery, consistent advancements have been made over the past four decades. This technological progress began in the late 20th century and has since encompassed image-guided surgery, intraoperative imaging, advanced navigation combined with robotic assistance, and artificial intelligence. These technological advancements have significantly improved the accuracy of implant placement, reducing the risk of misplacement and related complications. Navigation has also been found to be particularly useful in tumor resection and minimally invasive surgery (MIS), where conventional anatomic landmarks are lacking or, in the case of MIS, not visible. Additionally, these innovations have led to shorter operative times, decreased radiation exposure for patients and surgical teams, and lower rates of reoperation. As navigation technology continues to evolve, future innovations are anticipated to further enhance the capabilities and accessibility of these systems, ultimately leading to improved patient outcomes in lumbar spine surgery. Conclusions: The initial limited utilization of navigation system in spine surgery has further expanded to encompass almost all fields of lumbar spine surgeries. As the cost-effectiveness and number of trained surgeons improve, a wider use of the system will be ensured so that the navigation system will be an indispensable tool in lumbar spine surgery. However, continued research and development, along with training programs for surgeons, are essential to fully realize the potential of these technologies in clinical practice.

Task-based image quality assessment of an intraoperative CBCT for spine surgery compared with conventional CT

PURPOSE

To analyze the image quality of a novel, state-of-the art platform for CBCT image-guided spine surgery, focusing particularly on the dose-effectiveness compared with conventional CT (the gold standard for postoperative assessment).

METHODS

The ClarifEye platform (Philips Healthcare) with integrated augmented-reality surgical navigation, has been compared with a GE Revolution CT (GE Healthcare). The 3D spatial resolution (TTF) and noise (NPS) were evaluated considering relevant feature contrasts (200-900 HU) and background noise for differently sized patients (200-300 mm water-equivalent diameter). These measures were used to determine the noise equivalent quanta (NEQ) and observer model detectability.

RESULTS

The CBCT system exhibited a linear response with 50% TTF at 5.7 cycles/cm (10% TTF at 9.2 cycles/cm), and the axial noise power peaking at about 3.6 cycles/cm (average frequency of 4.1 cycles/cm). The noise magnitude and texture differed markedly compared to iteratively reconstructed CT images (GE ASiR-V). The CBCT system had 26% lower detectability for a high-frequency task (related to edge detection) compared with CT images reconstructed using the Bone kernel combined with ASiR-V 50%. Likewise, it had 18% lower detectability for low- and mid-frequency tasks compared with CT images reconstructed using the Standard kernel. This difference translates to 50%-80% higher CBCT imaging doses required to match the CT image quality.

CONCLUSIONS

The ClarifEye platform demonstrates intraoperative CBCT-imaging capabilities that under certain circumstances are comparable with conventional CT. However, due to limited dose-effectiveness, a trade-off between timeliness and radiation exposure must be considered if end-of-procedure CBCT is to replace postoperative CT.

Clinical Application and Curative Effect Analysis of Postural Awareness Surgical Tool Assisted Nail Placement in Adolescent Idiopathic Scoliosis

OBJECTIVE

The pedicle screw technique has been widely used in adolescent idiopathic scoliosis orthopedic surgery, but misplacement of screws may damage important structures such as blood vessels and nerves around the pedicle, resulting in serious consequences. Therefore, our research team has independently developed a surgical tool to assist in the placement of pedicle screws. This study aims to investigate the safety and accuracy of postural awareness tool assisted nail placement in orthopedic surgery for adolescent idiopathic scoliosis.

METHOD

A retrospective analysis was performed on 24 adolescent patients with idiopathic scoliosis admitted to our hospital from July 2019 to July 2022, including 10 males and 14 females, with an average age of 14.88 ± 2.36 years (10-19 years). The mean follow-up was 15.67 ± 2.20 months (12-20 months). We divided the patients into postural awareness group (n = 12) and C-arm group (n = 12) according to whether the postural awareness surgical tool was used during the operation. All patients were treated with posterior spinal orthopedic surgery. The postural awareness group was assisted by pedicle screw placement with a postural awareness surgical tool, while the C-arm group was given a pedicle screw placement with freehand technique. The operative time, intraoperative blood loss, intraoperative fluoroscopy times, nail placement related complications, nail placement accuracy, and scoliosis correction rate were recorded and compared between the two groups.

RESULTS

The operative time, intraoperative blood loss and fluoroscopy times in the postural awareness group were significantly lower than those in the C-arm group, with statistical significance (p < 0.05). The postural awareness group implanted 163 screws with an accuracy rate of 91.41%, while the C-arm group implanted 159 screws with an accuracy rate of 83.02%. The accuracy rate of screw placement in the postural awareness group was higher than that in the C-arm group, with a statistically significant difference (p = 0.024). According to the imaging of the patients, there was no significant difference between the Cobb Angle of the main bend measured at three time points before surgery, 1 week after surgery and the last follow-up between the two groups. Similarly, there was no significant difference in the rate of lateral curvature correction between the two groups.

CONCLUSION

The application of postural awareness surgical tool in posterior orthopedic surgery for adolescent idiopathic scoliosis can improve screw placement accuracy, shorten screw placement time, and make auxiliary screw placement safer and more accurate.

Top 25 Most Cited Articles on Intraoperative Computer Tomography-Guided Navigation in Spine Surgery

BACKGROUND

In recent years, the use of intraoperative computer tomography-guided (CT-guided) navigation has gained significant popularity among health care providers who perform minimally invasive spine surgery. This review aims to identify and analyze trends in the literature related to the widespread adoption of CT-guided navigation in spine surgery, emphasizing the shift from conventional fluoroscopy-based techniques to CT-guided navigation.

METHODS

Articles pertaining to this study were identified via a database review and were hierarchically organized based on the number of citations. An "advanced document search" was performed on September 28th, 2022, utilizing Boolean search operator terms. The 25 most referenced articles were combined into a primary list after sorting results in descending order based on the total number of citations.

RESULTS

The "Top 25" list for intraoperative CT-guided navigation in spine surgery cumulatively received a total of 2742 citations, with an average of 12 new citations annually. The number of citations ranged from 246 for the most cited article to 60 for the 25th most cited article. The most cited article was a paper by Siewerdsen et al., with 246 total citations, averaging 15 new citations per year.

CONCLUSIONS

Intraoperative CT-guided navigation is 1 of many technological advances that is used to increase surgical accuracy, and it has become an increasingly popular alternative to conventional fluoroscopy-based techniques. Given the increasing adoption of intraoperative CT-guided navigation in spine surgery, this review provides impactful evidence for its utility in spine surgery.

Innovations in Spine Surgery: A Narrative Review of Current Integrative Technologies

Neurosurgical technologies have become increasingly more adaptive, featuring real-time and patient-specific guidance in preoperative, intraoperative, and postoperative settings. This review offers insight into how these integrative innovations compare with conventional approaches in spine surgery, focusing on machine learning (ML), artificial intelligence, augmented reality and virtual reality, and spinal navigation systems. Data on technology applications, diagnostic and procedural accuracy, intraoperative times, radiation exposures, postoperative outcomes, and costs were extracted and compared with conventional methods to assess their advantages and limitations. Preoperatively, augmented reality and virtual reality have applications in surgical training and planning that are more immersive, case specific, and risk-free and have been shown to enhance accuracy and reduce complications. ML algorithms have demonstrated high accuracy in predicting surgical candidacy (up to 92.1%) and tailoring personalized treatments based on patient-specific variables. Intraoperatively, advantages include more accurate pedicle screw insertion (96%-99% with ML), enhanced visualization, reduced radiation exposure (49 μSv with O-arm navigation vs. 556 μSv with fluoroscopy), increased efficiency, and potential for fewer intraoperative complications compared with conventional approaches. Postoperatively, certain ML and artificial intelligence models have outperformed conventional methods in predicting all postoperative complications of >6000 patients as well as predicting variables contributing to in-hospital and 90-day mortality. However, applying these technologies comes with limitations, such as longer operative times (up to 35.6% longer) with navigation, dependency on datasets, costs, accessibility, steep learning curve, and inherent software malfunctions. As these technologies advance, continuing to assess their efficacy and limitations will be crucial to their successful integration within spine surgery.

