Neuronavigation in minimally invasive spine surgery

Image-Guided Navigation in Spine Surgery: From Historical Developments to Future Perspectives

Intraoperative navigation is critical during spine surgery to ensure accurate instrumentation placement. From the early era of fluoroscopy to the current advancement in robotics, spinal navigation has continued to evolve. By understanding the variations in system protocols and their respective usage in the operating room, the surgeon can use and maximize the potential of various image guidance options more effectively. At the same time, maintaining navigation accuracy throughout the procedure is of the utmost importance, which can be confirmed intraoperatively by using an internal fiducial marker, as demonstrated herein. This technology can reduce the need for revision surgeries, minimize postoperative complications, and enhance the overall efficiency of operating rooms.

TomoRay: Generating Synthetic Computed Tomography of the Spine From Biplanar Radiographs

OBJECTIVE

Computed tomography (CT) imaging is a cornerstone in the assessment of patients with spinal trauma and in the planning of spinal interventions. However, CT studies are associated with logistical problems, acquisition costs, and radiation exposure. In this proof-of-concept study, the feasibility of generating synthetic spinal CT images using biplanar radiographs was explored. This could expand the potential applications of x-ray machines pre-, post-, and even intraoperatively.

METHODS

A cohort of 209 patients who underwent spinal CT imaging from the VerSe2020 dataset was used to train the algorithm. The model was subsequently evaluated using an internal and external validation set containing 55 from the VerSe2020 dataset and a subset of 56 images from the CTSpine1K dataset, respectively. Digitally reconstructed radiographs served as input for training and evaluation of the 2-dimensional (2D)-to-3-dimentional (3D) generative adversarial model. Model performance was assessed using peak signal to noise ratio (PSNR), structural similarity index (SSIM), and cosine similarity (CS).

RESULTS

At external validation, the developed model achieved a PSNR of 21.139 ± 1.018 dB (mean ± standard deviation). The SSIM and CS amounted to 0.947 ± 0.010 and 0.671 ± 0.691, respectively.

CONCLUSION

Generating an artificial 3D output from 2D imaging is challenging, especially for spinal imaging, where x-rays are known to deliver insufficient information frequently. Although the synthetic CT scans derived from our model do not perfectly match their ground truth CT, our proof-of-concept study warrants further exploration of the potential of this technology.

Longer Screws Decrease the Risk of Radiographic Pseudarthrosis Following Elective Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

In patients undergoing elective anterior cervical discectomy and fusion (ACDF), we sought to determine the impact of screw length on: (1) radiographic pseudarthrosis, (2) pseudarthrosis requiring reoperation, and (3) patient-reported outcome measures (PROMs).

METHODS

A single-institution, retrospective cohort study was undertaken from 2010-21. The primary independent variables were: screw length (mm), screw length divided by the anterior-posterior vertebral body diameter (VB%), and the presence of any screw with VB% < 75% vs all screws with VB% ≥ 75%. Multivariable logistic regression controlled for age, BMI, gender, smoking, American Society of Anesthesiology grade, number of levels fused, and whether a corpectomy was performed.

RESULTS

Of 406 patients undergoing ACDF, levels fused were: 1-level (39.4%), 2-level (42.9%), 3-level (16.7%), and 4-level (1.0%). Mean screw length was 14.3 ± 2.3 mm, and mean VB% was 74.4 ± 11.2. A total of 293 (72.1%) had at least one screw with VB% < 75%, 113 (27.8%) had all screws with VB% ≥ 75%, and 141 (34.7%) patients had radiographic pseudarthrosis at 1-year. Patients who had any screw with VB% < 75% had a higher rate of radiographic pseudarthrosis compared to those had all screws with VB% ≥ 75% (39.6% vs 22.1%, P < .001). Multivariable logistic regression revealed that a higher VB% (OR = .97, 95%CI = .95-.99, P = .035) and having all screws with VB% ≥ 75% (OR = .51, 95%CI = .27-.95, P = .037) significantly decreased the odds of pseudarthrosis at 1-year, with no difference in reoperation or PROMs (all P > .05).

CONCLUSION

Longer screws taking up ≥75% of the vertebral body protected against radiographic pseudarthrosis at 1-year. Maximizing screw length in ACDF is an easily modifiable factor directly under the surgeon's control that may mitigate the risk of pseudarthrosis.

Technical evolution of pediatric neurosurgery: the evolution of intraoperative imaging

Imaging has always been fundamental to neurosurgery, and its evolution over the last century has made a dramatic transformation in the ability of neurosurgeons to define pathology and preserve normal tissue during their operations. In the mid-70 s, the development of computerized cross-sectional imaging with CT scan and subsequently MRI have revolutionized the practice of neurosurgery. Later, further advances in computer technology and medical engineering have allowed the combination of many modalities to bring them into the operating theater. This evolution has allowed real-time intraoperative imaging, in the hope of helping neurosurgeons achieve accuracy, maximal safe resection, and the implementation of minimally invasive techniques in brain and spine pathologies. Augmented reality and robotic technologies are also being applied as useful intra-operative techniques that will improve surgical planning and outcomes in the future. In this article, we will review imaging modalities and provide our institutional perspective on how we have integrated them into our practice.

Man versus machine: Automatic pedicle screw planning using registration-based techniques compared with manual screw planning for thoracolumbar fusion surgeries

OBJECTIVE

This study evaluates the precision of a commercially available spine planning software in automatic spine labelling and screw-trajectory proposal.

METHODS

The software uses automatic segmentation and registration of the vertebra to generate screw proposals. 877 trajectories were compared. Four neurosurgeons assessed suggested trajectories, performed corrections, and manually planned pedicle screws. Additionally, automatic identification/labelling was evaluated.

RESULTS

Automatic labelling was correct in 89% of the cases. 92.9% of automatically planned trajectories were in accordance with G&R grade A + B. Automatic mode reduced the time spent planning screw trajectories by 7 s per screw to 20 s per vertebra. Manual mode yielded differences in screw-length between surgeons (largest distribution peak: 5 mm), automatic in contrast at 0 mm. The size of suggested pedicle screws was significantly smaller (largest peaks in difference between 0.5 and 3 mm) than the surgeon's choice.

CONCLUSION

Automatic identification of vertebrae works in most cases and suggested pedicle screw trajectories are acceptable. So far, it does not substitute for an experienced surgeon's assessment.

Technique for Validation of Intraoperative Navigation in Minimally Invasive Spine Surgery

BACKGROUND

Intraoperative 3-dimensional navigation is an enabling technology that has quickly become a commonplace in minimally invasive spine surgery (MISS). It provides a useful adjunct for percutaneous pedicle screw fixation. Although navigation is associated with many benefits, including improvement in overall screw accuracy, navigation errors can lead to misplaced instrumentation and potential complications or revision surgery. It is difficult to confirm navigation accuracy without a distant reference point.

OBJECTIVE

To describe a simple technique for validating navigation accuracy in the operating room during MISS.

METHODS

The operating room is set up in a standard fashion for MISS with intraoperative cross-sectional imaging available. A 16-gauge needle is placed within the bone of the spinous process before intraoperative cross-sectional imaging. The entry level is chosen such that the space between the reference array and the needle encompasses the surgical construct. Before placing each pedicle screw, accuracy is verified by placing the navigation probe over the needle.

