Improved accuracy of computer-assisted cervical pedicle screw insertion

Accuracy of Cervical Pedicle Screw Insertion With and Without a Navigation-Linked High-Speed Drill: A Retrospective Clinical Study

INTRODUCTION

Cervical pedicle screw (CPS) fixation provides high stability but poses a risk of nerve and vascular injury. Although useful for reducing CPS deviation rates, navigation systems cannot completely eliminate deviation. This study aimed to compare two methods for creating insertion paths, one using a navigation-linked high-speed drill (NAVI drill) and the other using conventional manual probing.

METHODS

Our study comprised 104 patients with 509 CPSs at the C3-6 level who were treated at our institution between 2017 and 2023. CPS deviations were graded according to the Neo classification system, and the deviation direction (medial, lateral, cranial, or caudal) was assessed. Complications associated with CPS deviation were also investigated. We compared cases that used the NAVI drill (Group M) with those that used manual probing (Group N).

RESULTS

Group M included 45 cases (252 screws), and Group N included 59 cases (257 screws). The CPS deviation rate was grade 1 or higher in 14.7% and 17.1% of cases in Groups M and N, respectively (p = 0.469). It was grade 2 or higher in 1.2% and 4.3% of cases in Groups M and N, respectively (p = 0.222). The medial, lateral, caudal, and cranial deviation direction rates were 56.8%, 2.7%, 40.5%, and 0% in Group M and 13.6%, 72.7%, 11.4%, and 2.3% in Group N, respectively (p < 0.001). In one case in Group N, a grade 3 lateral deviation resulted in vertebral artery injury (VAI).

CONCLUSIONS

The use of the NAVI drill was associated with a slightly lower, albeit insignificant, CPS deviation rate. However, it significantly lowered the proportion of lateral deviations. Therefore, the NAVI drill is a useful tool for preventing VAI.

Top 100 Most Cited Articles on Intraoperative Image-Guided Navigation in Spine Surgery

Navigation technologies have become essential in spine surgery over the last decade, offering precise procedures and minimizing risks. To the best of our knowledge, this is the first bibliometric analysis on this topic, providing insights and trends on topics, authors, and journals. The study identifies and analyzes the 100 most cited articles related to navigation in spine surgery. A systematic search was performed in Scopus and Google Scholar to identify all articles related to navigation in spine surgery (38,057 articles). The 100 most cited were analyzed for citations, titles, abstracts, authors, affiliations, keywords, country and institute of origin, year of publication, and level of evidence. The search was conducted in October 2023. The 100 most cited articles were published between 1995 and 2019, with 2010 to 2019 being the most prolific decade (46%). The most cited article had 733 citations, and the paper with the most citations per year averaged 59.27 citations/year. The Spine Journal had the most articles (34%). The United States contributed the most articles (39%). Most publications were clinical research and reviews (94%), with an overall evidence grade of IV-V (63%). A positive trend was noted in the last decade for incorporating augmented reality. This bibliometric analysis offers valuable insights and trends in spine surgery navigation literature. The findings indicate that technological advancements have led to more articles with higher levels of evidence. These pivotal articles shape evidence-based medicine, future surgeons, and industry improvements in navigated spine surgery.

Assessing the Accuracy and Safety Thresholds of Patient-Specific Screw Guide Template System in Cervical and Thoracic Spine Surgeries Using DAST Measurements

Introduction

To analyze the reliability of the newly developed patient-specific Screw Guide Template (SGT) system as an intraoperative navigation device for spinal screw insertion.

Methods

We attempted to place 428 screws for 51 patients. The accuracy of the screw track was assessed by deviation of the screw axis from the preplanned trajectory on postoperative CT. The safety of the screw insertion was evaluated by the bone breach of the screw. The bone diameter available for screw trajectory (DAST) was measured, and the relations to the bone breach were analyzed.

Results

In the inserted screws, 98.4% were defined as accurate, and 94.6% were contained in the target bone. In the cervical spine, the screw deviation between breaching (0.57 mm) and contained screws (0.43 mm) did not significantly differ, whereas DAST for breaching screws (3.62 mm) was significantly smaller than contained screws (5.33 mm) (p<0.001). Cervical screws with ≥4.0 mm DAST showed a significantly lower incidence of bone breach (0.4%) than ≤3.9 mm DAST (28.3%) (p<0.001). In the thoracic spine, screw deviation and DAST had significant differences between breaching (1.54 mm, 4.41 mm) and contained (0.75 mm, 6.07 mm) (p<0.001). The incidence of the breach was significantly lower in thoracic screws with ≥5.0 mm (1.9%) than ≤4.9 (21.9%) DAST (p<0.001).

Conclusions

This study demonstrated that our SGT system could support precise screw insertion for 98.4% accuracy and 94.6% safety. DAST was recommended to be ≥4.0 and ≥5.0 mm in the cervical and thoracic spines for safe screw insertion.

MakoTM robotic-arm-assisted total hip and total knee arthroplasty outcomes in an orthopedic oncology setting: A case series

Background

The MAKO Robotic-Arm system is a cutting-edge technology which combines both computed tomography (CT) scanning and three-dimensional planning to determine the ideal size and orientation of implants prior to bone resection. It is typically utilized within a general orthopedic setting for joint replacement procedures, such as total joint arthroplasties. However, its use within orthopedic oncology, which contains a much more compromised patient population and more complex surgical treatment, is not well documented within the literature.

Question/purposes

To determine the patient outcomes of those who underwent a total hip arthroplasty (THA) or total knee arthroplasty (TKA) at Morristown Medical Center using the MAKO Robotic-Arm System. Particularly, we aspired to delve into the use of the MAKO in an orthopedic oncology setting for patients with a degenerative hip or knee and a history of cancer or other orthopedic tumor, impending pathological fracture, PVNS, chondromatosis, radiation therapy, or other oncological related conditions.

Patients and methods

Our institution monitored twenty-five individuals with unique orthopedic oncology conditions that underwent MAKO robotic-assisted total hip and knee arthroplasty. This was performed between 2020 and 2022 at Morristown Medical Center in New Jersey. During this time period, 52% (13/25) of the operations were performed on knees and 48% (12/25) were performed on hips. Data regarding patient demographics, body mass index (BMI), medications, hemoglobin, hematocrit, comorbidities, American Society of Anesthesiologists (ASA) Class, operative data, the length of stay (LOS), readmission rates due to infection or periprosthetic fractures, and complications were collected retrospectively. All confidence intervals were calculated at the 95% confidence level.

Results

Postoperatively, the average LOS was 3.2 days, and there were no complications after any of the MAKO-assisted joint arthroplasty procedures. Additionally, there were no readmissions at any of our recorded intervals - 1-30, 1-60, 1-90, and 1 year - however one patient presented to the emergency department after falling 4 days post-operatively. X-ray imaging ultimately revealed no periprosthetic fracture or malalignment of the prosthesis.

Conclusions

The utilization of the MAKO Robotic-Arm System for joint arthroplasty procedures (THAs and TKAs) on orthopedic oncology patients yielded exceptional outcomes, with no complications or readmissions directly attributed to the use of this innovative robotic technology. Thus, this newly emerging surgical system holds great promise, potentially revolutionizing the approach for selected orthopedic oncology patients undergoing total joint arthroplasty compared to the traditional manual techniques. It further demonstrates that its use in an orthopedic oncology setting - where the cohort of patients are often compromised, leading to more intricate surgeries with heightened risks - elicits safety and provides optimal outcomes for patients. Nevertheless, its role within the field is evolving, and in the coming years, as it gains further popularity and sees broader application by orthopedic oncology surgeons, its potential will become clearer. To solidify its position, future clinical investigations and prospective research should be conducted to support the preference of the MAKO system over traditional manual techniques. This will help provide the necessary evidence to advocate for its widespread adoption and continued advancements in orthopedic oncology procedures.

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

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

Accuracy of the trough position in expansive open-door cervical laminoplasty using computer navigation techniques: a single-centre retrospective study

PURPOSE

This study aims to assess whether computer navigation can improve the accuracy of the trough position and clinical outcomes of expansive open-door cervical laminoplasty (EOLP).