Surgical Management of Primary Thoracic Epidural Melanoma

In this study, we reported one of the first cases where a rare robotic-assisted platform with neuronavigation technology and carbon-fiber-polyetheretherketone (CF/PEEK) screws is employed to surgically treat multilevel thoracic primary spinal epidural melanoma. A 67-year-old male presented with left upper thoracic pain. His magnetic resonance imaging (MRI) of the thoracic spine revealed a dumbbell-shaped left epidural mass at the T2-3 level. Partial resection was performed due to tumor growth into the vertebral bodies and patient discretion for minimal surgery. The patient's neurological conditions improved postoperatively, with reduced reported symptoms of pain and numbness. Postoperative imaging showed evidence of appropriate spinal stabilization. Patient underwent stereotactic body radiation therapy (SBRT), and no adverse events were reported. This case reflects one of the first examples of treating thoracic epidural melanoma with the use of robotic-assisted navigation. Further prospective studies are needed to determine the efficacy of robot-assisted navigation for patients with primary spinal malignant melanoma which may open the possibility of surgery to once presumed non-operative patients.

Our C-Arm-Free Minimally Invasive Technique for Spinal Surgery: The Thoracolumbar and Lumbar Spine-Based on Our Experiences

Background and Objectives: The implementation of intraoperative imaging in the procedures performed under the guidance of the same finds its history dating back to the early 1990s. This practice was abandoned due to many deficits and practicality. Later, fluoroscopy-dependent techniques were developed and have been used even in the present time, albeit with several disadvantages. With the recent advancement of several complex surgical techniques, which demand higher accuracy and are in conjunction with the existence of radiation exposure hazard, C-arm-free techniques were introduced. In this review study, we aim to demonstrate the various types of these techniques performed in our hospital. Materials and Methods: We have retrospectively analyzed and collected imaging data of C-arm-free, minimally invasive techniques performed in our hospital. The basic steps of the procedures are described, following with a discussion, along with the literature of findings, enlisting the merits and demerits. Results: MIS techniques of the thoracolumbar and lumbar spine that do not require the use of the C-arm can offer excellent results with high precision. However, several disadvantages may prevail in certain circumstances such as the navigation accuracy problem where in the possibility of perioperative complications comes a high morbidity rate. Conclusions: The accustomedness of performing these techniques requires a steep learning curve. The increase in accuracy and the decrease in radiation exposure in complex spinal surgery can overcome the burden hazards and can prove to be cost-effective.

The feasibility of a new self-guided pedicle tap for pedicle screw placement: an anatomical study

PURPOSE

To investigate the safety and accuracy of applying a new self-guided pedicle tap to assist pedicle screw placement.

METHODS

A new self-guided pedicle tap was developed based on the anatomical and biomechanical characteristics of the pedicle. Eight adult spine specimens, four males and four females, were selected and tapped on the left and right sides of each pair of T1-L5 segments using conventional taps (control group) and new self-guided pedicle taps (experimental group), respectively, and pedicle screws were inserted. The screw placement time of the two groups were recorded and compared using a stopwatch. The safety and accuracy of screw placement were observed by CT scanning of the spine specimens and their imaging results were graded according to the Heary grading criteria.

RESULTS

Screw placement time of the experimental group were (5. 73 ± 1. 18) min in thoracic vertebrae and (5. 09 ± 1. 31) min in lumbar vertebrae respectively. Screw placement time of the control group were respectively (6. 02 ± 1. 54) min in thoracic vertebrae and (5.51 ± 1.42) min in lumbar vertebrae. The difference between the two groups was not statistically significant (P > 0. 05). The Heary grading of pedicle screws showed 112 (82.35%) Heary grade I screws and 126 (92.65%) Heary grade I + II screws in the experimental group, while 96 (70.59%) Heary grade I screws and 112 (82.35%) Heary grade I + II screws in the control group.The difference between the two groups was statistically significant (P < 0.05).

CONCLUSION

The new self-guided pedicle tap can safely and accurately place thoracic and lumbar pedicle screws with low-cost and convenient procedure,which indicates a good clinical application value.

Sonification as a reliable alternative to conventional visual surgical navigation

Despite the undeniable advantages of image-guided surgical assistance systems in terms of accuracy, such systems have not yet fully met surgeons' needs or expectations regarding usability, time efficiency, and their integration into the surgical workflow. On the other hand, perceptual studies have shown that presenting independent but causally correlated information via multimodal feedback involving different sensory modalities can improve task performance. This article investigates an alternative method for computer-assisted surgical navigation, introduces a novel four-DOF sonification methodology for navigated pedicle screw placement, and discusses advanced solutions based on multisensory feedback. The proposed method comprises a novel four-DOF sonification solution for alignment tasks in four degrees of freedom based on frequency modulation synthesis. We compared the resulting accuracy and execution time of the proposed sonification method with visual navigation, which is currently considered the state of the art. We conducted a phantom study in which 17 surgeons executed the pedicle screw placement task in the lumbar spine, guided by either the proposed sonification-based or the traditional visual navigation method. The results demonstrated that the proposed method is as accurate as the state of the art while decreasing the surgeon's need to focus on visual navigation displays instead of the natural focus on surgical tools and targeted anatomy during task execution.

Basis for error in stereotactic and computer-assisted surgery in neurosurgical applications: literature review

Technological advancements in optoelectronic motion capture systems have allowed for the development of high-precision computer-assisted surgery (CAS) used in cranial and spinal surgical procedures. Errors generated sequentially throughout the chain of components of CAS may have cumulative effect on the accuracy of implant and instrumentation placement - potentially affecting patient outcomes. Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of CAS. Error reporting measures vary between studies. Understanding error generation, mechanisms of propagation, and how they relate to workflow can assist clinicians in error mitigation and improve accuracy during navigation in neurosurgical procedures. Diligence in planning, fiducial positioning, system registration, and intra-operative workflow have the potential to improve accuracy and decrease disparity between planned and final instrumentation and implant position. This study reviews the potential errors associated with each step in computer-assisted surgery and provides a basis for disparity in intrinsic accuracy versus achieved accuracy in the clinical operative environment.

A new technique useful for lumbosacral percutaneous pedicle screw placement without fluoroscopy or computer-aided navigation systems

BACKGROUND

Percutaneous pedicle screw (PPS) placements in the lumbosacral spine generally rely on fluoroscopy at the expense of radiation exposure. Our accumulated experience in open PS placements without fluoroscopic guidance realized a consistent shift toward PPS insertion with newly developed devices, which require neither fluoroscopy nor navigation. We wish to report our new technique and evaluations of its accuracy.

METHODS

Our equipment consisted of a pedicle targeting tool to identify and escort the cannulated awl to the correct starting point for cortical bone perforation and a cannulated awl-probe system with a guidewire to maintain the optimal position throughout the subsequent surgical steps. The surgeon could advance the blunt-tipped probe searching for the cancellous bone track using tactile feedback as experienced in open techniques. A 2-year period of transition from a free-hand (1169 screws in 286 patients) to the new PPS technique (1933 screws in 413 patients) allowed accuracy comparison between the two procedures using postoperative CT scans.

RESULTS

Compared with the open-group, the PPS-group showed a lower rate of fully contained intrapedicular PS placements at L1 through S1, as a whole (90.7% vs 85.4%), but not at L4 through S1 (89.9% vs 90.2%). Less-accurate PPS placements at upper than lower lumbar spines in part reflect intended pedicle perforations laterally as a trade-off for avoiding facet violation immediately above the most cephalad screw. The PPS-group also had a higher incidence of PS-related transient nerve root complications (0% vs 1.7%). These values for the PPS-group, however, fell within those previously reported for free-hand or fluoroscopy techniques.

CONCLUSIONS

Our new PPS technique, although useful for eliminating the potential risk of repeated radiation exposure, fell short of reaching the accuracy of the free-hand technique. Nerve integrity monitoring with PS stimulation, which we currently use, will help further improve the technical precision.

STUDY DESIGN

Original Article. The study was approved by our institutional review boad (2,019,231).