RESULTS

This technique has identified navigation inaccuracy and led to repeat cross-sectional imaging. No screws have been misplaced in the senior author's cases since adopting this technique, and there have been no complications attributable to the technique.

CONCLUSION

Navigation inaccuracy is an inherent risk in MISS, but the described technique may mitigate this risk by providing a stable reference point.

Developing consensus for the management of pediatric cervical spine disorders and stabilization: a modified Delphi study

OBJECTIVE

Cervical spine disorders in children are relatively uncommon; therefore, paradigms for surgical and nonsurgical clinical management are not well established. The purpose of this study was to bring together an international, multidisciplinary group of pediatric cervical spine experts to build consensus via a modified Delphi approach regarding the clinical management of children with cervical spine disorders and those undergoing cervical spine stabilization surgery.

METHODS

A modified Delphi method was used to identify consensus statements for the management of children with cervical spine disorders requiring stabilization. A survey of current practices, supplemented by a literature review, was electronically distributed to 17 neurosurgeons and orthopedic surgeons experienced with the clinical management of pediatric cervical spine disorders. Subsequently, 52 summary statements were formulated and distributed to the group. Statements that reached near consensus or that were of particular interest were then discussed during an in-person meeting to attain further consensus. Consensus was defined as ≥ 80% agreement on a 4-point Likert scale (strongly agree, agree, disagree, strongly disagree).

RESULTS

Forty-five consensus-driven statements were identified, with all participants willing to incorporate them into their practice. For children with cervical spine disorders and/or stabilization, consensus statements were divided into the following categories: A) preoperative planning (12 statements); B) radiographic thresholds of instability (4); C) intraoperative/perioperative management (15); D) postoperative care (11); and E) nonoperative management (3). Several important statements reaching consensus included the following recommendations: 1) to obtain pre-positioning baseline signals with intraoperative neuromonitoring; 2) to use rigid instrumentation when technically feasible; 3) to provide postoperative external immobilization for 6-12 weeks with a rigid cervical collar rather than halo vest immobilization; and 4) to continue clinical postoperative follow-up at least until anatomical cervical spine maturity was reached. In addition, preoperative radiographic thresholds for instability that reached consensus included the following: 1) translational motion ≥ 5 mm at C1-2 (excluding patients with Down syndrome) or ≥ 4 mm in the subaxial spine; 2) dynamic angulation in the subaxial spine ≥ 10°; and 3) abnormal motion and T2 signal change on MRI seen at the same level.

CONCLUSIONS

In this study, the authors have demonstrated that a multidisciplinary, international group of pediatric cervical spine experts was able to reach consensus on 45 statements regarding the management of pediatric cervical spine disorders and stabilization. Further study is required to determine if implementation of these practices can lead to reduced complications and improved outcomes for children.

Navigation accuracy and assessability of carbon fiber-reinforced PEEK instrumentation with multimodal intraoperative imaging in spinal oncology

Radiolucent carbon-fiber reinforced PEEK (CFRP) implants have helped improve oncological follow-up and radiation therapy. Here, we investigated the performance of 3D intraoperative imaging and navigation systems for instrumentation and precision assessment of CFRP pedicle screws across the thoraco-lumbar spine. Thirty-three patients with spinal tumors underwent navigated CFRP instrumentation with intraoperative CT (iCT), robotic cone-beam CT (rCBCT) or cone-beam CT (CBCT) imaging. Two different navigation systems were used for iCT-/rCBCT- and CBCT-based navigation. Demographic, clinical and outcome data was assessed. Four blinded observers rated image quality, assessability and accuracy of CFRP pedicle screws. Inter-observer reliability was determined with Fleiss` Kappa analysis. Between 2018 and 2021, 243 CFRP screws were implanted (iCT:93, rCBCT: 99, CBCT: 51), of which 13 were non-assessable (iCT: 1, rCBCT: 9, CBCT: 3; *p = 0.0475; iCT vs. rCBCT). Navigation accuracy was highest using iCT (74%), followed by rCBCT (69%) and CBCT (49%) (*p = 0.0064; iCT vs. CBCT and rCBCT vs. CBCT). All observers rated iCT image quality higher than rCBCT/CBCT image quality (*p < 0.01) but relevant pedicle breaches were reliably identified with substantial agreement between all observers regardless of the imaging modality. Navigation accuracy for CFRP pedicle screws was considerably lower than expected from reports on titanium implants and CT may be best for reliable assessment of CFRP materials.

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.

Comparison of Radiation Exposure Between Anterior, Lateral, and Posterior Interbody Fusion Techniques and the Influence of Patient and Procedural Factors

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

The aim of this study was to elucidate the relative influence of multiple factors on radiation usage for anterior, lateral, and posterior based lumbar interbody fusion techniques.

SUMMARY OF BACKGROUND DATA

There has been substantial global growth in the performance of lumbar interbody fusions, due to evolution of techniques and approaches and increased attention to sagittal alignment. Utilization of intraoperative imaging guidance has similarly expanded, with a predominance of fluoroscopy and consequent increased radiation exposure. There have been no larger-scale studies examining the role of patient and procedural factors in driving radiation exposure across different interbody techniques.

METHODS

We used a clinical registry to review all single-level lumbar interbody fusions performed between January 2016 and October 2020. Operative records were reviewed for the amount of radiation exposure during the procedure. Patient age, biologic sex, body mass index (BMI), operative surgeon, surgical level, surgical time, and fusion technique were recorded. Multivariable adjusted analyses using negative binomial regression were used to account for confounding.

RESULTS

We included 134 interbody fusions; 80 performed with a posterior approach (TLIF/PLIF), 43 via an anterior approach (ALIF) with posterior pedicle fixation, and 9 performed with a lateral approach (LLIF/XLIF). Average radiation per case was 136.4 mGy (SE 17.3) for ALIF, 108.6 mGy (16.9) for LLIF/XLIF, and 60.5 mGy (7.4) for TLIF/PLIF. We identified lateral approaches, increased BMI, minimally invasive techniques, and more caudal operative levels as significantly associated with increased radiation exposure.

CONCLUSION

We identified several novel drivers of radiation exposure during interbody fusion procedures, including the relative importance of technique and the level at which the fusion is performed. More caudal levels of intervention and lateral based techniques had significantly greater radiation exposure.Level of Evidence: 4.

Hidden Error in Optical Stereotactic Navigation Systems and Strategy to Maximize Accuracy

BACKGROUND

Optical neuronavigation has been established as a reliable and effective adjunct to many neurosurgical procedures. Operations such as asleep deep brain stimulation (aDBS) benefit from the potential increase in accuracy that these systems offer. Built into these technologies is a degree of tolerated error that may exceed the presumed accuracy resulting in suboptimal outcomes.

OBJECTIVE

The objective of this study was to identify an underlying source of error in neuronavigation and determine strategies to maximize accuracy.

METHODS

A Medtronic Stealth system (Stealth Station 7 hardware, S8 software, version 3.1.1) was used to simulate an aDBS procedure with the Medtronic Nexframe system. Multiple configurations and orientations of the Nexframe-Nexprobe system components were examined to determine potential sources of, and to quantify navigational error, in the optical navigation system. Virtual entry point and target variations were recorded and analyzed. Finally, off-plan error was recorded with the AxiEM system and visual observation on a phantom head.