METHODS

We reviewed a single centre of 28 conventional EOLP and 24 computer navigation EOLP cases. The conventional group had 102 laminae while the navigation group had 88. The distance from the medial cortex to the pedicle on the open-door side (OD) and hinge side (HD) was measured. Furthermore, the area of the spinal canal corresponding to each lamina before and after the surgical procedure was also measured. We then compared the differences in radiographic parameters and clinical outcomes between the two groups.

RESULTS

OD and HD were smaller in the navigation group compared to the conventional group, and the enlarged area of the spinal canal was larger in the navigation group than in the conventional group. The Japanese Orthopaedic Association (JOA) scores one year after the surgical procedure improved in both groups compared to the pre-operative period, and the JOA recovery rate was higher in the navigation group. The incidence of hinge fracture was lower in the navigation group, and the incidence of C5 palsy and axial pain was not statistically different between the two groups.

CONCLUSION

The use of computer navigation techniques has the potential to significantly improve the accuracy of EOLP compared to conventional procedures. It has been shown to more fully expand the spinal canal and contribute to clinical efficacy.

3D-printed guides for cervical pedicle screw placement in primary spine tumor: Case report and technical description

Introduction

For spine surgeons, dealing with unstable cervical spine has been usually challenging, and this becomes more difficult when facing a primary craniovertebral junction tumor. Primary spine tumor surgery should always include column reconstruction in order to guarantee biomechanical stability of the spine, but surgeons should always be aware that instrumentations could create interferences with postoperative radiations. However, although carbon fiber instrumentations have started to be used in thoracolumbar oncology for few years, these options are still not available for cervical spine. In the reported case, the adopted strategy to obtain adequate column reconstruction was based on the idea of reducing the amount of titanium needed for posterior fixation and maximizing the distance between the radiation target and titanium rods.

Case report and aim

We present the case of a 53-year-old woman harboring a craniovertebral junction chordoma. A short occipito-C3 construct was selected. Specifically, titanium cervical pedicle screws were placed by using a new technology consisting in patient-tailored and customized 3D-printed guides. The aim of this case report is to determine the feasibility and safety of 3D-printed guides for cervical pedicle screw (CPS) positioning, even in the case of cervical spine tumor.

Conclusion

CPS could represent a good solution by providing strong biomechanical purchase and tailored 3D-printed guides could increase the safety and the accuracy of this challenging screw placement, even in oncological patients.

Accuracy of pedicle screw placement using neuronavigation based on intraoperative 3D rotational fluoroscopy in the thoracic and lumbar spine

INTRODUCTION

In spinal surgery, precise instrumentation is essential. This study aims to evaluate the accuracy of navigated, O-arm-controlled screw positioning in thoracic and lumbar spine instabilities.

MATERIALS AND METHODS

Posterior instrumentation procedures between 2010 and 2015 were retrospectively analyzed. Pedicle screws were placed using 3D rotational fluoroscopy and neuronavigation. Accuracy of screw placement was assessed using a 6-grade scoring system. In addition, screw length was analyzed in relation to the vertebral body diameter. Intra- and postoperative revision rates were recorded.

RESULTS

Thoracic and lumbar spine surgery was performed in 285 patients. Of 1704 pedicle screws, 1621 (95.1%) showed excellent positioning in 3D rotational fluoroscopy imaging. The lateral rim of either pedicle or vertebral body was protruded in 25 (1.5%) and 28 screws (1.6%), while the midline of the vertebral body was crossed in 8 screws (0.5%). Furthermore, 11 screws each (0.6%) fulfilled the criteria of full lateral and medial displacement. The median relative screw length was 92.6%. Intraoperative revision resulted in excellent positioning in 58 of 71 screws. Follow-up surgery due to missed primary malposition had to be performed for two screws in the same patient. Postsurgical symptom relief was reported in 82.1% of patients, whereas neurological deterioration occurred in 8.9% of cases with neurological follow-up.

CONCLUSIONS

Combination of neuronavigation and 3D rotational fluoroscopy control ensures excellent accuracy in pedicle screw positioning. As misplaced screws can be detected reliably and revised intraoperatively, repeated surgery for screw malposition is rarely required.

Vital Role of In-House 3D Lab to Create Unprecedented Solutions for Challenges in Spinal Surgery, Practical Guidelines and Clinical Case Series

For decades, the advantages of rapid prototyping for clinical use have been recognized. However, demonstrations of potential solutions to treat spinal problems that cannot be solved otherwise are scarce. In this paper, we describe the development, regulatory process, and clinical application of two types of patient specific 3D-printed devices that were developed at an in-house 3D point-of-care facility. This 3D lab made it possible to elegantly treat patients with spinal problems that could not have been treated in a conventional manner. The first device, applied in three patients, is a printed nylon drill guide, with such accuracy that it can be used for insertion of cervical pedicle screws in very young children, which has been applied even in semi-acute settings. The other is a 3D-printed titanium spinal column prosthesis that was used to treat progressive and severe deformities due to lysis of the anterior column in three patients. The unique opportunity to control size, shape, and material characteristics allowed a relatively easy solution for these patients, who were developing paraplegia. In this paper, we discuss the pathway toward the design and final application, including technical file creation for dossier building and challenges within a point-of-care lab.

Accuracy of pedicle screw placement using patient-specific template guide system

BACKGROUND

Despite repeated efforts for accurate cervical pedicle screw insertion, malpositioning of the inserted screw is commonly noted. To avoid neurovascular complications during cervical pedicle screw insertion, we have developed a new patient-specific screw guide system. This study aimed to evaluate the accuracy of cervical PS placement using the new patient-specific screw guide system.

METHODS

This study is a retrospective clinical evaluation of prospectively enrolled patients. Seventeen consecutively enrolled patients who underwent posterior cervical fusion using the guide system were included. Firstly, three-dimensional planning of pedicle screw placement was done using simulation software. A screw guide for each vertebra was constructed preoperatively. A total of 77 screws were inserted with the guides. Postoperative computed tomography was used to evaluate pedicle perforation, and screw deviations, between the planned and actual screw positions, were measured.

RESULTS

A total of 76 screws (98.7%) were completely inside the pedicle (C3-7), without neurovascular injuries. The mean screw deviations from the planned trajectory at the narrowest point of the pedicle and at the entry point in the axial and sagittal planes were 0.56 ± 0.43 mm and 0.43 ± 0.35 mm and 0.43 ± 0.30 mm and 0.63 ± 0.50 mm, respectively. There were no significant differences in any parameter at different spinal levels. Angular deviations in the sagittal and axial planes were 2.94 ± 2.04° and 2.53 ± 1.85°, respectively. Sagittal angular deviations tended to increase in the cranial vertebra (C3 and C4) compared to the middle cervical spine.

CONCLUSIONS

We demonstrated that our patient-specific screw guide is vital for guiding precise screw insertion in the cervical pedicle. This technique may be an effective solution for achieving precise screw insertion and reducing the incidence of complications.

Computed Tomography-Based Navigation System in Current Spine Surgery: A Narrative Review

The number of spine surgeries using instrumentation has been increasing with recent advances in surgical techniques and spinal implants. Navigation systems have been attracting attention since the 1990s in order to perform spine surgeries safely and effectively, and they enable us to perform complex spine surgeries that have been difficult to perform in the past. Navigation systems are also contributing to the improvement of minimally invasive spine stabilization (MISt) surgery, which is becoming popular due to aging populations. Conventional navigation systems were based on reconstructions obtained by preoperative computed tomography (CT) images and did not always accurately reproduce the intraoperative patient positioning, which could lead to problems involving inaccurate positional information and time loss associated with registration. Since 2006, an intraoperative CT-based navigation system has been introduced as a solution to these problems, and it is now becoming the mainstay of navigated spine surgery. Here, we highlighted the use of intraoperative CT-based navigation systems in current spine surgery, as well as future issues and prospects.

Iatrogenic Vascular Injury Associated with Cervical Spine Surgery: A Systematic Literature Review

BACKGROUND

Iatrogenic vascular injury is an uncommon complication of anterior and/or posterior surgical approaches to the cervical spine. Although the results of this injury may be life-threatening, mortality/morbidity can be reduced by an understanding of its mechanism and proper management.