A photoacoustics-enhanced drilling probe for radiation-free pedicle screw implantation in spinal surgery

This article proposes a novel intra-operative navigation and sensing system that optimizes the functional accuracy of spinal pedicle screw implantation. It does so by incorporating radiation-free and multi-scale macroscopic 3D ultrasound (US) imaging and local tissue-awareness from in situ photoacoustic (PA) sensing at a clinically relevant mesoscopic scale. More specifically, 3D US imaging is employed for online status updates of spinal segment posture to determine the appropriate entry point and coarse drilling path once non-negligible or relative patient motion occurs between inter-vertebral segments in the intra-operative phase. Furthermore, a sophisticated sensor-enhanced drilling probe has been developed to facilitate fine-grained local navigation that integrates a PA endoscopic imaging component for in situ tissue sensing. The PA signals from a sideways direction to differentiate cancellous bone from harder cortical bone, or to indicate weakened osteoporotic bone within the vertebrae. In so doing it prevents cortical breaches, strengthens implant stability, and mitigates iatrogenic injuries of the neighboring artery and nerves. To optimize this PA-enhanced endoscopic probe design, the light absorption spectrum of cortical bone and cancellous bone are measured in vitro, and the associated PA signals are characterized. Ultimately, a pilot study is performed on an ex vivo bovine spine to validate our developed multi-scale navigation and sensing system. The experimental results demonstrate the clinical feasibility, and hence the great potential, for functionally accurate screw implantation in complex spinal stabilization interventions.

Preclinical evaluation of a prototype freehand drill video guidance system for orthopedic surgery

Purpose: Internal fixation of pelvic fractures is a challenging task requiring the placement of instrumentation within complex three-dimensional bone corridors, typically guided by fluoroscopy. We report a system for two- and three-dimensional guidance using a drill-mounted video camera and fiducial markers with evaluation in first preclinical studies. Approach: The system uses a camera affixed to a surgical drill and multimodality (optical and radio-opaque) markers for real-time trajectory visualization in fluoroscopy and/or CT. Improvements to a previously reported prototype include hardware components (mount, camera, and fiducials) and software (including a system for detecting marker perturbation) to address practical requirements necessary for translation to clinical studies. Phantom and cadaver experiments were performed to quantify the accuracy of video-fluoroscopy and video-CT registration, the ability to detect marker perturbation, and the conformance in placing guidewires along realistic pelvic trajectories. The performance was evaluated in terms of geometric accuracy and conformance within bone corridors. Results: The studies demonstrated successful guidewire delivery in a cadaver, with a median entry point error of 1.00 mm (1.56 mm IQR) and median angular error of 1.94 deg (1.23 deg IQR). Such accuracy was sufficient to guide K-wire placement through five of the six trajectories investigated with a strong level of conformance within bone corridors. The sixth case demonstrated a cortical breach due to extrema in the registration error. The system was able to detect marker perturbations and alert the user to potential registration issues. Feasible workflows were identified for orthopedic-trauma scenarios involving emergent cases (with no preoperative imaging) or cases with preoperative CT. Conclusions: A prototype system for guidewire placement was developed providing guidance that is potentially compatible with orthopedic-trauma workflow. First preclinical (cadaver) studies demonstrated accurate guidance of K-wire placement in pelvic bone corridors and the ability to automatically detect perturbations that degrade registration accuracy. The preclinical prototype demonstrated performance and utility supporting translation to clinical studies.

Minimally Invasive Spine Surgery: An Overview

Spinal surgery is undergoing a major transformation toward a minimally invasive paradigm. This shift is being driven by multiple factors, including the need to address spinal problems in an older and sicker population, as well as changes in patient preferences and reimbursement patterns. Increasingly, minimally invasive surgical techniques are being used in place of traditional open approaches due to significant advancements and implementation of intraoperative imaging and navigation technologies. However, in some patients, due to specific anatomic or pathologic factors, minimally invasive techniques are not always possible. Numerous algorithms have been described, and additional efforts are underway to better optimize patient selection for minimally invasive spinal surgery (MISS) procedures in order to achieve optimal outcomes. Numerous unique MISS approaches and techniques have been described, and several have become fundamental. Investigators are evaluating combinations of MISS techniques to further enhance the surgical workflow, patient safety, and efficiency.

Real-time vascular anatomical image navigation for laparoscopic surgery: experimental study

BACKGROUND

Recognition of the inferior mesenteric artery (IMA) during colorectal cancer surgery is crucial to avoid intraoperative hemorrhage and define the appropriate lymph node dissection line. This retrospective feasibility study aimed to develop an IMA anatomical recognition model for laparoscopic colorectal resection using deep learning, and to evaluate its recognition accuracy and real-time performance.

METHODS

A complete multi-institutional surgical video database, LapSig300 was used for this study. Intraoperative videos of 60 patients who underwent laparoscopic sigmoid colon resection or high anterior resection were randomly extracted from the database and included. Deep learning-based semantic segmentation accuracy and real-time performance of the developed IMA recognition model were evaluated using Dice similarity coefficient (DSC) and frames per second (FPS), respectively.

RESULTS

In a fivefold cross-validation conducted using 1200 annotated images for the IMA semantic segmentation task, the mean DSC value was 0.798 (± 0.0161 SD) and the maximum DSC was 0.816. The proposed deep learning model operated at a speed of over 12 FPS.

CONCLUSION

To the best of our knowledge, this is the first study to evaluate the feasibility of real-time vascular anatomical navigation during laparoscopic colorectal surgery using a deep learning-based semantic segmentation approach. This experimental study was conducted to confirm the feasibility of our model; therefore, its safety and usefulness were not verified in clinical practice. However, the proposed deep learning model demonstrated a relatively high accuracy in recognizing IMA in intraoperative images. The proposed approach has potential application in image navigation systems for unfixed soft tissues and organs during various laparoscopic surgeries.

Efficacy of Single-Position Oblique Lateral Interbody Fusion Combined With Percutaneous Pedicle Screw Fixation in Treating Degenerative Lumbar Spondylolisthesis: A Cohort Study

Objective

To investigate the surgical outcomes of single-position oblique lateral interbody fusion (OLIF) combined with percutaneous pedicle screw fixation (PPSF) in treating degenerative lumbar spondylolisthesis (DLS).

Methods

We retrospectively analyzed 85 patients with DLS who met the inclusion criteria from April 2018 to December 2020. According to the need to change their position during the operation, the patients were divided into a single-position OLIF group (27 patients) and a conventional OLIF group (58 patients). The operation time, intraoperative blood loss, hospitalization days, instrumentation accuracy and complication rates were compared between the two groups. The visual analog scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate the clinical efficacy. The surgical segment's intervertebral space height (IDH) and lumbar lordosis (LL) angle were used to evaluate the imaging effect.

Results

The hospital stay, pedicle screws placement accuracy, and complication incidence were similar between the two groups (P > 0.05). The operation time and intraoperative blood loss in the single-position OLIF group were less than those in the conventional OLIF group (P < 0.05). The postoperative VAS, ODI, IDH and LL values were significantly improved (P < 0.05), but there was no significant difference between the two groups (P > 0.05).

Conclusions

Compared with conventional OLIF, single-position OLIF combined with PPSF is also safe and effective, and it has the advantages of a shorter operation time and less intraoperative blood loss.

Percutaneous Posterior Cervical Pedicle Instrumentation (C1 to C7) With Navigation Guidance: Early Series of 27 Cases

STUDY DESIGN

This is a technique paper describing minimally invasive, navigated, percutaneous pedicle screw fixation of the cervical spine. In addition, we include a retrospective feasibility analysis of our initial experience with 27 patients undergoing this procedure.

OBJECTIVE

The purpose of this study is to describe the technique of MIS navigated percutaneous cervical pedicle screw instrumentation and to report our initial experience.

METHODS

This is a retrospective review of 27 patients undergoing MIS navigated percutaneous posterior cervical pedicle screw fixation at 2 institutions. We describe the technique and report the radiographic outcomes and all intraoperative and postoperative complications.

RESULTS

A total of 27 patients underwent MIS navigated percutaneous pedicle screw fixation. Indications included odontoid fracture, subaxial fracture dislocations and burst fracture, pathological fracture, and degenerative spondylosis. There were no nerve root or vascular injuries. There were no spinal cord injuries. Two screws required repositioning intraoperatively, and 1 patient required reoperation for symptomatic malpositioned screw.

CONCLUSIONS

MIS navigated percutaneous posterior pedicle screw fixation can be performed safely. These constructs are biomechanically superior with neurovascular complication rates comparable to traditional lateral mass screw technique. While the current indications for this technique are relatively limited, the evolution of MIS cervical decompression techniques as well as navigation and robotics will provide an expanded role for percutaneous cervical pedicle screw instrumentation.

Comparative Analysis of Optoelectronic Accuracy in the Laboratory Setting Versus Clinical Operative Environment: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The optoelectronic camera source and data interpolation process serve as the foundation for navigational integrity in robotic-assisted surgical platforms. The current systematic review serves to provide a basis for the numerical disparity observed when comparing the intrinsic accuracy of optoelectronic cameras versus accuracy in the laboratory setting and clinical operative environments.