RESULTS

The most significant source of error was found to be the orientation of the reference marker plate configurations to the camera system, with the presentation of the markers perpendicular to the camera line of site being the most accurate position. Entry point errors ranged between 0.134 ± 0.048 and 1.271 ± 0.0986 mm in a complex, reproducible pattern dependent on the orientation of the Nexprobe reference plate. Target errors ranged between 0.311 ± 0.094 and 2.159 ± 0.190 mm with a similarly complex, repeatable pattern. Representative configurations were tested for physical error at target with errors ranging from 1.2 mm to 1.4 mm. Throughout data acquisition, no orientation was indicated as outside the acceptable tolerance by the Stealth software.

CONCLUSIONS

Use of optical neuronavigation is expected to increase in frequency and variety of indications. Successful implementation of this technology depends on understanding the tolerances built into the system. In situations that depend on extremely high precision, surgeons should familiarize themselves with potential sources of error so that systems may be optimized beyond the manufacturer's built-in tolerances. We recommend that surgeons align the navigation reference plate and any optical instrument's reference plate spheres in the plane perpendicular to the line of site of the camera to maximize accuracy.

Intraoperative image guidance for cervical spine surgery

Intraoperative image-guidance in spinal surgery has been influenced by various technological developments in imaging science since the early 1990s. The technology has evolved from simple fluoroscopic-based guidance to state-of-art intraoperative computed tomography (iCT)-based navigation systems. Although the intraoperative navigation is more commonly used in thoracolumbar spine surgery, this newer imaging platform has rapidly gained popularity in cervical approaches. The purpose of this manuscript is to address the applications of advanced image-guidance in cervical spine surgery and to describe the use of intraoperative neuro-navigation in surgical planning and execution. In this review, we aim to cover the following surgical techniques: anterior cervical approaches, atlanto-axial fixation, subaxial instrumentation, percutaneous interfacet cage implantation as well as minimally invasive posterior cervical foraminotomy (PCF) and unilateral laminotomy for bilateral decompression. The currently available data suggested that the use of 3D navigation significantly reduces the screw malposition, operative time, mean blood loss, radiation exposure, and complication rates in comparison to the conventional fluoroscopic-guidance. With the advancements in technology and surgical techniques, 3D navigation has potential to replace conventional fluoroscopy completely.

Device profile of the XVision-spine (XVS) augmented-reality surgical navigation system: overview of its safety and efficacy

Introduction: The field of augmented reality mediated spine surgery is growing rapidly and holds great promise for improving surgical capabilities and patient outcomes. Augmented reality can assist with complex or atypical cases involving challenging anatomy. As neuronavigation evolves, fundamental technical limitations remain in line-of-sight interruption and operator attention shift, which this novel augmented reality technology helps to address.Areas covered: XVision is a recently FDA-approved head mounted display for intraoperative neuronavigation, compatible with all current conventional pedicle screw technology. The device is a wireless, customizable headset with an integrated surgical tracking system and transparent retinal display. This review discusses the available literature on the safety and efficacy of XVision, as well as the current state of augmented reality technology in spine surgery.Expert opinion: Augmented-reality spine surgery is an emerging technology that may increase precision, efficiency, and safety as well as decrease radiation exposure of manual and robotic computer-navigated pedicle screw insertion techniques. The initial clinical experience with XVision has shown good outcomes and it has received positive operator feedback. Now that initial clinical safety and efficacy has been demonstrated, ongoing experience must be studied to empirically validate this technology and generate further innovation in this rapidly evolving field.

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.

Recent Trends, Technical Concepts and Components of Computer-Assisted Orthopedic Surgery Systems: A Comprehensive Review

Computer-assisted orthopedic surgery (CAOS) systems have become one of the most important and challenging types of system in clinical orthopedics, as they enable precise treatment of musculoskeletal diseases, employing modern clinical navigation systems and surgical tools. This paper brings a comprehensive review of recent trends and possibilities of CAOS systems. There are three types of the surgical planning systems, including: systems based on the volumetric images (computer tomography (CT), magnetic resonance imaging (MRI) or ultrasound images), further systems utilize either 2D or 3D fluoroscopic images, and the last one utilizes the kinetic information about the joints and morphological information about the target bones. This complex review is focused on three fundamental aspects of CAOS systems: their essential components, types of CAOS systems, and mechanical tools used in CAOS systems. In this review, we also outline the possibilities for using ultrasound computer-assisted orthopedic surgery (UCAOS) systems as an alternative to conventionally used CAOS systems.

The Feasibility of Long-Segment Fluoroscopy-guided Percutaneous Thoracic Spine Pedicle Screw Fixation, and the Outcome at Two-year Follow-up

Introduction: Posterior percutaneous instrumentation may represent a challenge when multiple levels need to be instrumentated, especially when including the upper thoracic spine. The aim of the present study was to evaluate the technical feasibility and the long-term outcome of such long constructs in different surgical conditions.

Materials and Methods: This investigation was a retrospective cohort study which included patients who underwent thoraco-lumbar percutaneous fixations. We collected clinical, surgical and radiological data, with a minimum follow-up of 24 months. Health-related quality-of-life, residual pain, instrumentation placement, and complications were studied.

Results: A total of 18 procedures were enrolled, in which 182 screws were implanted, (170 positioned in thoracic and 12 in lumbar pedicles, respectively). No surgical complications or hardware failure occurred in our series, 6 out of 182 (3,2%) screws had a partial pedicle breach, without neurological impairment or need for surgical revision.

Conclusion: According to our results, a fully posterior percutaneous approach for long thoraco-lumbar spine instrumentation can be considered safe and reproducible, although an adequate training is strictly required.

Machine learning for automated 3-dimensional segmentation of the spine and suggested placement of pedicle screws based on intraoperative cone-beam computer tomography

OBJECTIVE

The goal of this study was to develop and validate a system for automatic segmentation of the spine, pedicle identification, and screw path suggestion for use with an intraoperative 3D surgical navigation system.

METHODS

Cone-beam CT (CBCT) images of the spines of 21 cadavers were obtained. An automated model-based approach was used for segmentation. Using machine learning methodology, the algorithm was trained and validated on the image data sets. For measuring accuracy, surface area errors of the automatic segmentation were compared to the manually outlined reference surface on CBCT. To further test both technical and clinical accuracy, the algorithm was applied to a set of 20 clinical cases. The authors evaluated the system's accuracy in pedicle identification by measuring the distance between the user-defined midpoint of each pedicle and the automatically segmented midpoint. Finally, 2 independent surgeons performed a qualitative evaluation of the segmentation to judge whether it was adequate to guide surgical navigation and whether it would have resulted in a clinically acceptable pedicle screw placement.

RESULTS

The clinically relevant pedicle identification and automatic pedicle screw planning accuracy was 86.1%. By excluding patients with severe spinal deformities (i.e., Cobb angle > 75° and severe spinal degeneration) and previous surgeries, a success rate of 95.4% was achieved. The mean time (± SD) for automatic segmentation and screw planning in 5 vertebrae was 11 ± 4 seconds.

CONCLUSIONS

The technology investigated has the potential to aid surgeons in navigational planning and improve surgical navigation workflow while maintaining patient safety.