METHODS

We conducted a literature review to provide an update of this devastating complication in spine surgery. A total of 72 articles including 194 cases of vascular lesions following cervical spine surgery between 1962 and 2021 were analyzed.

RESULTS

There were 53 female and 41 male cases (in addition to 100 cases with unreported sex) with ages ranging from 3 to 86 years. The vascular injuries were classified according to the spinal procedures, such as anterior or posterior cervical spine surgery. The interval between the symptom of the vascular injury and the surgical procedure ranged from 0 to 10 years. Only two-thirds of patients underwent intra- or postoperative imaging and the most frequently injured vessel was the vertebral artery (86.60%). Laceration was the most common lesion (41.24%), followed by pseudoaneurysm (16.49%) and dissection (5.67%). Vascular repair was performed in 114 patients. The mortality rate was 7.22%, and 18.04% of patients had 1 or more other complications. Most presumed causes of vascular lesions were by instrumentation/screw placement (31.44%) or drilling (20.61%). Sixteen patients had an anomalous artery. Direct microsurgical repair was achieved in only 15 cases.

CONCLUSIONS

Despite increased anatomical knowledge and advanced imaging techniques, we need to consider the risk of vascular injury as a surgical complication in patients with cervical spine pathologies.

O-Arm Assisted Cervicothoracic Spine Pedicle Screw Placement Accuracy Is Higher Than C-Arm Fluoroscopy

OBJECTIVE

We compared the accuracy of C-arm fluoroscopy versus O-arm-assisted pedicle screw (PS) placement in the cervicothoracic spinal junction (CTSJ).

METHODS

Patients who underwent PS placement in the CTSJ (C7-T4) at our hospital were included in this study. Of 37 patients who underwent PS placement in the CTSJ, 20 underwent intraoperative C-arm fluoroscopy-assisted surgery (C Group) and 17 underwent intraoperative O-arm-assisted surgery (O Group). In total, 159 PSs were placed-73 in the C Group and 86 in the O Group. The accuracy of PS placement was compared between the C Group and O Group using the classification proposed by Gertzbein and Robbins to analyze pedicle violation.

RESULTS

PS accuracy was higher in the O Group than C Group; PS placement evaluated as grade A, representing no perforation, was 95.3% (82/86) for the O Group, whereas it was 78.1% (57/73) for the C Group. There was a clear statistically significant difference in accuracy of PS placement between the groups (P = 0.0013).

CONCLUSIONS

O-arm-assisted surgery improved the accuracy of PS placement in the CTSJ.

Power-Tool Use in Orthopaedic Surgery: Iatrogenic Injury, Its Detection, and Technological Advances: A Systematic Review

Power tools are an integral part of orthopaedic surgery but have the capacity to cause iatrogenic injury. With this systematic review, we aimed to investigate the prevalence of iatrogenic injury due to the use of power tools in orthopaedic surgery and to discuss the current methods that can be used to reduce injury.

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.

Intraoperative Computed Tomography for C1-C2 Stabilization by Goel-Harms: Analysis of Clinical Efficacy and a Novel Classification of Screw Placement Accuracy

BACKGROUND

The introduction of intraoperative computed tomography (iCT) could improve the surgical results of C1-C2 stabilization by Goel-Harms, especially in patients with complex deformities. This study aims to investigate the impact of iCT on the accuracy of C1-C2 screw positioning and to develop a score based on multiparametric analysis of imaging data (Cervical Screw Placement Accuracy score [CSPAs]).

METHODS

Twenty-one patients were retrospectively evaluated. The data obtained with the use of an iCT were compared with the incidence of cases of malpositioning in the literature. Multiparametric imaging criteria were developed: the 82 screw positions were evaluated using the CSPA criteria and 2 additional variables. The CSPAs was obtained from the aggregation of the CSPAs criteria: optimal (CSPAs ≥8), suboptimal (CSPAs = 6-7), malpositioned (CSPAs ≤5).

RESULTS

The average incidence of malpositioning in C1-C2 arthrodesis decreased from 13% without iCT to 1.2% with the aid of iCT, considering a monoparametric value. The CSPAs analysis shows a greater discretion and higher number of well-defined categories of the accuracy of C1-C2 screw position: optimal, 80.3%; suboptimal, 17.1%; and malposition, 2.6%. A correlation was observed between the accuracy of the positioning of both right and left screws in C2. Furthermore, the anatomic site of C2 screws was found to be a predictor of cortical invasion.

CONCLUSIONS

The results suggest that the introduction of the iCT is associated with a consistent improvement of the accuracy in the positioning of the screws. A multiparametric score (CSPAs) could improve the assessment of screw placement.

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.

Cervical Spine Navigation and Enabled Robotics: A New Frontier in Minimally Invasive Surgery

Background: Robotic-assisted and computer-assisted navigation (CAN) systems utilization has been rapidly increasing in recent years. Most existing data using these systems are performed in the thoracic, lumbar, and sacral spine. The unique anatomy of the cervical spine maybe where these technologies have the greatest potential. To date, the role of navigation-enabled robotics in the cervical spine remains in its early stages of development and study. Purpose: This review article describes the early experience, case descriptions and technical considerations with cervical spine screw fixation and decompression using CAN and robotic-assisted surgery. Methods: Representative cervical cases with early surgical experience with cervical and robotic assisted surgery with CAN. Surgical set up, technique considerations, instrumentation, screw accuracy and screw placement were elevated and recorded for each representative cervical case. Results: Existing robotic assisted spine surgical systems are reviewed as they pertain to the cervical spine. Method for cervical reference and positioning on radiolucent Mayfield tongs are presented. C1 lateral mass, odontoid fracture fixation, C2 pedicle, translaminar, subaxial lateral mass, mid cervical pedicle, navigated decompression and ACDF cases and techniques are presented. Conclusion: In conclusion, within the last several years, the use of CANs in spinal surgery has grown and the cervical spine shows the greatest potential. Several robotic systems have had FDA clearance for use in the spine, but such use requires simultaneous intraoperative fluoroscopic confirmation. In the coming years, this recommendation will likely be dropped as accuracy improves.

[Guideline-conform treatment of injuries to the subaxial cervical spine]

Injuries to the subaxial cervical spine are increasing and have an increased neurological risk compared to the thoracic and lumbar spines. The current treatment recommendations according to the therapeutic recommendations of the Spine Section of the German Society for Orthopedics and Trauma Surgery (DGOU) as well as the S1 guidelines of the German Trauma Society (DGU) are presented. This second part of the article describes the correct indications and treatment planning for injuries to the cervical spine. Based on the AOSpine classification for subaxial cervical spine injuries, decisions can be made about conservative or surgical treatment as well as individual details of the treatment. The underlying principles of treatment are relief of neurological structures, restoration of stability and reconstruction/preservation of the physiological alignment.

Free-Hand Cervical Pedicle Screw Placement by Using Para-articular Minilaminotomy: Its Feasibility and Novice Neurosurgeons' Experience

STUDY DESIGN.

Retrospective study.

OBJECTIVE.

Cervical pedicle screw (CPS) placement is technically demanding because of the great variation in pedicle size, dimension, and angulations between cervical levels and patients and the lack of anatomical landmarks. This retrospective study was conducted to analyze novice neurosurgeons' experience of CPS placement by using the technique with direct exposure of pedicle via para-articular minilaminotomy.

METHODS.

We retrospectively reviewed 78 CPSs in 22 consecutive patients performed by 2 surgeons. All pedicle screws were inserted under the direct visualization of the pedicle by using para-articular minilaminotomy without any fluoroscopic guidance. We analyzed the direction and grade of pedicle perforation on the postoperative computed tomography scan. The degree of perforation was classified as grade 0 to 3. Grades 0 and 1 were classified as the correct position and the others, as the incorrect position.

RESULTS.

In total, the correct position (grade 0 and 1) was found in 72 (92.3%) screws and the incorrect position (grade 2 and 3) in 6 (7.7%). Among the 16 pedicle perforations (grade 1, 2, and 3 perforations), the directions were lateral in 15 (93.8%) and superior in 1 (6.2%). There were no neurovascular complications related to CPS insertion.