METHODS

Review of the PubMed and Cochrane Library research databases was performed. The exhaustive literature compilation obtained was then vetted to reduce redundancies and categorized into topics of intrinsic accuracy, registration accuracy, musculoskeletal kinematic platforms, and clinical operative platforms.

RESULTS

A total of 465 references were vetted and 137 comprise the basis for the current analysis. Regardless of application, the common denominators affecting overall optoelectronic accuracy are intrinsic accuracy, registration accuracy, and application accuracy. Intrinsic accuracy equaled or was less than 0.1 mm translation and 0.1 degrees rotation per fiducial. Controlled laboratory platforms reported 0.1 to 0.5 mm translation and 0.1 to 1.0 degrees rotation per array. Accuracy in robotic-assisted spinal surgery reported 1.5 to 6.0 mm translation and 1.5 to 5.0 degrees rotation when comparing planned to final implant position.

CONCLUSIONS

Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of robotic-assisted spinal surgery. Transitioning from controlled laboratory to clinical operative environments requires an increased number of steps in the optoelectronic kinematic chain and error potential. Diligence in planning, fiducial positioning, system registration and intra-operative workflow have the potential to improve accuracy and decrease disparity between planned and final implant position.

Systematic Review: Applications of Intraoperative Ultrasound in Spinal Surgery

BACKGROUND

Due to increased practicality and decreased costs and radiation, interest has risen for intraoperative ultrasound (iUS) in spinal surgery applications; however, few studies have provided a robust overview of its use in spinal surgery. We synthesize findings of existing literature on usage of iUS in navigation, pedicle screw placement, and identification of anatomy during spinal interventions.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were utilized in this systematic review. Studies were identified through PubMed, Scopus, and Google Scholar databases using the search string. Abstracts mentioning iUS in spine applications were included. Upon full-text review, exclusion criteria were implemented, including outdated studies or those with weak topic relevance or statistical power. Upon elimination of duplicates, multi-reviewer screening for eligibility, and citation search, 44 manuscripts were analyzed.

RESULTS

Navigation using iUS is safe, effective, and economical. iUS registration accuracy and success is within clinically acceptable limits for image-guided navigation (Table 2). Pedicle screw instrumentation with iUS is precise with a favorable safety profile (Table 2). Anatomical landmarks are reliably identified with iUS, and surgeons are overwhelmingly successful in neural or vascular tissue identification with iUS modalities including standard B mode, doppler, and contrast-enhanced ultrasound (CE-US) (Table 3). iUS use in traumatic reduction of fractures properly identifies anatomical structures, intervertebral disc space, and vasculature (Table 3).

CONCLUSION

iUS eliminates radiation, decreases costs, and provides sufficient accuracy and reliability in identification of anatomical and neurovascular structures in various spinal surgery settings.

Cervical Spine Pedicle Screw Accuracy in Fluoroscopic, Navigated and Template Guided Systems-A Systematic Review

Background: Pedicle screws provide excellent fixation for a wide range of indications. However, their adoption in the cervical spine has been slower than in the thoracic and lumbar spine, which is largely due to the smaller pedicle sizes and the proximity to the neurovascular structures in the neck. In recent years, technology has been developed to improve the accuracy and thereby the safety of cervical pedicle screw placement over traditional fluoroscopic techniques, including intraoperative 3D navigation, computer-assisted Systems and 3D template moulds. We have performed a systematic review into the accuracy rates of the various systems. Methods: The PubMed and Cochrane Library databases were searched for eligible papers; 9 valid papers involving 1427 screws were found. Results: fluoroscopic methods achieved an 80.6% accuracy and navigation methods produced 91.4% and 96.7% accuracy for templates. Conclusion: Navigation methods are significantly more accurate than fluoroscopy, they reduce radiation exposure to the surgical team, and improvements in technology are speeding up operating times. Significantly superior results for templates over fluoroscopy and navigation are complemented by reduced radiation exposure to patient and surgeon; however, the technology requires a more invasive approach, prolonged pre-operative planning and the development of an infrastructure to allow for their rapid production and delivery. We affirm the superiority of navigation over other methods for providing the most accurate and the safest cervical pedicle screw instrumentation, as it is more accurate than fluoroscopy and lacks the limitations of templates.

Accuracy of Robotic-Assisted Spinal Surgery-Comparison to TJR Robotics, da Vinci Robotics, and Optoelectronic Laboratory Robotics

BACKGROUND

The optoelectronic camera source and data interpolation serve as the foundation for navigational integrity in the robotic-assisted surgical platform. The objective of the current systematic review serves to provide a basis for the numerical disparity that exists when comparing the intrinsic accuracy of optoelectronic cameras: accuracy observed in the laboratory setting versus accuracy in the clinical operative environment. It is postulated that there exists a greater number of connections in the optoelectronic kinematic chain when analyzing the clinical operative environment to the laboratory setting. This increase in data interpolation, coupled with intraoperative workflow challenges, reduces the degree of accuracy based on surgical application and to that observed in controlled musculoskeletal kinematic laboratory investigations.

METHODS

Review of the PubMed and Cochrane Library research databases was performed. The exhaustive literature compilation obtained was then vetted to reduce redundancies and categorized into topics of intrinsic optoelectronic accuracy, registration accuracy, musculoskeletal kinematic platforms, and clinical operative platforms.

RESULTS

A total of 147 references make up the basis for the current analysis. Regardless of application, the common denominators affecting overall optoelectronic accuracy are intrinsic accuracy, registration accuracy, and application accuracy. Intrinsic accuracy of optoelectronic tracking equaled or was less than 0.1 mm of translation and 0.1° of rotation per fiducial. Controlled laboratory platforms reported 0.1 to 0.5 mm of translation and 0.1°-1.0° of rotation per array. There is a huge falloff in clinical applications: accuracy in robotic-assisted spinal surgery reported 1.5 to 6.0 mm of translation and 1.5° to 5.0° of rotation when comparing planned to final implant position. Total Joint Robotics and da Vinci urologic robotics computed accuracy, as predicted, lies between these two extremes-1.02 mm for da Vinci and 2 mm for MAKO.

CONCLUSIONS

Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of robotic-assisted spinal surgery. Transitioning from controlled laboratory to clinical operative environments requires an increased number of steps in the optoelectronic kinematic chain and error potential. Diligence in planning, fiducial positioning, system registration, and intraoperative workflow have the potential to improve accuracy and decrease disparity between planned and final implant position. The key determining factors limiting navigation resolution accuracy are highlighted by this Cochrane research analysis.

Prevalence of spine surgery navigation techniques and availability in Africa: A cross-sectional study

Background

Africa has a large burden of spine pathology but has limited and insufficient infrastructure to manage these spine disorders. Therefore, we conducted this e-survey to assess the prevalence and identify the determinants of the availability of spine surgery navigation techniques in Africa.

Materials and methods

A two-part questionnaire was disseminated amongst African neurological and orthopedic surgery consultants and trainees from January 24 to February 23, 2021. The Chi-Square, Fisher Exact, and Kruskal-Wallis tests were used to evaluate bivariable relationships, and a p-value <0.05 was considered statistically significant.

Results

We had 113 respondents from all regions of Africa. Most (86.7 %) participants who practiced or trained in public centers and centers had an annual median spine case surgery volume of 200 (IQR = 190) interventions. Fluoroscopy was the most prevalent spine surgery navigation technique (96.5 %), followed by freehand (55.8 %), stereotactic without intraoperative CT scan (31.9 %), robotic with intraoperative CT scan (29.2 %), stereotactic with intraoperative CT scan (8.8 %), and robotic without intraoperative CT scan (6.2 %). Cost of equipment (94.7 %), lack of trained staff to service (63.7 %), or run the equipment (60.2 %) were the most common barriers to the availability of spine instrumentation navigation. In addition, there were significant regional differences in access to trained staff to run and service the equipment (P = 0.001).

Conclusion

There is a need to increase access to more advanced navigation techniques, and we identified the determinants of availability.

•

African spine surgery has regional disparities in navigation techniques.

•

Fluoroscopy is the most prevalent navigation technique.

•

Cost and lack of trained personnel are the most significant barriers.