The optimal surgical techniques for pituitary tumors

In this paper, the currently used and well evaluated techniques for the surgery of pituitary tumors will be reviewed. Since the first surgical approaches to pituitary tumors more than 100 years have elapsed. Various surgical techniques have been developed, refined and standardized. Most of these tumors are to date treated via transsphenoidal approaches. Many pituitary adenomas, particularly, smaller, enclosed ones, can be completely excised and a selective adenomectomy is usually attempted. It leads to remission of hormonal oversecretion and also to recovery of pituitary function in many patients. The resection of pseudocapsule around the adenoma seems to improve the operative results further. Transcranial approaches, employing craniotomies, are still needed in some patients with pituitary adenomas and in many of those harbouring craniopharyngiomas. The operative techniques will be described and briefly commented. Moreover, the application and usefulness of several technical developments will be reviewed, such as the use of the endoscope, magnetic resonance imaging, fluorenscent dyes and neuronavigation. The use of the intraoperative Doppler probe, ultrasound and the value of intraoperative hormonal measurements will be briefly discussed. There is sufficient evidence that the best and optimal outcome in terms of tumor resection and correction of hormonal oversecretion as well as the lowest rate of complications are obtained in centers of excellence with sufficiently experienced, specialized surgeons and a high patient load.

A small 3D-printing model of macroadenomas for endoscopic endonasal surgery

PURPOSE

This paper examines the application of 3D printing technology in the endoscopic endonasal approach for the treatment of macroadenomas.

METHODS

We have retrospectively analysed 20 patients who diagnosed with macroadenoma underwent endoscopic transsphenoidal surgery in Wuhan Union hospital from January 2017 to May 2017. Among the 20 patients, 10 patients received the service of 3D printing technology preoperatively. The data of 3D processing and clinical result were recorded for further evaluation.

RESULTS

The 10 patients who received the service had a successful 3D printed model of their tumors, it shows the anatomy of sphenoid sinus, tumor location which were in good agreement with our intraoperative observations. The 10 patients who received the service had a less operation time (127.0 ± 15.53 vs. 143.40 ± 17.89), blood loss (159.90 ± 12.31 vs. 170.00 ± 29.06) and less postoperative complication rate (20% vs. 40%). the design time of the 3D images varies 2 h 10 min to 4 h 32 min. the printing time of the 3D models varies 10 h 12 min to 22 h 34 min.

CONCLUSIONS

The use of 3D printing technology has unquestionable potential applications to endoscopic endonasal approach for macroadenomas, in particular reflecting the complicated anatomy of sphenoid sinus and tumor location. Owing to the advantages of 3D printing technology, it may help the patients get a good prognosis.

Evidence Based Medicine Review of Posterior Thoracolumbar Minimally Invasive Technology

Background

Evaluate the current evidence in meta-analyses on posterior thoracolumbar minimally invasive surgery techniques and outcomes for degenerative conditions.

Methods

A systematic review of the literature from 1950 to 2015.

Results

The review of the literature yielded 34 meta-analysis studies evaluating posterior thoracolumbar minimally invasive techniques and outcomes for degenerative conditions. There were 11 studies included which investigated minimally invasive surgery (MIS) versus open posterior lumbar decompressions. There were 14 studies included which investigated MIS versus open posterior lumbar interbody fusions. Finally, there were 9 studies focused on navigation techniques and radiation safety within MIS procedures.

Conclusions

There are 34 meta-analysis studies evaluating minimally invasive to open thoracolumbar surgery for degenerative disease. The studies show a trend toward decreased estimated blood loss, decreased length of stay, decreased complications, similar fusion rates, improved accuracy, and decreased radiation when minimally invasive techniques are used.

Surgeon's and patient's radiation exposure during percutaneous thoraco-lumbar pedicle screw fixation: A prospective multicenter study of 100 cases

HYPOTHESIS

Percutaneous pedicle screw fixations (PPSF) are increasingly used in spine surgery, minimizing morbidity through less muscle breakdown but at the cost of intraoperative fluoroscopic guidance that generates high radiation exposure. Few studies have been conducted to measure them accurately.

MATERIAL AND METHODS

The objective of our study is to quantify, during a PPSF carried out in different experimented centers respecting current radiation protection recommendations, this irradiation at the level of the surgeon and the patient. We have prospectively included 100 FPVP procedures for which we have collected radiation doses from the main operator. For each procedure, the doses of whole-body radiation, lens and extremities were measured.

RESULTS

Our results show a mean whole body, extremity and lens exposure dose per procedure reaching 1.7±2.8μSv, 204.7±260.9μSv and 30.5±25.9μSv, respectively. According to these values, the exposure of the surgeon's extremities and lens will exceed the annual limit allowed by the International Commission on Radiological Protection (ICRP) after 2440 and 4840 procedures respectively.

CONCLUSION

Recent European guidelines will reduce the maximum annual exposure dose from 150 to 20mSv. The number of surgical procedures to not reach the eye threshold, according to our results, should not exceed 645 procedures per year. Pending the democratization of neuronavigation systems, the use of conventional fluoroscopy exposes the eyes in the first place. Therefore they must be protected by leaded glasses.

LEVEL OF PROOF

IV, case series.

Reduced Radiation Exposure and Puncture Time of Percutaneous Transpedicular Puncture with Real-Time Ultrasound Volume Navigation

OBJECTIVES

The present study introduced ultrasound volume navigation (UVN) to reduce the radiation exposure and puncture time of percutaneous transpedicular puncture in percutaneous vertebroplasty (PVP) or percutaneous kyphoplasty (PKP).

METHODS

We retrospectively reviewed the medical records of patients with osteoporotic vertebral compression fracture who had undergone PVP or PKP guided by UVN or fluoroscopy from September 2017 to December 2017.

RESULTS

We enrolled 10 patients (6 women, 4 men) with 24 pedicles involved in the present study. Significant reductions in fluoroscopy frequency (2.58 vs. 17.42; P < 0.01), exposure time (2.36 vs. 15.69 seconds; P < 0.01), and puncture time (4.13 vs. 19.21 minutes; P < 0.01) for each pedicle were observed in the UVN group compared with the fluoroscopy group. Obvious correlations among fluoroscopy frequency, exposure time, and puncture time for each pedicle were observed (P < 0.01). The visual analog scale scores and Oswestry Disability Index were both significantly improved after the procedures. All patients achieved excellent or good clinical outcomes. No complications were observed in any patient.

CONCLUSIONS

UVN could obviously reduce the radiation exposure and puncture time of percutaneous transpedicular puncture in PVP and PKP.