CONCLUSION.

Free-hand CPS placement by using para-articular minilaminotomy seems to be feasible and reproducible.

Robotic Assistance for Minimally Invasive Cervical Pedicle Instrumentation: Report on Feasibility and Safety

BACKGROUND

Accurate screw placement remains challenging, especially in the cervical spine. We present our first experience of minimally invasive posterior cervical and upper thoracic pedicle screw fixation in the lower cervical spine.

METHODS

This study reports a case series of patients, undergoing posterior percutaneous pedicle fixation using Cirq robotic assistance coupled to the Airo intraoperative computed tomography scan and Brainlab navigation system. Routine computed tomography was performed on postoperative day 2 to evaluate pedicle screw placement. The effective dose was calculated.

RESULTS

Between February 2020 and December 2020, 7 patients (4 men and 3 women) were treated. The mean age was 58.8 years (range, 29-75 years). Fixation was performed with a cannulated PASS OCT Reconstruction System (Medicrea). Overall, 28 screws were placed within cervical and upper thoracic pedicles. According to the Neo and Heary classification, 85.7% were rated as acceptable and 14.3% as poor. The radiation dose received by the patient was 9.1 mSv (range, 7.7-10.6 mSv). The radiation dose received by the surgical staff was 0 mSv. The postoperative course was excellent.

CONCLUSIONS

Posterior miniopen fixation using Cirq robotic assistance coupled with an intraoperative computed tomography navigation system is a major innovation that can improve the accuracy of pedicle screw positioning, with acceptable patient radiation and reduced surgical team exposure.

Spinal Navigation for Cervical Pedicle Screws: Surgical Pearls and Pitfalls

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

We intend to evaluate the accuracy and safety of cervical pedicle screw (CPS) insertion under O-arm-based 3-dimensional (3D) navigation guidance.

METHODS

This is a retrospective study of patients who underwent CPS insertion under intraoperative O-arm-based 3D navigation during the years 2009 to 2018. The radiological accuracy of CPS placement was evaluated using their intraoperative scans.

RESULTS

A total of 297 CPSs were inserted under navigation. According to Gertzbein classification, 229 screws (77.1%) were placed without any pedicle breach (grade 0). Of the screws that did breach the pedicle, 51 screws (17.2%) had a minor breach of less than 2 mm (grade 1), 13 screws (4.4%) had a breach of between 2 and 4 mm (grade 2), and 4 screws (1.3%) had a complete breach of 4 mm or more (grade 3). Six screws were revised intraoperatively. There was no incidence of neurovascular injury in this series of patients. 59 of the 68 breaches (86.8%) were found to perforate laterally, and the remaining 9 (13.2%) medially. It was noted that the C5 cervical level had the highest breach rate of 33.3%.

CONCLUSIONS

O-arm-based 3D navigation can improve the accuracy and safety of CPS insertion. The overall breach rate in this study was 22.9%. Despite these breaches, there was no incidence of neurovascular injury or need for revision surgery for screw malposition.

Significance of Preoperative Prone Position Computed Tomography in Free Hand Subaxial Cervical Pedicular Screwing

OBJECTIVE

The subaxial cervical pedicle screwing technique shows powerful biomechanical properties for posterior cervical fusion. When applying a pedicle screw using the freehand technique, it is essential to analyse cervical computed tomography and plan the surgery accordingly. Normal cervical computed tomography is usually performed in the supine position, whereas during surgery, the patient lies in a prone position. This fact leads us to suppose that radiological evaluations may yield misleading results. Our study aimed to investigate whether there is any superiority between preoperative preparation on computed tomography performed in the prone position and that performed in the supine position.

METHODS

This study included 17 patients (132 pedicle screws) who were recently operated on with cervical vertebral computed tomography in the prone position and 17 patients (136 pedicle screws) who were operated on by conventional cervical vertebral computed tomography as the control group. The patients in both groups were compared in terms of age, gender, pathological diagnosis, screw malposition and complications. A screw malposition evaluation was made according to the Gertzbein-Robbins scale.

RESULTS

No statistically significant difference was observed between the two groups regarding age, gender and pathological diagnosis. The screw malposition rate (from 11.1% to 6.9%, p<0.05), mean malposition distance (from 2.18 mm to 1.86 mm, p <0.05), and complications statistically significantly decreased in the prone position computed tomography group.

CONCLUSION

Preoperative surgical planning by performing cervical vertebral computed tomography in the prone position reduces screw malposition and complications. Our surgical success increased with a simple modification that can be applied by all clinicians without creating additional radiation exposure or additional costs.

Current state of navigation in spine surgery

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

Long-Term Surgical Results of Skip Pedicle Screw Fixation for Patients with Adolescent Idiopathic Scoliosis: A Minimum-Ten-Year Follow-Up Study

Skip pedicle screw fixation for adolescent idiopathic scoliosis (AIS) requires fewer screws and can reduce the risk of neurovascular injury as compared with segmental pedicle screw fixation. However, the long-term impact of screw number reduction on correction and clinical results is unclear. This study examined the 10-year post-operative outcomes of skip pedicle screw fixation for patients with AIS. We reviewed the outcomes of 30 patients who underwent skip pedicle screw fixation for AIS. Radiological and clinical findings were assessed before and immediately, 2 years, and 10 years after surgery in the remaining 25 patients. The mean Cobb angle of the main curve preoperatively and immediately, 2 years, and 10 years post-operatively was 59.4°, 23.4°, 25.8°, and 25.60°, respectively, and was significantly improved at all post-surgical time points (all p < 0.001). The mean correction rate immediately after surgery was 60.8%, and the correction loss rate at the observation end point was 4.8%. The Cobb angle of the lumbar curve was significantly improved immediately after surgery, and the correction persisted until 10 years post-operatively. Remarkable gains were observed for most Scoliosis Research Society-22 patient questionnaire sub-scores at the final follow-up versus preoperative assessments. In conclusion, good correction of the AIS deformity by skip pedicle screw fixation was well maintained over a long follow-up period of 10 years, with clinically meaningful gains in Society-22 patient questionnaire sub-scores.

Vertebral Artery Terminating Posterior Inferior Cerebellar Artery (PICA-VA) as a Potential Risk Factor in Cervical Spine Surgery

OBJECTIVE

Unilateral vertebral artery (VA) injury is thought to not result in serious complications. The dominant-side VA should be preserved, although the importance of the nondominant-side VA has not been discussed. The injury of VA terminating posterior inferior cerebellar artery (PICA-VA) may result in cerebellar infarction. The characteristics of PICA-VA were evaluated.

METHODS

In study 1, results of head and neck magnetic resonance angiography were reviewed for 358 consecutive cases. VA diameter was measured at the V2 segment. Relationships between frequency of PICA-VA and asymmetry and diameter of the VA were analyzed. In study 2, results of magnetic resonance angiography were measured for 62 consecutive cases aged ≤39 years. Frequency of PICA-VA was compared between this young age group and 324 of the 358 cases aged ≥50 years.

RESULTS

Mean age for the total cohort was 67.8 ± 13.8 years (range, 10-94 years). PICA-VA was identified in 44 cases (12.3%). Mean diameter of all VAs was 3.2 ± 0.76 mm. Mean diameter of PICA-VA was 2.0 ± 0.55 mm, significantly smaller than the nondominant side in Confluence (+) (2.8 ± 0.59 mm; P < 0.001). Among the 56 VAs <2.0 mm, 26 (46.4%) were PICA-VA. PICA-VA was seen in 1 of the 62 cases aged ≤39 years (1.6%), and in 43 of the 324 cases aged ≥50 years (13.3%), showing a significantly lower frequency in the younger population (P < 0.001).

CONCLUSIONS

Whether PICA-VA injury causes complications is not obvious. However, PICA-VA should also be preserved considering that potential risks exist. If the VA is small or shows a large difference in diameter between sides, special care should be taken during cervical spine surgery.