Intraoperative hyperspectral label-free imaging: from system design to first-in-patient translation

Despite advances in intraoperative surgical imaging, reliable discrimination of critical tissue during surgery remains challenging. As a result, decisions with potentially life-changing consequences for patients are still based on the surgeon's subjective visual assessment. Hyperspectral imaging (HSI) provides a promising solution for objective intraoperative tissue characterisation, with the advantages of being non-contact, non-ionising and non-invasive. However, while its potential to aid surgical decision-making has been investigated for a range of applications, to date no real-time intraoperative HSI (iHSI) system has been presented that follows critical design considerations to ensure a satisfactory integration into the surgical workflow. By establishing functional and technical requirements of an intraoperative system for surgery, we present an iHSI system design that allows for real-time wide-field HSI and responsive surgical guidance in a highly constrained operating theatre. Two systems exploiting state-of-the-art industrial HSI cameras, respectively using linescan and snapshot imaging technology, were designed and investigated by performing assessments against established design criteria and ex vivo tissue experiments. Finally, we report the use of our real-time iHSI system in a clinical feasibility case study as part of a spinal fusion surgery. Our results demonstrate seamless integration into existing surgical workflows.

Unplanned return to the operating room (UPROR) after surgery for adolescent idiopathic scoliosis

STUDY DESIGN

Retrospective analysis of a prospectively collected multi-center database.

PURPOSE

UPROR (Unplanned Return to the Operating Room) is an inclusive metric for unexpected surgery after the index procedure. Given the many quality and safety improvements in AIS surgery over the past 20 years, it is useful for spine deformity surgeons to understand the current rate of UPROR, the etiologies, and trends over time. A report from a very large data set, including multiple surgeons and centers, with longer follow-up, would provide the clearest picture.

METHODS

We performed a retrospective review of a prospective multi-center database of patients who had AIS deformity correction surgery to analyze all cases of UPROR, using linear regression models, survival analysis, and descriptive statistics.

RESULTS

Among 3464 patients who had surgery (ASF, PSF, or ASF + PSF) for AIS from 1995 to 2017, 4.8% had an UPROR event in one of the following categories: surgical-site-related (43.3%), instrument failures (34.3%), revisions (8.4%), neurologic (5.1%), pulmonary (5.1%), medical (0.6%), and other (3.4%). The average time from initial surgery to UPROR was 734.4 days. 45.5% of UPRORs occurred within 1 year, 12.4% between 1 and 2 years, 30.9% between 2 and 5 years, and 11.2% between 5 and 10 years. In patients with at least 2-year, 5-year, and 10-year follow-up, the UPROR rates were 6.6, 7.3, and 9.2%, respectively. Between 1997 and 2013, the UPROR rate decreased by 0.46% per year (95% CI 0.25-0.68, p < 0.001).

CONCLUSION

UPROR has decreased significantly over time but as expected, increases with increased follow-up.

LEVEL OF EVIDENCE

Level III, therapeutic.

Incorporating New Technologies to Overcome the Limitations of Endoscopic Spine Surgery: Navigation, Robotics, and Visualization

Recently, spine surgery has gradually evolved from conventional open surgery to minimally invasive surgery, and endoscopic spine surgery (ESS) has become an important procedure in minimally invasive spine surgery. With improvements in the optics, spine endoscope, endoscopic burr, and irrigation pump, the indications of ESS are gradually widening from lumbar to cervical and thoracic spine. ESS was not only used previously for disc herniations that were contained without migration but is also used currently for highly migrated disc herniations and spinal stenosis; thus, the indications of ESS will be further expanded. Although ESS has certain advantages such as less soft tissue dissection and muscle trauma, reduced blood loss, less damage to the epidural blood supply and consequent less epidural fibrosis and scarring, reduced hospital stay, early functional recovery, and improvement of quality of life as well as better cosmesis, several obstacles remain for ESS to be widespread because it has a steep learning curve and surgical outcome is strongly dependent on the surgeon's skillfulness. A solid surgical technique requires reproducibility and ensured safety in addition to surgical outcomes. In this review article, how to improve ESS was investigated by grafting novel technologies such as navigation, robotics, and 3-dimensional and ultraresolution visualization.

The Use of Skin Staples as Fiducial Markers to Confirm Intraoperative Spinal Navigation Registration and Accuracy

BACKGROUND

With the advent of intraoperative computed tomography (CT) for image guidance, numerous examples of accurate navigation being applied to cranial and spinal pathology have come to light. For spinal disorders, the utilization of image guidance for the placement of percutaneous spinal instrumentation, complex osteotomies, and minimally invasive approaches are frequently utilized in trauma, degenerative, and oncological pathologies. The use of intraoperative CT for navigation, however, requires a low target registration error that must be verified throughout the procedure to confirm the accuracy of image guidance.

OBJECTIVE

To present the use of skin staples as a sterile, economical fiducial marker for minimally invasive spinal procedures requiring intraoperative CT navigation.

METHODS

Staples are applied to the skin prior to obtaining the registration CT scan and maintained throughout the remainder of the surgery to facilitate confirmation of image guidance accuracy.

RESULTS

This low-cost, simple, sterile approach provides surface landmarks that allow reliable verification of navigation accuracy during percutaneous spinal procedures using intraoperative CT scan image guidance.

CONCLUSION

The utilization of staples as a fiducial marker represents an economical and easily adaptable technique for ensuring accuracy of image guidance with intraoperative CT navigation.

Radiotherapy and Surgical Advances in the Treatment of Metastatic Spine Tumors: A Narrative Review

Spine tumors encompass a wide range of diseases with a commensurately broad spectrum of available treatments, ranging from radiation for spinal metastases to highly invasive en bloc resection for primary vertebral column malignancies. This high variability in treatment approaches stems both from variability in the goals of surgery (e.g., oncologic cure vs. symptom palliation) and from the significant advancements in surgical technologies that have been made over the past 2 decades. Among these advancements are improvements in surgical technique, namely minimally invasive approaches, increased availability of focused radiation modalities (e.g., proton therapy and linear accelerator devices), and new surgical technologies, such as carbon fiber-reinforced polyether ether ketone rods. In addition, several groups have described nonsurgical interventions, such as vertebroplasty and kyphoplasty for spinal instability secondary to pathologic fracture, and lesion ablation with spinal laser interstitial thermoablation, radiofrequency ablation, or cryoablation. We provide an overview of the latest technological advancements in spinal oncology and their potential usefulness for modern spinal oncologists.

Drill-mounted video guidance for orthopaedic trauma surgery

Purpose: Percutaneous fracture fixation is a challenging procedure that requires accurate interpretation of fluoroscopic images to insert guidewires through narrow bone corridors. We present a guidance system with a video camera mounted onboard the surgical drill to achieve real-time augmentation of the drill trajectory in fluoroscopy and/or CT. Approach: The camera was mounted on the drill and calibrated with respect to the drill axis. Markers identifiable in both video and fluoroscopy are placed about the surgical field and co-registered by feature correspondences. If available, a preoperative CT can also be co-registered by 3D-2D image registration. Real-time guidance is achieved by virtual overlay of the registered drill axis on fluoroscopy or in CT. Performance was evaluated in terms of target registration error (TRE), conformance within clinically relevant pelvic bone corridors, and runtime. Results: Registration of the drill axis to fluoroscopy demonstrated median TRE of 0.9 mm and 2.0 deg when solved with two views (e.g., anteroposterior and lateral) and five markers visible in both video and fluoroscopy-more than sufficient to provide Kirschner wire (K-wire) conformance within common pelvic bone corridors. Registration accuracy was reduced when solved with a single fluoroscopic view ( TRE = 3.4    mm and 2.7 deg) but was also sufficient for K-wire conformance within pelvic bone corridors. Registration was robust with as few as four markers visible within the field of view. Runtime of the initial implementation allowed fluoroscopy overlay and/or 3D CT navigation with freehand manipulation of the drill up to 10    frames / s . Conclusions: A drill-mounted video guidance system was developed to assist with K-wire placement. Overall workflow is compatible with fluoroscopically guided orthopaedic trauma surgery and does not require markers to be placed in preoperative CT. The initial prototype demonstrates accuracy and runtime that could improve the accuracy of K-wire placement, motivating future work for translation to clinical studies.