Bowel injury in lumbar spine surgery: a review of the literature

Although rarely documented in the medical literature, bowel perforation injury can be a severe complication of spine surgery. Our goal was to review current literature regarding this complication and study possible methods of avoidance. We conducted a literature search in the PubMed database between January 1960 and March 2016 using the terms abrasion, bowels, bowel, complication, injury, intestine, intra-abdominal sepsis/shock, perforation, lumbar, spine, surgery, visceral. Diagnostic criteria, outcomes, risk factors, surgical approach, and treatment strategy were the parameters extracted from the search results and used for review. Thirty-one patients with bowel injury were recognized in the literature. Bowel injury was more frequent in patients who underwent lumbar discectomy and microdiscectomy (18 of 31 patients, 58.1%). Minimally invasive surgery and lateral techniques involving fusions accounted for 10 of the reported cases (32.3%). Finally, 2 cases (6.5%) were reported in conjunction with sacrectomies and 1 case (3.2%) with posterior fusion plus anterior longitudinal ligament (ALL) release. Diagnosis was made mostly by clinical signs/symptoms of acute abdominal pain, post-surgical wound infection, and abscess or enterocutaneous fistulas. Significant risk factors for postoperative bowel injury were complex surgical anatomy, medical history of previous abdominal surgeries or infections, irradiation before surgery, errors related to surgical technique, lack of surgical experience, and instrumentation failure. The overall mortality rate from bowel injury was 12.9% (4 of 31 patients). The overall morbidity rate was 87.1% (27 of 31 patients). According to our review of the literature, bowel injury is linked to significant morbidity and mortality. It can be prevented with meticulous pre-surgical planning. When it occurs, timely treatment reduces the risks of morbidity and mortality.

Percutaneous screw placement in the lumbar spine with a modified guidance technique based on 3D CT navigation system

Several guidance techniques have been employed to increase accuracy and reduce surgical time during percutaneous placement of pedicle screws (PS). The purpose of our study was to present a modified technique for percutaneous placement of lumbar PS that reduces surgical time. We reviewed 23 cases of percutaneous PS placement using our technique for minimally invasive lumbar surgeries and 24 control cases where lumbar PS placement was done via common technique using Jamshidi needles (Becton, Dickinson and Company, Franklin Lakes, NJ, USA). An integrated computer-guided navigation system was used in all cases. In the technique modification, a handheld drill with a navigated guide was used to create the path for inserting guidewires through the pedicles and into the vertebral bodies. After drill removal, placement of the guidewires through the pedicles took place. The PS were implanted over the guidewires, through the pedicles and into the vertebral bodies. Intraoperative computed tomography was performed after screw placement to ensure optimal positioning in all cases. There were no intraoperative complications with either technique. PS placement was correct in all cases. The average time for each PS placement was 6.9 minutes for the modified technique and 9.2 minutes for the common technique. There was no significant difference in blood loss. In conclusion, this modified technique is efficient and contributes to reduced operative time.

Radiation reduction of minimally invasive transforaminal lumbar interbody fusion with localisation system in overweight patients: practical technique

AIMS

Minimally invasive transforaminal lumbar interbody fusion (MITLIF) has been well validated in overweight and obese patients who are consequently subject to a higher radiation exposure. This prospective multicentre study aimed to investigate the efficacy of a novel lumbar localisation system for MITLIF in overweight patients.

PATIENTS AND METHODS

The initial study group consisted of 175 patients. After excluding 49 patients for various reasons, 126 patients were divided into two groups. Those in Group A were treated using the localisation system while those in Group B were treated by conventional means. The primary outcomes were the effective radiation dosage to the surgeon and the exposure time.

RESULTS

There were 62 patients in Group A and 64 in Group B. The mean effective dosage was 0.0217 mSv (standard deviation (sd) 0.0079) in Group A and 0.0383 mSv (sd 0.0104) in Group B (p < 0.001). The mean fluoroscopy exposure time was 26.42 seconds (sd 5.91) in Group A and 40.67 seconds (sd 8.18) in Group B (p < 0.001). The operating time was 175.56 minutes (sd 32.23) and 206.08 minutes (sd 30.15) (p < 0.001), respectively. The mean pre-operative localisation time was 4.73 minutes (sd 0.84) in Group A and 7.03 minutes (sd 1.51) in Group B (p < 0.001). The mean screw placement time was 47.37 minutes (sd 10.43) in Group A and 67.86 minutes (sd 14.15) in Group B (p < 0.001). The pedicle screw violation rate was 0.35% (one out of 283) in Group A and 2.79% (eight out of 287) in Group B (p = 0.020).

CONCLUSION

The study shows that the localisation system can effectively reduce radiation exposure, exposure time, operating time, pre-operative localisation time, and screw placement time in overweight patients undergoing MITLIF. Cite this article: Bone Joint J 2017;99-B:944-50.

Significant reduction of fluoroscopy repetition with lumbar localization system in minimally invasive spine surgery: A prospective study

The conventional location methods for minimally invasive spinal surgery (MISS) were mainly based on repeated fluoroscopy in a trial-and-error manner preoperatively and intraoperatively. Localization system mainly consisted of preoperative applied radiopaque frame and intraoperative guiding device, which has the potential to minimize fluoroscopy repetition in MISS. The study aimed to evaluate the efficacy of a novel lumbar localization system in reducing radiation exposure to patients.Included patients underwent minimally invasive transforaminal lumbar interbody fusion (MISTLIF) or percutaneous transforaminal endoscopic discectomy (PTED). Patients treated with novel localization system were regarded as Group A, and patients treated without novel localization system were regarded as Group B.For PTED, The estimated effective dose was 0.41 ± 0.13 mSv in Group A and 0.57 ± 0.14 mSv in Group B (P < .001); the fluoroscopy exposure time of PTED was 22.18 ± 7.30 seconds in Group A and 30.53 ± 7.56 seconds in Group B (P < .001); The estimated cancer risk of radiation exposure was 22.68 ± 7.38 (10) in Group A and 31.20 ± 7.96 (10) in Group B (P < .001). For MISTLIF, the estimated effective dose was 0.45 ± 0.09 mSv in Group A and 0.58 ± 0.09 mSv in Group B (P < .001); The fluoroscopy exposure time was 25.41 ± 5.52 seconds in Group A and 32.82 ± 5.03 seconds in Group B (P < .001); The estimated cancer risk was 24.90 ± 5.15 (10) in Group A and 31.96 ± 5.04 (10) in Group B (P < .001). There were also significant differences in localization time and operation time between the 2 groups either for MISTLIF or PTED.The lumbar localization system could be a potential protection strategy for minimizing radiation hazards.

Minimally invasive scoliosis surgery assisted by O-arm navigation for Lenke Type 5C adolescent idiopathic scoliosis: a comparison with standard open approach spinal instrumentation

OBJECTIVE Recently, minimally invasive scoliosis surgery (MISS) was introduced for the correction of adult scoliosis. Multiple benefits including a good deformity correction rate and fewer complications have been demonstrated. However, few studies have reported on the use of MISS for the management of adolescent idiopathic scoliosis (AIS). The purpose of this study was to investigate the outcome of posterior MISS assisted by O-arm navigation for the correction of Lenke Type 5C AIS. METHODS The authors searched a database for all patients with AIS who had been treated with either MISS or PSF between November 2012 and January 2014. Levels of fusion, density of implants, operation time, and estimated blood loss (EBL) were recorded. Coronal and sagittal parameters were evaluated before surgery, immediately after surgery, and at the last follow-up. The accuracy of pedicle screw placement was assessed according to postoperative axial CT images in both groups. The 22-item Scoliosis Research Society questionnaire (SRS-22) results and complications were collected during follow-up. RESULTS The authors retrospectively reviewed the records of 45 patients with Lenke Type 5C AIS, 15 who underwent posterior MISS under O-arm navigation and 30 who underwent posterior spinal fusion (PSF). The 2 treatment groups were matched in terms of baseline characteristics. Comparison of radiographic parameters revealed no obvious difference between the 2 groups immediately after surgery or at the final follow-up; however, the MISS patients had significantly less EBL (p < 0.001) and longer operation times (p = 0.002). The evaluation of pain and self-image using the SRS-22 showed significantly higher scores in the MISS group (p = 0.013 and 0.046, respectively) than in the PSF group. Postoperative CT showed high accuracy in pedicle placement in both groups. No deep wound infection, pseudarthrosis, additional surgery, implant failure, or neurological complications were recorded in either group. CONCLUSIONS Minimally invasive scoliosis surgery is an effective and safe alternative to open surgery for patients with Lenke Type 5C AIS. Compared with results of the open approach, the outcomes of MISS are promising, with reduced morbidity. Before the routine use of MISS, however, long-term data are needed.