Subaxial Cervical Pedicle Screw in Traumatic Spinal Surgery

In cases of unstable cervical traumatic lesions, the biomechanical superiority of the cervical pedicle screw (CPS) allows the lesion to be stabilized effectively. In this study, we review and summarize the indications, technical guidelines, and potential neurovascular complications and their prevention of the use of the CPS for trauma. For patients with fractured lamina or lateral mass, a CPS is reliable for stabilization. In addition, the CPS can penetrate through a linear cervical spinal pedicle fracture gap and could stabilize three-column injury. CPS reduce the range of surgical approach and preserve the motion segment using short-segment fixation. Fluoroscopy-guided CPS insertion is popular and cost-effective. Image-guided navigation systems improve accuracy. Three-dimensional template-guided CPS placement is simple to use. Most spine surgeons can perform laminoforaminotomy easily. Freehand technique that can be performed quickly without heavy equipment is suitable for emergency situation. Possible complications due to screw misplacement are vertebral artery injury owing to a laterally misplaced screw, dural sac or spinal cord injury from a medially misplaced screw, and nerve root injury caused by a superiorly or inferiorly misplaced screw. To prevent neurovascular complications, meticulous preoperative anatomical evaluation and following the five steps are most important.

The Subaxial Cervical Pedicle Screw for Cervical Spine Diseases: The Review of Technical Developments and Complication Avoidance

This study aimed to review information on the subaxial cervical pedicle screw (CPS) including recent anatomical considerations, entry points, placement techniques, accuracy, learning curve, and complications. Relevant literatures were reviewed, and the authors’ experiences were summarized. The CPS is used for reconstruction of unstable cervical spine and achieves superior biomechanical stability compared to other fixation techniques. Various insertion and guidance techniques are established, among which, lateral fluoroscopy-assisted placement is the most common and cost-effective technique. Generally, placement under imaging guidance is more accurate than other techniques, and a three-dimensional template allows optimal trajectory for each pedicle regardless of intraoperative changes in spinal alignment. The free-hand technique using a curved pedicle probe without a funnel-like hole increases screw stability and reduces operation time, radiation exposure, and soft tissue injury. Compared to conventional lateral fluoroscopy-assisted placement, free-hand CPS placement by trained surgeons achieves superior accuracy comparable to that of image-guided navigation; in general, 30 training cases are sufficient for learning a safe and accurate technique for CPS placement. The complications of subaxial CPS are classified into three categories: complications due to screw misplacement, complications without screw misplacement, and others. Inexperienced surgeons may benefit from advanced techniques; however, the accuracy of CPS ultimately depends on the surgeon’s experience. Inexperienced surgeons should master the placement of the thoracolumbar pedicle screw in real practice and practice CPS insertion using cadavers. During the initial phase of the learning curve, careful preparation of surgery, reiterated identification, patterned safety steps, and supervision of the expert are necessary.

Anatomic techniques for cervical pedicle screw placement

Instrumentation of the cervical spine with cervical pedicle screws (CPS) is beneficial in patients with various types of spinal pathology. Despite posing greater technical challenges, CPS instrumentation confers better fixation outcomes when compared to lateral mass screws. While developments in technology have augmented the accuracy of CPS insertion, mastery in freehand CPS insertion allows the aforementioned technologies to reach their full potential in improving patient outcomes. The aim of this article is to discuss freehand CPS insertion techniques as established in the current literature while sharing our experience in this context. A comprehensive literature search was performed using the following electronic databases: PubMed, Medline, and EMBASE. Full-text articles focusing on clinical studies with description of freehand techniques were included. Articles which were on cadaveric studies, drill jig, navigation or robotic technology were excluded. Thirteen primary references comprising 1,480 patients were included in this review. Majority of studies reported utilizing the cranial margin of lamina for C2 level as a landmark for entry point, as well as lateral to centre of the articular mass, and just medial to the lateral border of the superior articular process for C3-7 levels. Method of tracking and facilitation of trajectory was reported in multiple studies, with use of instruments ranging from curved pedicle probes to high-speed burrs. Limited studies reported specific trajectories of CPS insertion. Most studies noted testing pedicle wall integrity at various checkpoints, with pedicle screw repositioning or conversion to lateral screw mass following detection of perforation or screw malpositioning. Success in CPS insertion rests on meticulous preoperative planning to identify the ideal screw entry point and trajectory. Patient-specific drill jigs, navigation and robotic technologies, while beneficial to progress in the field of cervical spine surgery and patient outcomes, should serve primarily to augment good expertise in freehand CPS insertion technique.

A preliminary study of a novel robotic system for pedicle screw fixation: A randomised controlled trial

Background and objective

Existing orthopaedic robotic systems are almost restricted to provide guidance for trajectory direction. In the present study, a novel spinal robotic system with automatic drilling power was introduced. The aim of this study is to evaluate the feasibility and safety in pedicle screw ​insertion of posterior lumbar interbody fusion assisted by this novel robotic system.

Methods and materials

A randomised controlled trial was conducted for 17 participants who were required posterior lumbar interbody fusion process. Seven (3 M/4 F) were randomly assigned to the robot-assisted group (RA group), and the other ten (4 M/6 F) were assigned to the conventional technique group (FH group). A novel robotic system was used in the RA group. All measurements were based on postoperative computed tomography (CT) data. Accuracy of screw insertion was determined using the Gertzbein and Robbins Scale. Precision was measured by the entry point deviation distance and the trajectory rotation. Other variables included operation time, radiation time, length of stay, and screw-related complications.

Result

A total of 82 pedicle screws were placed in the 17 participants. In the RA group, 90.6% of screws placed were Grade A, and 9.4% were Grade B. In the FH group, 78.0% of screws were Grade A, 20.0% were Grade B, and 2.0% were Grade C. No statistical difference was found in the operation time, radiation time per case, and length of stay between both groups. The radiation time per screw is significantly lower in the RA group. No screw-related complications or revision occurred in the present study.

Conclusion

The outcome of screw accuracy of this robotic system was comparable with that of experienced surgeons, and no screw-related complication was found in the RA group during hospitalisation. In addition, radiation time per screw in the robotic group was significantly lower than that in the conventional group, which shows the potential to reduce radiation exposure of pedicle screw fixation assisted by this robotic system.

Translational potential

Our study shows that pedicle screw fixation assisted by "Orthbot" system is accurate and safe. It is concluded that this novel robotic system offers a new option for internal implantation in spine surgery.

Cortical Bone Trajectory Screws for Fixation Across the Cervicothoracic Junction: Surgical Technique and Outcomes

STUDY DESIGN

Clinical case series describing a novel surgical technique.

OBJECTIVE

Stabilization across the cervicothoracic junction (CTJ) poses technical difficulties which make this procedure challenging. The transition from cervical lordosis to thoracic kyphosis and the orientation of the lateral masses of the cervical spine compared with the pedicles of the thoracic spine create the need to accommodate for 2 planes of alignment when placing instrumentation. A novel surgical technique for instrumentation across the cervicothoracic junction is described.

METHODS

The use of cortical bone trajectory (CBT) technique for pedicle fixation in the upper thoracic spine is described in combination with cervical lateral mass or pedicle screws. The application in our first 12 patients for stabilization across the CTJ is described. Two case presentations illustrate the technique.

RESULTS

All the patients had rod screw constructs without the need to skip levels, there was no requirement for transverse connectors and only 1 plane of contouring was required.

CONCLUSIONS

The use of CBT technique has not been described for the upper thoracic spine. This technique avoids many technical problems associated with posterior instrumentation of the CTJ. The facility of their use in this application arises from the similar coronal plane entry points as the cervical lateral mass screws compared with the more lateral starting point of traditional thoracic pedicle screws. The technique has clinical equipoise to traditional thoracic pedicle screw insertion but with the benefits of an easier ability to perform the instrumentation and saving levels of fusion.