Image-Guided Tethering Spine Surgery With Outcome Prediction Using Spatio-Temporal Dynamic Networks

Recent fusionless surgical techniques for corrective spine surgery such as Anterior Vertebral Body Growth Modulation (AVBGM) allow to treat mild to severe spinal deformations by tethering vertebral bodies together, helping to preserve lower back flexibility. Forecasting the outcome of AVBGM from skeletally immature patients remains elusive with several factors involved in corrective vertebral tethering, but could help orthopaedic surgeons plan and tailor AVBGM procedures prior to surgery. We introduce an intra-operative framework forecasting the outcomes during AVBGM surgery in scoliosis patients. The method is based on spatial-temporal corrective networks, which learns the similarity in segmental corrections between patients and integrates a long-term shifting mechanism designed to cope with timing differences in onset to surgery dates, between patients in the training set. The model captures dynamic geometric dependencies in scoliosis patients, ensuring long-term dependency with temporal dynamics in curve evolution and integrated features from inter-vertebral disks extracted from T2-w MRI. The loss function of the network introduces a regularization term based on learned group-average piecewise-geodesic path to ensure the generated corrective transformations are coherent with regards to the observed evolution of spine corrections at follow-up exams. The network was trained on 695 3D spine models and tested on 72 operative patients using a set of 3D spine reconstructions as inputs. The spatio-temporal network predicted outputs with errors of 1.8 ± 0.8mm in 3D anatomical landmarks, yielding geometries similar to ground-truth spine reconstructions obtained at one and two year follow-ups and with significant improvements to comparative deep learning and biomechanical models.

Multi-view 3D skin feature recognition and localization for patient tracking in spinal surgery applications

BACKGROUND

Minimally invasive spine surgery is dependent on accurate navigation. Computer-assisted navigation is increasingly used in minimally invasive surgery (MIS), but current solutions require the use of reference markers in the surgical field for both patient and instruments tracking.

PURPOSE

To improve reliability and facilitate clinical workflow, this study proposes a new marker-free tracking framework based on skin feature recognition.

METHODS

Maximally Stable Extremal Regions (MSER) and Speeded Up Robust Feature (SURF) algorithms are applied for skin feature detection. The proposed tracking framework is based on a multi-camera setup for obtaining multi-view acquisitions of the surgical area. Features can then be accurately detected using MSER and SURF and afterward localized by triangulation. The triangulation error is used for assessing the localization quality in 3D.

RESULTS

The framework was tested on a cadaver dataset and in eight clinical cases. The detected features for the entire patient datasets were found to have an overall triangulation error of 0.207 mm for MSER and 0.204 mm for SURF. The localization accuracy was compared to a system with conventional markers, serving as a ground truth. An average accuracy of 0.627 and 0.622 mm was achieved for MSER and SURF, respectively.

CONCLUSIONS

This study demonstrates that skin feature localization for patient tracking in a surgical setting is feasible. The technology shows promising results in terms of detected features and localization accuracy. In the future, the framework may be further improved by exploiting extended feature processing using modern optical imaging techniques for clinical applications where patient tracking is crucial.

The Use of Image-Guided Navigation Systems During Spine Surgeries in Saudi Arabia: A Cross-Sectional Study

BACKGROUND

We used a cross-sectional study design (questionnaire) to investigate the use of image-guided navigation (IGN) in Saudi Arabia and explore possible differences in implementing IGN for daily practice.

METHODS

An internet-based survey was sent to all spine surgeons who are practicing in Saudi Arabia (orthopedics or neurosurgery). The survey is composed of 12 items that collected demographic and academic data.

RESULTS

Ninety-nine answered the questionnaire from 197; 80% were from Riyadh, the capital, and 50% were consultants (attending physicians). Orthopedic surgeons were almost 60% of responders compared to 40% neurosurgeons. The use of navigation in Saudi hospitals was high (76.8%). There was a significant difference between specialties in the preference of using navigation (23.2% for orthopedics versus 81.4% for neurosurgery, P < .001) and routine use in surgical spine cases (88.4% for neurosurgery versus 50.0% orthopedics, P < .001). The majority of responders from neurosurgery learned to use navigation during residency compared to orthopedics responders (51.2% versus 28.6%, P = .001). More than 30% of orthopedics responders expressed they never learned navigation compared to only 4% of neurosurgery responders. The comfort level of > 75% with performing surgery using navigation was significantly different between specialties (25% for orthopedics versus 46.5% for neurosurgery, P < .001).

CONCLUSION

Saudi spine surgeons are among the highest users of IGN systems. The strong healthcare infrastructure and the availability of these devices across the country are among the most important factors for its prevalence. Enhancing surgical exposure and education of postgraduate trainees to use these tools, especially within orthopedics, could increase use and comfort level rates.

Percutaneous, Navigated Minimally Invasive Posterior Cervical Pedicle Screw Fixation

BACKGROUND

Cervical pedicle screws provide significant biomechanical advantage but can be technically challenging and associated with morbid exposure. Improvements in intraoperative navigation guidance and instrumentation have made feasible this biomechanically robust, but technically challenging procedure. We present our initial experience with minimally invasive (MIS) percutaneous pedicle screw fixation in the cervical atlantoaxial and subaxial spine.

METHODS

A retrospective review was performed on 27 cases that involved a novel MIS percutaneous cervical pedicle screw technique. Small lateral skin incisions were made bilaterally on the neck using intraoperative navigation guidance. Subsequently, navigated, percutaneous screws were placed using the Proficient Minimally Invasive System (PROMIS; Spine Wave, Shelton, CT). Computed tomography (CT)-guided navigation was used for cervical pedicle screw placement with subsequent placement of percutaneous rods.

RESULTS

Indications for surgery included type II odontoid fractures, subaxial fracture dislocations and burst fracture, metastatic pathological burst fracture, and degenerative spondylosis with stenosis. There were 15 men and 12 women, with an average age 63.5 years. Follow-up ranged from 3 to 24 months (average = 16.7 months). One screw was revised intraoperatively. Two patients (7.7%) required reoperation, 1 patient required repositioning of a C5 pedicle screw, and 1 suffered a C7 body fracture. No nerve root injury, spinal cord injury, or vertebral artery injuries were reported.

CONCLUSIONS

Percutaneous cervical pedicle screw fixation is a feasible and safe technique when performed with CT-guided intraoperative navigation techniques. Cervical pedicle screw fixation provides a biomechanically superior construct in comparison with a lateral mass technique. In addition, the lack of paraspinal muscle disruption preserves important stabilizers of the posterior ligamentous complex and may reduce wound-healing issues in high-risk cases (eg, trauma patients). Although the current role for percutaneous instrumentation is relatively narrow, the advancement of MIS posterior cervical techniques may provide expanded opportunities in the future.

Guidelines for navigation-assisted spine surgery

Spinal surgery is a technically demanding and challenging procedure because of the complicated anatomical structures of the spine and its proximity to several important tissues. Surgical landmarks and fluoroscopy have been used for pedicle screw insertion but are found to produce inaccuracies in placement. Improving the safety and accuracy of spinal surgery has increasingly become a clinical concern. Computerassisted navigation is an extension and application of precision medicine in orthopaedic surgery and has significantly improved the accuracy of spinal surgery. However, no clinical guidelines have been published for this relatively new and fast-growing technique, thus potentially limiting its adoption. In accordance with the consensus of consultant specialists, literature reviews, and our local experience, these guidelines include the basic concepts of the navigation system, workflow of navigation-assisted spinal surgery, some common pitfalls, and recommended solutions. This work helps to standardize navigation-assisted spinal surgery, improve its clinical efficiency and precision, and shorten the clinical learning curve.

To Align Multimodal Lumbar Spine Images via Bending Energy Constrained Normalized Mutual Information

To align multimodal images is important for information fusion, clinical diagnosis, treatment planning, and delivery, while few methods have been dedicated to matching computerized tomography (CT) and magnetic resonance (MR) images of lumbar spine. This study proposes a coarse-to-fine registration framework to address this issue. Firstly, a pair of CT-MR images are rigidly aligned for global positioning. Then, a bending energy term is penalized into the normalized mutual information for the local deformation of soft tissues. In the end, the framework is validated on 40 pairs of CT-MR images from our in-house collection and 15 image pairs from the SpineWeb database. Experimental results show high overlapping ratio (in-house collection, vertebrae 0.97 ± 0.02, blood vessel 0.88 ± 0.07; SpineWeb, vertebrae 0.95 ± 0.03, blood vessel 0.93 ± 0.10) and low target registration error (in-house collection, ≤2.00 ± 0.62 mm; SpineWeb, ≤2.37 ± 0.76 mm) are achieved. The proposed framework concerns both the incompressibility of bone structures and the nonrigid deformation of soft tissues. It enables accurate CT-MR registration of lumbar spine images and facilitates image fusion, spine disease diagnosis, and interventional treatment delivery.