Performance evaluation of MIND demons deformable registration of MR and CT images in spinal interventions

Accurate intraoperative localization of target anatomy and adjacent nervous and vascular tissue is essential to safe, effective surgery, and multimodality deformable registration can be used to identify such anatomy by fusing preoperative CT or MR images with intraoperative images. A deformable image registration method has been developed to estimate viscoelastic diffeomorphisms between preoperative MR and intraoperative CT using modality-independent neighborhood descriptors (MIND) and a Huber metric for robust registration. The method, called MIND Demons, optimizes a constrained symmetric energy functional incorporating priors on smoothness, geodesics, and invertibility by alternating between Gauss-Newton optimization and Tikhonov regularization in a multiresolution scheme. Registration performance was evaluated for the MIND Demons method with a symmetric energy formulation in comparison to an asymmetric form, and sensitivity to anisotropic MR voxel-size was analyzed in phantom experiments emulating image-guided spine-surgery in comparison to a free-form deformation (FFD) method using local mutual information (LMI). Performance was validated in a clinical study involving 15 patients undergoing intervention of the cervical, thoracic, and lumbar spine. The target registration error (TRE) for the symmetric MIND Demons formulation (1.3  ±  0.8 mm (median  ±  interquartile)) outperformed the asymmetric form (3.6  ±  4.4 mm). The method demonstrated fairly minor sensitivity to anisotropic MR voxel size, with median TRE ranging 1.3-2.9 mm for MR slice thickness ranging 0.9-9.9 mm, compared to TRE  =  3.2-4.1 mm for LMI FFD over the same range. Evaluation in clinical data demonstrated sub-voxel TRE (<2 mm) in all fifteen cases with realistic deformations that preserved topology with sub-voxel invertibility (0.001 mm) and positive-determinant spatial Jacobians. The approach therefore appears robust against realistic anisotropic resolution characteristics in MR and yields registration accuracy suitable to application in image-guided spine-surgery.

Three-dimensional Fluoroscopy-based Navigation for the Pedicle Screw Placement in Patients with Primary Invasive Spinal Tumors

Background:

Although pedicle screw placement (PSP) is a well-established technique for spine surgery, the treatment of patients with primary invasive spinal tumor (PIST) has high surgical risks secondary to destroyed pedicles. Intraoperative three-dimensional fluoroscopy-based navigation (ITFN) system permits safe and accurate instrumentation of the spine with the advantage of obtaining intraoperative real-time three-dimensional images and automatic registration. The aim of this study is to evaluate the feasibility and accuracy of PSP using ITFN system for patients afflicted with PIST in the thoracic spine.

Methods:

Fifty-one patients diagnosed with PISTs were retrospectively analyzed, and 157 pedicles screws were implanted in 23 patients using the free-hand technique (free-hand group) and 197 pedicle screws were implanted in 28 patients using the ITFN system (ITFN group). Modified classification of Gertzbein and Robbins was used to evaluate the accuracy of PSP, and McCormick classification was applied for assessment of neurological function. Demographic data and factors affecting accuracy of screw insertion were compared using independent t-test while comparison of accuracy of screw insertion between the two groups was analyzed with Chi-square test.

Results:

Of 51 patients, 39 demonstrated improved neurological status and the other 12 patients reported that symptoms remained the same. In the free-hand group, 145 screws (92.4%) were Grade I, 9 screws (5.7%) were Grade II, and 3 screws (1.9%) were Grade III. In the ITFN group, 192 screws (97.4%) were Grade I, 5 screws (2.6%) were Grade II, and no Grade III screw was detected. Statistical analysis showed that the accuracies of pedicle screws in the two groups are significantly different (χ² = 4.981, P = 0.026).

Conclusions:

The treatments of PISTs include total tumor resection and reconstruction of spine stability. The ITFN system provides a high accuracy of pedicle screw placement.

A Low-Cost, Passive Navigation Training System for Image-Guided Spinal Intervention

BACKGROUND

Navigation technology is used for training in various medical specialties, not least image-guided spinal interventions. Navigation practice is an important educational component that allows residents to understand how surgical instruments interact with complex anatomy and to learn basic surgical skills such as the tridimensional mental interpretation of bidimensional data. Inexpensive surgical simulators for spinal surgery, however, are lacking. We therefore designed a low-cost spinal surgery simulator (Spine MovDigSys 01) to allow 3-dimensional navigation via 2-dimensional images without altering or limiting the surgeon's natural movement.

METHODS

A training system was developed with an anatomical lumbar model and 2 webcams to passively digitize surgical instruments under MATLAB software control. A proof-of-concept recognition task (vertebral body cannulation) and a pilot test of the system with 12 neuro- and orthopedic surgeons were performed to obtain feedback on the system. Position, orientation, and kinematic variables were determined and the lateral, posteroanterior, and anteroposterior views obtained.

RESULTS

The system was tested with a proof-of-concept experimental task. Operator metrics including time of execution (t), intracorporeal length (d), insertion angle (α), average speed (v¯), and acceleration (a) were obtained accurately. These metrics were converted into assessment metrics such as smoothness of operation and linearity of insertion. Results from initial testing are shown and the system advantages and disadvantages described.

CONCLUSIONS

This low-cost spinal surgery training system digitized the position and orientation of the instruments and allowed image-guided navigation, the generation of metrics, and graphic recording of the instrumental route. Spine MovDigSys 01 is useful for development of basic, noninnate skills and allows the novice apprentice to quickly and economically move beyond the basics.

Cervical screw placement using rapid prototyping drill templates for navigation: a literature review

PURPOSE

Due to the high screw malposition rate and the potential risk of neurovascular injury in cervical fixation surgeries, guided tools, mainly computer-assisted surgery navigation systems and rapid prototyping drill templates (RPDTs) have increasingly been developed to help surgeons improve screw placement accuracy. Although RPDTs have been used in cervical surgeries for almost 2 decades, no specific review has been performed detailing the state of this technique. Thus, in the current review, we fully discuss the status of applying RPDTs in cervical surgeries.

METHODS

Studies that tested the accuracy and reliability of RPDTs in guiding cervical screw placements were included in this review. The fabrication workflow and usage of RPDTs, the accuracy and reliability of using RPDTs for screw and plate placement, the advantages and disadvantages of RPDTs and their prospects for future applications as a part of cervical fixation instrumentation are discussed.