Robotic-Assisted Spine Surgery: History, Efficacy, Cost, And Future Trends

Robot-assisted spine surgery has recently emerged as a viable tool to enable less invasive and higher precision surgery. The first-ever spine robot, the SpineAssist (Mazor Robotics Ltd., Caesarea, Israel), gained FDA approval in 2004. With its ability to provide real-time intraoperative navigation and rigid stereotaxy, robotic-assisted surgery has the potential to increase accuracy while decreasing radiation exposure, complication rates, operative time, and recovery time. Currently, robotic assistance is mainly restricted to spinal fusion and instrumentation procedures, but recent studies have demonstrated its use in increasingly complex procedures such as spinal tumor resections and ablations, vertebroplasties, and deformity correction. However, robots do require high initial costs and training, and thus, require justification for their incorporation into common practice. In this review, we discuss the history of spinal robots along as well as currently available systems. We then examine the literature to evaluate accuracy, operative time, complications, radiation exposure, and costs - comparing robotic-assisted to traditional fluoroscopy-assisted freehand approaches. Finally, we consider future applications for robots in spine surgery.

A Review of the Historical Evolution, Biomechanical Advantage, Clinical Applications, and Safe Insertion Techniques of Cervical Pedicle Screw Fixation

Cervical spine instrumentation is evolving with an aim of stabilizing traumatic and non-traumatic cases of the cervical spine with a beneficial reduction, better biomechanical strength, and a strong construct with minimal intraoperative, as well as immediate and late postoperative complications. The evolution from interspinous wiring till cervical pedicle screws has changed the outlook in treating the cervical spine pathologies with maximum 3D stability, decreasing the duration of postoperative immobilization and hospital stay. Some complications associated with the use of cervical pedicle screw can be catastrophic. This review article discusses the morphometry of cervical pedicle; indications, biomechanical superiority, tricks, and pitfalls of cervical pedicle screw; complications and technical advancements in targeting safe surgery; and future directions of cervical pedicle screw instrumentation.

Screw view model of navigation in posterior corrective surgery for adolescent idiopathic scoliosis: A case report and technique note

RATIONALE

The purpose of this study is to introduce the application of screw view model of navigation (SVMN) for adolescent idiopathic scoliosis (AIS). It is a challenge to insert pedicle screw into the vertebral body of scoliosis, and the misplaced screw may lead to neurovascular injury. In order to minimize surgical complications, we used a novel method of SVMN technology to facilitate pedicle screw insertion.

PATIENT CONCERNS

Her mother brought her to our outpatient department upon noticing the girl's different heights of shoulders and unbalance of the trunk.

DIAGNOSES

She was diagnosed with AIS and syringomyelia.

INTERVENTIONS

We used an SVMN technology to assist pedicle screw insertion and correction surgery in this 20-year-old patient.

OUTCOMES

This study indicates that the SVMN could obtain a satisfactory surgical effect for AIS. The Cobb angle of segmental scoliosis (T7-L2) was 55° before surgery, and 3.5° after surgery, and the rate of correction was 93.6%. The segmental kyphosis (T7-L1) was 56.8° preoperatively and 32° postoperatively with the rate of correction of 43.6%. The distance between the center sacral vertical line (CSVL) and the C7 plumb line (CPL) was reduced from 56.2 mm to 0.2 mm, and the sagittal imbalance of 35.8 mm was improved to 3.5 mm. In addition, the misplacement of pedicle screws, the volume of blood loss, the operation time, and surgical complications were also recorded. The follow-up duration was 33 months.

LESSONS

The utilization of SVMN in AIS might reduce the incidence of screw misplacement and avoid neurovascular damage, as well as a satisfactory correction. The application of SVMN for AIS is an efficacious and safe method.

Reliability of an Intraoperative Radiographic Anteroposterior View of the Spinal Midline for Detection of Pedicle Screws Breaching the Medial Pedicle Wall in the Thoracic, Lumbar, and Sacral Spine

OBJECTIVE

The purpose of this study was to determine the sensitivity and specificity of using the spinal midline (M line) on a radiographic anteroposterior (AP) view for detecting pedicle screws (PSs) breaching the medial pedicle wall.

METHODS

We retrospectively reviewed 145 patients who underwent fusion surgery using PSs between January 2006 and May 2017. We defined the M line as a line that connected the upper and lower spinous processes through the fixed vertebrae. The M line was positive if the tip of the PS crossed the M line. The reference standard was a computed tomography scan. The reliability of the M line was examined.

RESULTS

The subjects included 145 patients (70 men and 75 women; mean age, 63.4 years). A total of 599 PSs were examined. Most cases were because of spondylolisthesis (66.9%). Most screws were inserted at a lower lumber level (77.6%). Analysis of the diagnostic accuracy of the M line yielded a sensitivity of 74.1% and a specificity of 95.3%. In addition, the positive predictive value of the M line was 42.6%, and the negative predictive value of the M line was 98.7%.

CONCLUSIONS

Assessment of the M line via an intraoperative radiographic AP view is a simple, readily available, complementary method for detecting PSs that have breached the medial pedicle wall in the thoracic, lumbar, and sacral spine. In particular, the M line has a strong negative predictive value, which is much more meaningful.

Radiologic analysis of pedicle marker for the cervical spine

PURPOSE

To elucidate the usefulness of the pedicle marker (PM) for more accurate insertion of cervical pedicle screws (CPSs).

METHODS

Artificial bone study. Fifty pedicles of five artificial bone specimens were examined. PMs were inserted in five different positions (confirmed by computed tomography (CT)); (1) insertion angle correct, insertion point too medial, (2) both insertion angle and insertion point correct, (3) insertion angle correct, insertion point too lateral, (4) insertion point correct, insertion angle too big, and (5) insertion point correct, insertion angle too small. Oblique radiographs were taken to assess the relationships between the pedicle and the PM as IN and OUT. Clinical series. A total of 228 CPSs were inserted in 59 consecutive patients using either CT cutout technique or navigation. During surgery, PMs were inserted, and the locations were confirmed on oblique fluoroscopic views in CT cutout technique and intraoperative CT in navigation. Intraoperative misplaced PM and postoperative misplaced CPS were assessed.

RESULTS

Artificial bone study. Evaluation found 67% of Types 1 and 100% of Type 5 seemed to be IN on the oblique views at 10, 20, and 30° because the pedicle and PM overlapped. All cases of Type 2 were IN at any angles. Almost all Types 3 and 4 were OUT at any angle. Clinical series. The route was modified under the recognition of misplaced PM during surgery in 3.7% (all Type 4) of CT cutout and 4.2% (four Type 4 and one Type 5) of navigation. One CPS was malpositioned (0.9%, Type 1) in CT cutout and none in navigation by postoperative CT.

CONCLUSIONS

By applying PM, lateral displacement is easier to recognize in fluoroscopy. Medial misplacement should be aware because the PM and the rim of the pedicle overlap. Even after launching navigation, PM helped to indicate the wrong route before inserting the CPS during surgery.

Can the position of the vertebral artery be predicted on a lateral view X-ray of the craniovertebral junction? A radiological anatomy study

Background

The most feared complication while inserting C2 screws is vertebral artery injury. This article proposes predicting the position of the vertebral artery on a true lateral X-ray of the axis vertebra from the background information acquired from the computed tomography (CT) scan utilizing fluoroscopy.

Methods

Spiral CT scans of 33 C2 vertebrae were performed utilizing a 16-slice CT scanner lateral X-rays of C2 were then obtained before and after painting the vertebral artery grooves with barium. The space available for transarticular and C2 pedicle screw insertion above the vertebral artery groove in the isthmus was then calculated as a ratio for both X-rays and CT scans.

Results

There was no statistically significant difference between the (mean) ratios calculated by CT scan and X-rays regarding the space available for transarticular and C2 pedicle screw insertion (left side: 0.3894 vs 0.3897; right side: 0.3892 vs 0.3925; P > 0.05). The Kappa test revealed that CT scan and X-ray findings were in agreement in majority of the bones (left side: n = 24, 72.7%, right side: n = 22, 73.3%; P < 0.05).

Conclusion

A thorough understanding of a true lateral view X-ray based on background information extracted from three dimensional CT scans helps predict the highest point of the vertebral artery groove. This proves useful for placement of C2 transarticular and pedicle screws during regular "open" and "minimally invasive" spine surgery.

An algorithmic strategy of surgical intervention for cervical degenerative kyphosis

PURPOSE

Correction surgery for cervical degenerative kyphosis (CDK) may carry a greater risk of causing neural complications such as spinal cord injury and C5 nerve palsy because spinal canal stenosis, osteoarthritis of the facet, and consequent foraminal stenosis may coexist with CDK. We have produced an algorithmic strategy of surgical intervention for CDK, and report the outcome.