Towards Optical Imaging for Spine Tracking without Markers in Navigated Spine Surgery

Surgical navigation systems are increasingly used for complex spine procedures to avoid neurovascular injuries and minimize the risk for reoperations. Accurate patient tracking is one of the prerequisites for optimal motion compensation and navigation. Most current optical tracking systems use dynamic reference frames (DRFs) attached to the spine, for patient movement tracking. However, the spine itself is subject to intrinsic movements which can impact the accuracy of the navigation system. In this study, we aimed to detect the actual patient spine features in different image views captured by optical cameras, in an augmented reality surgical navigation (ARSN) system. Using optical images from open spinal surgery cases, acquired by two gray-scale cameras, spinal landmarks were identified and matched in different camera views. A computer vision framework was created for preprocessing of the spine images, detecting and matching local invariant image regions. We compared four feature detection algorithms, Speeded Up Robust Feature (SURF), Maximal Stable Extremal Region (MSER), Features from Accelerated Segment Test (FAST), and Oriented FAST and Rotated BRIEF (ORB) to elucidate the best approach. The framework was validated in 23 patients and the 3D triangulation error of the matched features was < 0 . 5 mm. Thus, the findings indicate that spine feature detection can be used for accurate tracking in navigated surgery.

Diffuse reflectance spectroscopy for breach detection during pedicle screw placement: a first in vivo investigation in a porcine model

Background

The safe and accurate placement of pedicle screws remains a critical step in open and minimally invasive spine surgery, emphasizing the need for intraoperative guidance techniques. Diffuse reflectance spectroscopy (DRS) is an optical sensing technology that may provide intraoperative guidance in pedicle screw placement.

Purpose

The study presents the first in vivo minimally invasive procedure using DRS sensing at the tip of a Jamshidi needle with an integrated optical K-wire. We investigate the effect of tissue perfusion and probe-handling conditions on the reliability of fat fraction measurements for breach detection in vivo.

Methods

A Jamshidi needle with an integrated fiber-optic K-wire was gradually inserted into the vertebrae under intraoperative image guidance. The fiber-optic K-wire consisted of two optical fibers with a fiber-to-fiber distance of 1.024 mm. DRS spectra in the wavelength range of 450 to 1600 nm were acquired at several positions along the path inside the vertebrae. Probe-handling conditions were varied by changing the amount of pressure exerted on the probe within the vertebrae. Continuous spectra were recorded as the probe was placed in the center of the vertebral body while the porcine specimen was sacrificed via a lethal injection.

Results

A typical insertion of the fiber-optic K-wire showed a drop in fat fraction during an anterior breach as the probe transitioned from cancellous to cortical bone. Fat fraction measurements were found to be similar irrespective of the amount of pressure exerted on the probe (p = 0.65). The 95% confidence interval of fat fraction determination was found in the narrow range of 1.5–3.6% under various probe-handling conditions. The fat fraction measurements remained stable during 70 min of decreased blood flow after the animal was sacrificed.

Discussions

These findings indicate that changes in tissue perfusion and probe-handling conditions have a relatively low measureable effect on the DRS signal quality and thereby on the determination of fat fraction as a breach detection signal.

Conclusions

Fat fraction quantification for intraoperative pedicle screw breach detection is reliable, irrespective of changes in tissue perfusion and probe-handling conditions.

Cone-beam CT for imaging of the head/brain: Development and assessment of scanner prototype and reconstruction algorithms

PURPOSE

Our aim was to develop a high-quality, mobile cone-beam computed tomography (CBCT) scanner for point-of-care detection and monitoring of low-contrast, soft-tissue abnormalities in the head/brain, such as acute intracranial hemorrhage (ICH). This work presents an integrated framework of hardware and algorithmic advances for improving soft-tissue contrast resolution and evaluation of its technical performance with human subjects.

METHODS

Four configurations of a CBCT scanner prototype were designed and implemented to investigate key aspects of hardware (including system geometry, antiscatter grid, bowtie filter) and technique protocols. An integrated software pipeline (c.f., a serial cascade of algorithms) was developed for artifact correction (image lag, glare, beam hardening and x-ray scatter), motion compensation, and three-dimensional image (3D) reconstruction [penalized weighted least squares (PWLS), with a hardware-specific statistical noise model]. The PWLS method was extended in this work to accommodate multiple, independently moving regions with different resolution (to address both motion compensation and image truncation). Imaging performance was evaluated quantitatively and qualitatively with 41 human subjects in the neurosciences critical care unit (NCCU) at our institution.

RESULTS

The progression of four scanner configurations exhibited systematic improvement in the quality of raw data by variations in system geometry (source-detector distance), antiscatter grid, and bowtie filter. Quantitative assessment of CBCT images in 41 subjects demonstrated: ~70% reduction in image nonuniformity with artifact correction methods (lag, glare, beam hardening, and scatter); ~40% reduction in motion-induced streak artifacts via the multi-motion compensation method; and ~15% improvement in soft-tissue contrast-to-noise ratio (CNR) for PWLS compared to filtered backprojection (FBP) at matched resolution. Each of these components was important to improve contrast resolution for point-of-care cranial imaging.

CONCLUSIONS

This work presents the first application of a high-quality, point-of-care CBCT system for imaging of the head/ brain in a neurological critical care setting. Hardware configuration iterations and an integrated software pipeline for artifacts correction and PWLS reconstruction mitigated artifacts and noise to achieve image quality that could be valuable for point-of-care detection and monitoring of a variety of intracranial abnormalities, including ICH and hydrocephalus.

Imaging Technologies in Spine Surgery

This article presents a comprehensive review of the evolution of both invasive and noninvasive imaging technologies that are part of the arsenal of spinal diagnostics and surgical therapy. The text provides not only a historical lens to the evolution of the imaging technologies that are part of routine contemporary practice but also provides a detailed sketch of emerging imaging technologies, such as endoscopic and exoscopic systems. Augmented reality, virtual reality, and mixed reality are new technologies that have enhanced the preparation of surgery and provide excellent case-specific training modules to break down each step of an operation in isolation.

Conventional versus stereotactic image guided pedicle screw placement during spinal deformity correction: a retrospective propensity score-matched study of a national longitudinal database

PURPOSE/AIM

To compare complications, readmissions, revisions, and payments between navigated and conventional pedicle screw fixation for treatment of spine deformity.

METHODS

The Thomson Reuters MarketScan national longitudinal database was used to identify patients undergoing osteotomy, posterior instrumentation, and fusion for treatment of spinal deformity with or without image-guided navigation between 2007-2016. Conventional and navigated groups were propensity-matched (1:1) to normalize differences between demographics, comorbidities, and surgical characteristics. Clinical outcomes and charges were compared between matched groups using bivariate analyses.

RESULTS

A total of 4,604 patients were identified as having undergone deformity correction, of which 286 (6.2%) were navigated. Propensity-matching resulted in a total of 572 well-matched patients for subsequent analyses, of which half were navigated. Rate of mechanical instrumentation-related complications was found to be significantly lower for navigated procedures (p = 0.0371). Navigation was also associated with lower rates of 90-day unplanned readmissions (p = 0.0295), as well as 30- and 90-day postoperative revisions (30-day: p = 0.0304, 90-day: p = 0.0059). Hospital, physician, and total payments favored the conventional group for initial admission (p = 0.0481, 0.0001, 0.0019, respectively); however, when taking into account costs of readmissions, hospital payments became insignificantly different between the two groups.

CONCLUSIONS

Procedures involving image-guided navigation resulted in decreased instrumentation-related complications, unplanned readmissions, and postoperative revisions, highlighting its potential utility for the treatment of spine deformity. Future advances in navigation technologies and methodologies can continue to improve clinical outcomes, decrease costs, and facilitate widespread adoption of navigation for deformity correction.

Stereotactic Navigation for Rectal Surgery: Comparison of 3-Dimensional C-Arm-Based Registration to Paired-Point Registration

BACKGROUND

Stereotactic navigation enables surgeons to use the preoperative CT or MRI images as a real-time "navigation map." Although stereotactic navigation has been established in neurosurgery and orthopedic surgery, whether this technology is applicable to GI tract surgery remains challenging because of tissue deformation and organ motion. A critical component of this technology is the registration that links the patient's actual body to the preoperative imaging data.