RESULTS

As the design of RPDTs becomes more rational, the accuracy and reliability of these devices have significantly improved in cervical fixation surgeries. Moreover, RPDTs decrease the intraoperative radiation exposure for surgeons and patients relative to conventional methods. However, some disadvantages also exist. The fabrication of RPDTs is time-consuming, and the time required to learn the related software is long.

CONCLUSION

We believe that because of their merits, the RPDT technique is worth promoting for use in cervical surgeries. However, the time-consuming fabrication workflow and the long period required to learn the related software might limit its widespread use. In the future, the workflow should be simplified to reduce the extra workload for surgeons. Moreover, more clinical studies with high-level evidence are still needed to further test its accuracy and feasibility.

Novel Techniques in the Surgical Treatment of Acromegaly: Applications and Efficacy

Since the establishment of transsphenoidal microsurgery as the operative treatment of choice in most patients with acromegaly 40 years ago, a few novel technical developments have evolved. Their application, utility and efficacy will be briefly discussed in this review article, based on an analysis of published results and the authors' personal experience. The endoscope was additionally used to search for residual tumours in locations which could not be visualised with the operating microscope. In many centres it has by now fully replaced the operating microscope. Extended endoscopic operations hardly have limits in respect to accessible pathology. Overall, the results and complications reported from microsurgical and endoscopic series are comparable. Intraoperative magnetic resonance imaging allows depicting the completeness of a tumour resection. While in many patients additional tumour resections are performed on the basis of intraoperative imaging, the improvements in hormonal remission rates reported are less impressive. Neuronavigation uses imaging data to improve the surgeon's orientation, and it is certainly a major asset to the inexperienced. In high-caseload centres it is mainly appreciated in anatomical variants and reoperations. While the Doppler probe is a valuable and easily affordable gadget to avoid vascular arterial injury, intraoperative ultrasound imaging of tumour extension has a much poorer resolution than magnetic resonance imaging and is thus not widely implemented. The clinical value of intraoperative growth hormone measurements is controversially discussed. In summary, the application of modern technology has only led to a minor improvement of results, but it has widened the spectrum of accessible pathologies and increased the safety of the procedures for the patient. It is expected that outcomes will continue to improve as novel techniques and concepts are being developed.

Puncture Reduction in Percutaneous Transforaminal Endoscopic Discectomy with HE's Lumbar LOcation (HELLO) System: A Cadaver Study

BACKGROUND

Percutaneous transforaminal endoscopic discectomy (PTED) usually requires numerous punctures under X-ray fluoroscopy. Repeated puncture will lead to more radiation exposure and reduce the beginners' confidence.

OBJECTIVE

This cadaver study aimed to investigate the efficacy of HE's Lumbar Location (HELLO) system in puncture reduction of PTED.

STUDY DESIGN

Cadaver study.

SETTING

Comparative groups.

METHODS

HELLO system consists of self-made surface locator and puncture locator. One senior surgeon conducted the puncture procedure of PTED on the left side of 20 cadavers at L4/L5 and L5/S1 level with the assistance of HELLO system (Group A). Additionally, the senior surgeon conducted the puncture procedure of PTED on the right side of the cadavers at L4/L5 and L5/S1 level with traditional methods (Group B). On the other hand, an inexperienced surgeon conducted the puncture procedure of PTED on the left side of the cadavers at L4/L5 and L5/S1 level with the assistance of our HELLO system (Group C).

RESULTS

At L4/L5 level, there was significant difference in puncture times between Group A and Group B (P<0.001), but no significant difference was observed between Group A and Group C (P = 0.811). Similarly at L5/S1 level, there was significant difference in puncture times between Group A and Group B (P<0.001), but no significant difference was observed between Group A and Group C (P = 0.981). At L4/L5 level, there was significant difference in fluoroscopy time between Group A and Group B (P<0.001), but no significant difference was observed between Group A and Group C (P = 0.290). Similarly at L5/S1 level, there was significant difference in fluoroscopy time between Group A and Group B (P<0.001), but no significant difference was observed between Group A and Group C (P = 0.523). As for radiation exposure, HELLO system reduced 39%-45% radiation dosage when comparing Group A and Group B, but there was no significant difference in radiation exposure between Group A and Group C whatever at L4/L5 level or L5/S1 level (P>0.05). There was no difference in location time between Group A and Group B or Group A and Group C either at L4/L5 level or L5/S1 level (P>0.05).

LIMITATIONS

Small-sample preclinical study.

CONCLUSION

HELLO system was effective in reducing puncture times, fluoroscopy time and radiation exposure, as well as the difficulty of learning PTED. (2015-RES-127).

Significant Improvement of Puncture Accuracy and Fluoroscopy Reduction in Percutaneous Transforaminal Endoscopic Discectomy With Novel Lumbar Location System: Preliminary Report of Prospective Hello Study

Prospective nonrandomized control study.The study aimed to investigate the implication of the HE's Lumbar LOcation (HELLO) system in improving the puncture accuracy and reducing fluoroscopy in percutaneous transforaminal endoscopic discectomy (PTED).Percutaneous transforaminal endoscopic discectomy is one of the most popular minimally invasive spine surgeries that heavily depend on repeated fluoroscopy. Increased fluoroscopy will induce higher radiation exposure to surgeons and patients. Accurate puncture in PTED can be achieved by accurate preoperative location and definite trajectory.The HELLO system mainly consists of self-made surface locator and puncture-assisted device. The surface locator was used to identify the exact puncture target and the puncture-assisted device was used to optimize the puncture trajectory. Patients who had single L4/5 or L5/S1 lumbar intervertebral disc herniation and underwent PTED were included the study. Patients receiving the HELLO system were assigned in Group A, and those taking conventional method were assigned in Group B. Study primary endpoint was puncture times and fluoroscopic times, and the secondary endpoint was location time and operation time.A total of 62 patients who received PTED were included in this study. The average age was 45.35 ± 8.70 years in Group A and 46.61 ± 7.84 years in Group B (P = 0.552). There were no significant differences in gender, body mass index, conservative time, and surgical segment between the 2 groups (P > 0.05). The puncture times were 1.19 ± 0.48 in Group A and 6.03 ± 1.87 in Group B (P < 0.001). The fluoroscopic times were 14.03 ± 2.54 in Group A and 25.19 ± 4.28 in Group B (P < 0.001). The preoperative location time was 4.67 ± 1.41 minutes in Group A and 6.98 ± 0.94 minutes in Group B (P < 0.001). The operation time was 79.42 ± 10.15 minutes in Group A and 89.65 ± 14.06 minutes in Group B (P = 0.002). The hospital stay was 2.77 ± 0.95 days in Group A and 2.87 ± 1.02 days in Group B (P = 0.702). There were no significant differences in the complication rate between the 2 groups (P = 0.386).The highlight of HELLO system is accurate preoperative location and definite trajectory. This preliminary report indicated that the HELLO system significantly improves the puncture accuracy of PTED and reduces the fluoroscopic times, preoperative location time, as well as operation time. (ChiCTR-ICR-15006730).

Novel method for setting up 3D navigation system with skin-fixed dynamic reference frame in anterior cervical surgery

PURPOSE

To introduce easy and useful methods using 3D navigation system with skin-fixed dynamic reference frame (DRF) in anterior cervical surgery and to validate its accuracy.