METHODS

Thirty-one patients who underwent correction surgery for CDK, with a kyphotic angle of 20° or more (from 20 to 74) were involved. An algorithmic surgical strategy is shown. Clinical and radiological outcomes were examined amongst the groups.

RESULTS

Recovery rate of the JOA score was a mean of 44%. Preoperative kyphotic angle and correction angle were; 24.4°and 26.5°in P, 38.4°and 41.1°in AP, and 42.0°and 46.9°in PAP respectively. No spinal cord injury was found. Five cases of C5 nerve palsy occurred in P, and one in AP. Four cases of C5 palsy occurred in seven patients in PAP, although prophylactic foraminotomy was performed. All C5 palsy patients recovered fully at follow-up.

CONCLUSIONS

This study showed that our algorithmic surgical strategy for CDK is acceptable because we obtained good outcomes, and no catastrophic complications occurred. Although we did not intend to obtain excessive postoperative lordosis, we still had several incidence of C5 nerve palsy. We have to be aware of this incidence in PAP, which required a massive range of realignment. The incidence occurred even after we performed prophylactic foraminotomy, however, this procedure may lessen the severity of C5 palsy because those were all transient.

Cervical Pedicle Screw Placement Using Medial Funnel Technique

OBJECTIVE

Cervical pedicle screw (CPS) placement is very challenging due to high risk of neurovascular complications. We devised a new technique (medial funnel technique) to improve the accuracy and feasibility of CPS placement.

METHODS

We reviewed 28 consecutive patients undergoing CPS instrumentation using the medial funnel technique. Their mean age was 51.4 years (range, 30-81 years). Preoperative diagnosis included degenerative disease (n=5), trauma (n=22), and infection (n=1). Screw perforations were graded with the following criteria: grade 0 having no perforation, grade 1 having <25%, grade 2 having 25%-50% and grade 3 having >50% of screw diameter. Grades 0 and 1 were considered as correct position. The degree of perforation was determined by 2 junior neurosurgeons and 1 senior neurosurgeon.

RESULTS

A total of 88 CPSs were inserted. The rate of correct placement was 94.3%; grade 0, 54 screws; grade 1, 29 screws; grade 2, 4 screws; and grade 3, 1 screw. No neurovascular complications or failure of instrumentation occurred. In perforated screws (34 screws), lateral perforations were 4 and medial perforations were 30.

CONCLUSION

We performed CPS insertion using medial funnel technique and achieved 94.3% (83 of 88) of correct placement. And it can decrease lateral perforation.

Safe placement of lateral mass screw in the subaxial cervical spine: a case series

PURPOSE

Laminectomy with lateral mass screw fixation has been proven to be an effective method to treat the multilevel cervical degenerative myelopathy and severe cervical spondylosis. However, accurate and safe insertion of the lateral mass screw is technically demanding due to the individual variations of the anatomy of the lateral mass of the subaxial cervical spine. Misplaced lateral mass screw is not uncommon, and operation-related complications still beset the surgeons, which may impair the clinical outcomes. This study aimed to introduce a novel strategy for safe and accurate insertion of lateral mass screw in the subaxial cervical spine.

METHODS

From July 2014 to March 2015, 24 patients with multilevel cervical degenerative myelopathy at C3-C6 levels received laminectomy. Before the operation, the screw insertion technique depended on the pre-operative imaging and operative exploration. Following this strategy, the lateral mass screws were inserted into the subaxial cervical spines. Post-operative radiograph was performed to observe the locations of the lateral mass screws and the cervical curvature. Patients were followed up, and the functional neurological recovery was evaluated by the modified Japanese Orthopedic Association (JOA) disability scale, the Neck Disability Index (NDI) and NDI ranking system.

RESULTS

All screws were inserted into the lateral mass of C3-C6 cervical vertebrae following the current technique. Post-operative CT scans confirmed all screws inserted into the safe zone and relative safe zone of the lateral mass without any screw placed into the transverse foramen. The angle between the lateral mass screw and the vertical line was 40.49 ± 5.44 degrees on the axial CT images. Twenty-four patients were followed up for an average of 25.79 months (range, 20-30 months), and 22 cases evaluated as no or mild disability. According to the JOA score, NDI score and NDI ranking system, the postoperative function of the patients was significantly better when compared with their preoperative corresponding data (all p < 0.001) CONCLUSION: Inserting lateral mass screw following this new strategy is safe and easy to perform without any screw-related neurovascular complications, which contribute to the rigid fixation of the subaxial cervical spine and the satisfactory functional recovery.

Differences between Manufacturers of Computed Tomography-Based Computer-Assisted Surgery Systems Do Exist: A Systematic Literature Review

STUDY DESIGN

Literature review.

OBJECTIVE

Several studies have shown that the accuracy of pedicle screw placement significantly improves with use of computed tomography (CT)-based navigation systems. Yet, there has been no systematic review directly comparing accuracy of pedicle screw placement between different CT-based navigation systems. The objective of this study is to review the results presented in the literature and compare CT-based navigation systems relative only to screw placement accuracy.

METHODS

Data sources included CENTRAL, Medline, PubMed, and Embase databases. Studies included were randomized clinical trials, case series, and case-control trials reporting the accuracy of pedicle screws placement using CT-based navigation. Two independent reviewers extracted the data from the selected studies that met our inclusion criteria. Publications were grouped based on the CT-based navigation system used for pedicle screw placement.

RESULTS

Of the 997 articles we screened, only 26 met all of our inclusion criteria and were included in the final analysis, which showed a significant statistical difference (p < 0.0001, 95% confidence interval 0.92 to 1.23) in accuracy of pedicle screw placement between three different CT-based navigation systems. The mean (weighted) accuracy of pedicle screws placement based on the CT-based navigation system was found to be 97.20 ± 2.1% in StealthStation (Medtronic, United States) and 96.1 ± 3.9% in VectorVision (BrainLab, Germany).

CONCLUSION

This review summarizes results presented in the literature and compares screw placement accuracy using different CT-based navigation systems. Although certain factors such as the extent of the procedure and the experience and skills of the surgeon were not accounted for, the differences in accuracy demonstrated should be considered by spine surgeons and should be validated for effects on patients' outcome.

Screw perforation rates in 359 consecutive patients receiving computer-guided pedicle screw insertion along the cervical to lumbar spine

PURPOSE

Pedicle screw (PS) insertion has been criticized for its risk of serious injury to neurovascular structures. Although computed tomography (CT)-based navigation has been developed to avoid such complications, perforation remains an issue, even with the aid of additional guidance. We clarify screw perforation rate and direction in 359 consecutive patients treated using CT-based PS insertion and present important considerations for more accurate screw placement.

METHODS

The medical records of 359 consecutive patients who underwent PS insertion involving C2-L5 using a CT-based navigation system were reviewed. Postoperative CT images were analyzed to evaluate the accuracy of screw placement. We investigated both rate and direction of screw perforation according to vertebral level.

RESULTS

Of the 3413 PS that were inserted, 6.9% were judged as Grade 2 or 3 perforations. The combined rate of these perforations was 5.0% for C2, 11.4% for C3-5, 7.0% for C6-7, 10.4% for T1-4, 8.8% for T5-8, 4.5% for T9-12, and 3.8% for L1-5. We also analyzed the odds ratio (OR) for screw perforation in vertebrae accounting for the effects of age and disease. Multivariate analysis identified that PS insertions at C3-5 (OR 2.9, 95% CI 1.6-5.1; p < 0.001), T1-4 (OR 2.7, 95% CI 1.6-4.7; p < 0.001), and T5-8 (OR 2.3; 95% CI 1.4-3.8; p = 0.001) were significantly associated with Grade 2 or 3 screw perforation as compared with that of L1-5.

CONCLUSIONS

Even with CT-based navigation, careful insertion of PS is needed in the middle cervical spine because of a significantly higher perforation rate as compared with the lumbar region.