OBJECTIVE

The objective was to assess the applicability of stereotactic navigation in rectal surgery, focusing on the registration method.

DESIGN

This study was based on a prospective case series.

SETTING

The study was conducted in a single university hospital.

PATIENTS

Four patients who underwent laparoscopic rectal surgery were included.

INTERVENTIONS

Paired-point registration was performed for 2 cases, whereas 3-dimensional C-arm-based registration was performed for the other 2 cases. In addition, 3-dimensional C-arm-based registration was performed twice during the operation.

MAIN OUTCOME MEASURE

Navigation accuracy was evaluated by measuring target registration error at 8 anatomical landmarks.

RESULTS

Target registration error of the 3-dimensional C-arm-based registration group was significantly smaller than that of the paired-point registration group (median, 19.5 mm vs 54.1 mm; p < 0.001). In particular, the error of Z-axis (cranial-to-caudal direction) was significantly smaller in 3-dimensional C-arm-based registration (median, 12.4 mm vs 48.8 mm; p < 0.001). In one case in the 3-dimensional C-arm-based registration group, target registration error of the second registration became significantly smaller than that of the first registration (p = 0.008).

LIMITATIONS

This was an observational study with small sample size.

CONCLUSION

Three-dimensional C-arm-based registration could be performed with the patient in a lithotomy position with head down and lateral tilt without being affected by positional changes. Three-dimensional C-arm-based registration resulted in significantly higher navigation accuracy than paired-point registration, and its accuracy could be further improved by intraoperative re-registration.

Accuracy of augmented reality surgical navigation for minimally invasive pedicle screw insertion in the thoracic and lumbar spine with a new tracking device

BACKGROUND CONTEXT

Minimally invasive approaches are increasingly used in spine surgery. The purpose of navigation systems is to guide the surgeon and to reduce intraoperative x-ray exposure.

PURPOSE

This study aimed to determine the feasibility and clinical accuracy of a navigation technology based on augmented reality surgical navigation (ARSN) for minimally invasive thoracic and lumbar pedicle screw instrumentation compared with standard fluoroscopy-guided minimally invasive technique.

STUDY DESIGN/SETTING

Cadaveric laboratory study.

METHODS

ARSN was installed in a hybrid operating room, consisting of a flat panel detector c-arm with two dimensional/three dimensional imaging capabilities and four integrated cameras in its frame. The surface-referenced navigation device does not require a bony reference but uses video cameras and optical markers applied to the patient's skin for tracking. In four cadavers, a total of 136 pedicle screws were inserted in thoracic and lumbar vertebrae. The accuracy was assessed by three independent raters in postoperative conventional computed tomography.

RESULTS

The overall accuracy of ARSN was 94% compared with an accuracy of 88% for fluoroscopy. The difference was not statistically significant. In the thoracic region, accuracy with ARSN was 92% compared with 83% with fluoroscopy. With fluoroscopy, unsafe screws were observed in three normal cadavers and one with scoliosis. Using ARSN, unsafe screws were only observed in the scoliotic spine. No significant difference in the median of time for K-wire placement was recorded. As no intraoperative fluoroscopy was necessary in ARSN, the performing surgeon was not exposed to radiation.

CONCLUSIONS

In this limited cadaveric study minimally invasive screw placement using ARSN was demonstrated to be feasible and as accurate as fluoroscopy. It did not require any additional navigation time or use of any intraoperative x-ray imaging, thereby potentially permitting surgery in a protective lead garment-free environment. A well-powered clinical study is needed to demonstrate a significant difference in the accuracy between the two methods.

CLINICAL SIGNIFICANCE

ARSN offers real-time imaging of planned insertion paths, instrument tracking, and overlay of three dimensional bony anatomy and surface topography. The referencing procedure, by optical recognition of several skin markers is easy and does not require a solid bony reference as necessary for conventional navigation which saves time. Additionally, ARSN may foster the reduction of intraoperative x-ray exposure to spinal surgeons.

The Role of Minimal Access Surgery in the Treatment of Spinal Metastatic Tumors

STUDY DESIGN

Literature review.

OBJECTIVE

To provide an overview of the recent advances in minimal access surgery (MAS) for spinal metastases.

METHODS

Literature review.

RESULTS

Experience gained from MAS in the trauma, degenerative and deformity settings has paved the road for MAS techniques for spinal cancer. Current MAS techniques for the treatment of spinal metastases include percutaneous instrumentation, mini-open approaches for decompression and tumor resection with or without tubular/expandable retractors and thoracoscopy/endoscopy. Cancer care requires a multidisciplinary effort and adherence to treatment algorithms facilitates decision making, ultimately improving patient outcomes. Specific algorithms exist to help guide decisions for MAS for extradural spinal metastases. One major paradigm shift has been the implementation of percutaneous stabilization for treatment of neoplastic spinal instability. Percutaneous stabilization can be enhanced with cement augmentation for increased durability and pain palliation. Unlike osteoporotic fractures, kyphoplasty and vertebroplasty are known to be effective therapies for symptomatic pathologic compression fractures as supported by high level evidence. The integration of systemic body radiation therapy for spinal metastases has eliminated the need for aggressive tumor resection allowing implementation of MAS epidural tumor decompression via tubular or expandable retractors and preliminary data exist regarding laser interstitial thermal therapy and radiofrequency ablation for tumor control. Neuronavigation and robotic systems offer increased precision, facilitating the role of MAS for spinal metastases.

CONCLUSIONS

MAS has a significant role in the treatment of spinal metastases. This review highlights the current utilization of minimally invasive surgical strategies for treatment of spinal metastases.

Traumatic Sacral Fractures: Navigation Technique in Instrumented Stabilization

BACKGROUND

Sacral fractures are a challenge regarding treatment and classification. Surgical techniques using spinal navigation systems can improve treatment, especially if used in collaboration among different specialists.

METHODS

Between 2015 and 2017, we treated 25 consecutive cases of sacral fracture. Twelve patients (48%) underwent mechanical ventilation due to hypovolemic shock for severe thoracoabdominal trauma; bleeding was blocked with pelvic packing in 9 cases (36%) and transcatheter embolization in 2 cases (8%). External fixation was used in 7 cases (28%). In 20 cases (80%) spinal fractures were associated. All patients were operated on using spinal navigation by a team of neurosurgeons and orthopedic surgeons.

RESULTS

The mean time from first observation to surgery was 18 days (range 8-31). Surgical treatment consisted of iliosacral fixation in 19 cases (76%) and spinopelvic fixation in 6 cases (24%). The mean number of screws for spinopelvic fixation was 9.67 (range 6-17) with a mean operation time of 323.67 minutes (range 247-471); in iliosacral osteosynthesis the mean screw number was 1.37 (range 1-3) and mean surgical time was 78.93 minutes (range 61-130). Postoperative computed tomography showed the correct screw placement. Wound infection occurred in 2 cases (8%), managed with vacuum-assisted closure therapy; in 1 case (4%) a sacral screw was removed for decubitus.

CONCLUSIONS

Navigation systems in instrumented spinopelvic and sacropelvic reconstruction provide greater safety, reducing learning times and malpositioning. Multidisciplinary management allows us to achieve optimal results, especially when the sacral fracture is combined with spinal and pelvic lesions. The use of navigation systems could represent an important advancement.

Machine vision augmented reality for pedicle screw insertion during spine surgery

Implementing pedicle safe zones with augmented reality has the potential to improve operating room workflow during pedicle screw insertion. These safe zones will allow for image guidance when tracked instruments are unavailable. Using the correct screw trajectory as a reference angle for a successful screw insertion, we will determine the angles which lead to medial, lateral, superior and inferior breaches. These breaches serve as the boundaries of the safe zones. Measuring safe zones from the view of the surgical site and comparing to the radiological view will further understand the visual relationship between the radiological scans and the surgical site. Safe zones were measured on a spine phantom and were then replicated on patients. It was found that the largest causes for variance was between each of the camera views and the radiological views. The differences between the left and right cameras were insignificant. Overall, the camera angles appeared to be larger than the radiological angles. The magnification effect found in the surgical site result in an increased level of angle sensitivity for pedicle screw insertion techniques. By designing a virtual road map on top of the surgical site directly using tracked tools, the magnification effect is already taken into consideration during surgery. Future initiatives include the use of an augmented reality headset.