METHODS

From September 2012 to May 2013, 31 patients underwent anterior cervical surgery and a total of 48 caspar distraction pins were inserted into each cervical vertebra. Every operation was performed using O-arm® navigation system with skin-fixed DRF. To validate the accuracy of these methods, a custom-made metal sleeve was used. In surgical field, through the metal sleeve, the tip of a navigation probe promptly contacts to the tip of caspar pin. We measured the vertical and horizontal distances and the angular deviation in sagittal plane between the caspar pin and the navigation probe on the virtual images and evaluated accuracy of navigation system with skin fixed DRF.

RESULTS

Total 31 (males 20, females 11) patients and 48 caspar pins were included in this study. The mean horizontal distance between the caspar pin and the navigation probe displayed in navigation monitor was 0.49 ± 0.71 mm. The mean vertical distance between the caspar pin and the navigation probe displayed in navigation monitor was 0.88 ± 0.93 mm. And the mean angular deviation in sagittal plane between the caspar pin and the navigation probe displayed in navigation monitor was 0.59 ± 0.55°.

CONCLUSIONS

3D navigation system with skin-fixed DRF in anterior cervical surgery is a simple and reliable method and it can be a helpful supplement to a spine surgeon's judgement.

The effect of lateral wall perforation on screw pull-out strength: a cadaveric study

BACKGROUND

Lateral pedicle wall perforations occur frequently during pedicle screw insertion. Although it is known that such an occurrence decreases the screw pull-out strength, the effect has not been quantified biomechanically.

MATERIALS AND METHODS

Twenty fresh cadaveric lumbar vertebrae were harvested, and the bone mineral density (BMD) of each was evaluated with dual-energy radiography absorptiometry (DEXA). Twenty matched, 6.5-mm pedicle screws were inserted in two different manners in two groups, the control group and the experimental group. In the control group, the pedicle screw was inserted in a standard fashion taking adequate precaution to ensure there was no perforation of the wall. In the experimental group, the pedicle screw was inserted such that its trajectory perforated the lateral wall. Group assignments were done randomly, and the maximal fixation strength was recorded for each screw pull-out test with a material-testing system (MTS 858 II).

RESULTS

The average BMD for both groups was 0.850 g/cm(2) (0.788-0.912 g/cm(2)). The average (and standard deviation) maximal pull-out forces were 1,015.8 ± 249.40 N for the experimental group and 1,326.0 ± 320.50 N for the control group. According to a paired t-test, the difference between the two groups was statistically significant (P < 0.001).

CONCLUSION

The results of this study confirm that the maximal pull-out strength of pedicle screws decreases by approximately 23.4% when the lateral wall is perforated.

Intraoperative navigation in minimally invasive transforaminal lumbar interbody fusion and lateral interbody fusion

Advances in spine surgery continue to provide increased safety and efficacy for a wide range of disorders. Minimally invasive techniques have revolutionized many of the ways spinal disorders are treated, offering optimal outcomes with minimal complications on the premise of avoiding unnecessary traumatic muscle dissection and disruption. Percutaneous spine surgery is mostly, if not purely, fluoroscopically based. Hence, there is an increased amount of radiation exposure to the patient, surgeons, and the operating-room team. To address this issue, navigation-based percutaneous techniques have evolved with the aim of reducing the radiation exposure while achieving all goals of minimally invasive spine surgery.

Novel placement of cortical bone trajectory screws in previously instrumented pedicles for adjacent-segment lumbar disease using CT image-guided navigation

OBJECT

Symptomatic adjacent-segment lumbar disease (ASLD) after lumbar fusion often requires subsequent surgical intervention. The authors report utilizing cortical bone trajectory (CBT) pedicle screw fixation with intraoperative CT (O-arm) image-guided navigation to stabilize spinal levels in patients with symptomatic ASLD. This unique technique results in the placement of 2 screws in the same pedicle (1 traditional pedicle trajectory and 1 CBT) and obviates the need to remove preexisting instrumentation.

METHODS

The records of 5 consecutive patients who underwent lumbar spinal fusion with CBT and posterior interbody grafting for ASLD were retrospectively reviewed. All patients underwent screw trajectory planning with the O-arm in conjunction with the StealthStation navigation system. Basic demographics, operative details, and radiographic and clinical outcomes were obtained.

RESULTS

The average patient age was 69.4 years (range 58-82 years). Four of the 5 surgeries were performed with the Minimal Access Spinal Technologies (MAST) Midline Lumbar Fusion (MIDLF) system. The average operative duration was 218 minutes (range 175-315 minutes). In the entire cohort, 5.5-mm cortical screws were placed in previously instrumented pedicles. The average hospital stay was 2.8 days (range 2-3 days) and there were no surgical complications. All patients had more than 6 months of radiographic and clinical follow-up (range 10-15 months). At last follow-up, all patients reported improved symptoms from their preoperative state. Radiographic follow-up showed Lenke fusion grades of A or B.

CONCLUSIONS

The authors present a novel fusion technique that uses CBT pedicle screw fixation in a previously instrumented pedicle with intraoperative O-arm guided navigation. This method obviates the need for hardware removal. This cohort of patients experienced good clinical results. Computed tomography navigation was critical for accurate CBT screw placement at levels where previous traditional pedicle screws were already placed for symptomatic ASLD.

The clinical experience of computed tomographic-guided navigation system in c1-2 spine instrumentation surgery

Objective

To identify the accuracy and efficiency of the computed tomographic (CT)-based navigation system on upper cervical instrumentation, particularly C1 lateral mass and C2 pedicle screw fixation compared to previous reports.

Methods

Between May 2005 and March 2014, 25 patients underwent upper cervical instrumentation via a CT-based navigation system. Seven patients were excluded, while 18 patients were involved. There were 13 males and five females; resulting in four degenerative cervical diseases and 14 trauma cases. A CT-based navigation system and lateral fluoroscopy were used during the screw instrumentation procedure. Among the 58 screws inserted as C1-2 screws fixation, their precise positions were evaluated by postoperative CT scans and classified into three categories : in-pedicle, non-critical breach, and critical breach.

Results

Postoperatively, the precise positions of the C1-2 screws fixation were 81.1% (47/58), and 8.6% (5/58) were of non-critical breach, while 10.3% (6/58) were of critical breach. Most (5/6, 83.3%) of the critical breaches and all of non-critical breaches were observed in the C2 pedicle screws and there was only one case of a critical breach among the C1 lateral mass screws. There were three complications (two vertebral artery occlusions and a deep wound infection), but no postoperative instrument-related neurological deteriorations were seen, even in the critical breach cases.

Conclusion

Although CT-based navigation systems can result in a more precise procedure, there are still some problems at the upper cervical spine levels, where the anatomy is highly variable. Even though there were no catastrophic complications, more experience are needed for safer procedure.

Neuronavigation in small animals: development, techniques, and applications

A persistent obstacle to accurate diagnosis and treatment of brain disease has been the difficulties in safely obtaining representative biopsy material in a live patient. Major problems are the variability in the anatomy between individuals and the inability to reliably locate deep structures through reliance on surface anatomic features. Although stereotaxic devices have been available for many years, they have now been supplanted by frameless systems, which are more accurate and less cumbersome and allow good surgical access and provision of intraoperative feedback of instrument location.