An Assessment of the Medial Angle of Inserted Subaxial Cervical Pedicle Screw during Surgery: Practical Use of Preoperative CT Scanning and Intraoperative X-rays

The most important factor for cervical pedicle screw placement (CPS) is creating a sufficient medial angle. We aimed to know the medial angle of the inserted subaxial CPS during surgery using intraoperative AP X-rays. From March 2012 to September 2014, we performed posterior cervical fusions using CPS on 75 patients, including a total of 389 CPS insertions. Using preoperative CT scanning, we determined the θ_lat (i.e., an angle between a vertical line and a line to connect the planned entry point and the axial middle point of the pedicle) and θ_med (i.e., an angle between a vertical line and a line to connect a new medial entry point and the axial middle point of the pedicle; this angle was regarded as minimally acceptable and a safe medial angle). The actual inserted medial angle (θ_ins) was checked and we determined whether it was between the θ_med and θ_lat in the accurately placed CPS, and not in the laterally violated CPS. We measured the horizontal distance of the CPS body (l; using an intraoperative AP X-ray). If the actual screw length (L) was known, we could calculate the medial angle (θ_AP) as sin⁻¹l / L. We checked the θ_AP and θ_ins for all of the same levels. Intra- and inter-observer agreement was analyzed. Among 368 accurately inserted CPSs, we found that 360 of the θ_ins values were greater than or equal to the θ_med on the same level (P <0.001). The intra-observer agreements were 0.781 and 0.847. The inter-observer agreements were 0.917 and 0.949. It was important that θ_ins was greater than or equal to the θ_med. Our suggested formula, θ_AP = sin⁻¹l / L, seems to be useful for predicting the medial angle of the inserted CPS and for comparing it with θ_med during surgery based on an AP X-ray and preoperative CT scan.

Image-guided Spine Stabilization for Traumatic Or Osteoporotic Spine Injury: Radiological Accuracy and Neurological Outcome

Significant progress has been made in image-guided surgery (IGS) over the last few decades. IGS can be effectively applied to spinal instrumentation surgery. In the present study, we focused our attention on the feasibility and safety of image-guided spine stabilization for traumatic or osteoporotic spine injury. The IGS spine fixation with or without minimally invasive surgery (MIS) techniques such as percutaneous screw placement, balloon kyphoplasty (BKP), or vertebroplasty (VP) were accomplished in 80 patients with traumatic or osteoprotic spine injury between 2007 and 2015. The injured vertebral levels included the following: cervical spine, 41; thoracic spine, 22; and lumbar spine, 17. Neurological condition before and after surgery was assessed using the American Spinal Injury Association Impairment Scale (AIS). A total of 419 pedicle, lateral mass, or laminar screws were placed, and 399 screws (95.2%) were found to be placed correctly based on postoperative computed tomography scan. Although 20 screws (4.8%) were found to be unexpectedly placed incorrectly, no neural or vascular complications closely associated with screw placement were encountered. Neurological outcomes appeared to be acceptable or successful based on AIS. The IGS is a promising technique that can improve the accuracy of screw placement and reduce potential injury to critical neurovascular structures. The integration of MIS and IGS has proved feasible and safe in the treatment of traumatic or osteoporotic spine injury, although a thorough knowledge of surgical anatomy, spine biomechanics, and basic technique remain the most essential aspects for a successful surgery.

Screw Placement Accuracy and Outcomes Following O-Arm-Navigated Atlantoaxial Fusion: A Feasibility Study

Study Design Case series of seven patients. Objective C2 stabilization can be challenging due to the complex anatomy of the upper cervical vertebrae. We describe seven cases of C1-C2 fusion using intraoperative navigation to aid in the screw placement at the atlantoaxial (C1-C2) junction. Methods Between 2011 and 2014, seven patients underwent posterior atlantoaxial fusion using intraoperative frameless stereotactic O-arm Surgical Imaging and StealthStation Surgical Navigation System (Medtronic, Inc., Minneapolis, Minnesota, United States). Outcome measures included screw accuracy, neurologic status, radiation dosing, and surgical complications. Results Four patients had fusion at C1-C2 only, and in the remaining three, fixation extended down to C3 due to anatomical considerations for screw placement recognized on intraoperative imaging. Out of 30 screws placed, all demonstrated minimal divergence from desired placement in either C1 lateral mass, C2 pedicle, or C3 lateral mass. No neurovascular compromise was seen following the use of intraoperative guided screw placement. The average radiation dosing due to intraoperative imaging was 39.0 mGy. All patients were followed for a minimum of 12 months. All patients went on to solid fusion. Conclusion C1-C2 fusion using computed tomography-guided navigation is a safe and effective way to treat atlantoaxial instability. Intraoperative neuronavigation allows for high accuracy of screw placement, limits complications by sparing injury to the critical structures in the upper cervical spine, and can help surgeons make intraoperative decisions regarding complex pathology.

Surgical safety of cervical pedicle screw placement with computer navigation system

Cervical pedicle screw (CPS) may be the biomechanically best system for posterior cervical segmental fixation, but may carry a surgery-related risk. The purpose of this study was to evaluate the safety of CPS placement using computer navigation system for posterior cervical instrumented fixation and discuss its complication avoidance and management. Posterior cervical instrumented fixation using CPS was performed in a total of 128 patients during the period between 2007 and 2015. Intraoperative image guidance was achieved using a preoperative 3D CT-based or an intraoperative 3D CT-based navigation system. A total of 762 CPSs were placed in the spine level of C2 to Th3. The radiological accuracy of CPS placement was evaluated using postoperative CT. Accuracy of CPS placement using a preoperative 3D CT-based navigation system was 93.6 % (423 of 452 screws) in grade 0; the screw was completely contained in the pedicle, and accuracy of CPS placement using an intraoperative 3D CT-based navigation system was a little bit improved to 97.1 % (301 of 310 screws) in grade 0. CPS misplacement (more than half of screw) was 3.3 % (15 of 452 screws) using a preoperative 3D CT-based navigation system, and CPS misplacement (more than half of screw) was 0.6 % (2 of 310 screws) using an intraoperative 3D CT-based navigation system. In total, 38 screws (5.0 %) were found to perforate the cortex of pedicle, although any neural or vascular complications closely associated with CPS placement were not encountered. Twenty nine of 38 screws (76.3 %) were found to perforate laterally, and seven screws (18.4 %) were found to perforate medially. Image-guided CPS placement has been an important advancement to secure the safe surgery, although the use of CPS placement needs to be carefully determined based on the individual pathology.

Posterior Fixation Techniques in the Subaxial Cervical Spine

This article reviews the historical context, indications, techniques, and complications of four posterior fixation techniques to stabilize the subaxial cervical spine. Specifically, posterior wiring, laminar screw fixation, lateral mass fixation, and pedicle screw fixation are among the common methods of operative fixation of the subaxial cervical spine. While wiring and laminar screw fixation are now rarely used, both lateral mass and pedicle screw fixation are technically challenging and present the risk of significant complications if performed incorrectly. With a sound understanding of anatomy and rigorous preoperative evaluation of bony structures, both lateral mass and pedicle screw fixation provide a safe and reliable method for subaxial cervical spine fixation.

Comparing Accuracy of Cervical Pedicle Screw Placement between a Guidance System and Manual Manipulation: A Cadaver Study

Background

The aim of this study was to compare the accuracy of cervical pedicle screw placement between a three-dimensional guidance system and manual manipulation.

Material/Methods

Eighteen adult cadavers were randomized into group A (n=9) and group B (n=9). Ninety pedicle screws were placed into the C3-C7 under the guidance of a three-dimensional locator in group A, and 90 screws were inserted by manual manipulation in group B. The cervical spines were scanned using computed tomography (CT). Parallel and angular offsets of the screws were compared between the two placement methods.

Results

In group A, 90% of the screws were within the pedicles and 10% breached the pedicle cortex. In group B, 55.6% were within the pedicle and 44.4% breached the pedicle cortex. Locator guidance showed significantly lower parallel and angular offsets in axial CT images (P<0.01), and significantly lower angular offset in sagittal CT images (P<0.01) than manual manipulation.

Conclusions

Locator guidance is superior to manual manipulation in accuracy of cervical screw placement. Locator guidance might provide better safety than manual manipulation in placing cervical screws.