Three-Dimensional Printed Model-Assisted Screw Installation in Treating Posterior Atlantoaxial Internal Fixation

Efficacy and Safety of Goel-Harms Technique in Upper Cervical Spine Surgery: A Systematic Review and Meta-Analysis

OBJECTIVE

The main purpose of this systematic review and meta-analysis was to estimate the incidence of implant-associated complications and fusion rates for the Goel-Harms technique (GHT) and to show potential factors affecting the complications and nonunion development.

METHODS

A systematic search of the PubMed database according to PRISMA guidance was performed. The main inclusion criteria comprised description of fusion rate and/or implant-associated complications rate.

RESULTS

This systematic review included 86 articles focused on the results of surgery in 4208 patients. The rate of screw-related complications was as follows: 1) vertebral artery (VA) injury, 2.8%; 2) screw malposition in the direction of the VA, 5.8%; and 3) C2 nerve root irritation, 6.1%. The nonunion rate was 4.2%. Transpedicular screw insertion to the C1 and C2 vertebrae were the safest regarding VA injury and correlated with lower blood loss. For C1-C2 fusion, there was no statistical difference for the different bone graft localization. C2 nerve root irritation rate did not depend on screw insertion technique. The use of a freehand technique did not correlate with a high rate of screw-related complications.

CONCLUSIONS

The Goel-Harms technique is a promising method of C1-C2 fusion, with a relatively low nonunion and VA injury rate. It can be performed safely without C-arm or navigation system assistance. Transpedicular screw insertion trajectories to the C1 and C2 vertebrae were safest regarding VA injury and blood loss volume. Further comparative studies of various C1-C2 stabilization methods with a high level of significance should be carried out to identify the optimal approach.

Prediction of the functional and radiological outcome on the basis of independent factors with special emphasis on the use of 3D printed models in craniovertebral junction surgery

Background:

The aim of the study was to evaluate the advantage of performing planned surgery using customized three-dimensional (3D) printed models versus performing surgery without using 3D printed models in patients with craniovertebral junction (CVJ) anomalies and traumatic CVJ fractures and dislocations.

Methods:

Forty-two patients with CVJ anomalies, who were planned for operative intervention in the Department of Neurosurgery at SMS Hospital from March 2019 to February 2021, were randomly divided into two groups and analyzed. First group was operated after rehearsal on a customized 3D printed model whereas the second group underwent operative intervention without the rehearsal of surgery on the 3D printed model.

Results:

Forty-two patients were enrolled for the study. Twenty-five of these patients had developmental CVJ anomalies, 16 had post traumatic Atlantoaxial dislocation (AAD), and one had congenital AAD. Twenty-three patients underwent surgical intervention using 3D printed models and 19 without using 3D printed models. The outcome in the two groups was compared using modified Japanese orthopedic association score (mJOA), recovery rate, incidence of complications such as screw malposition, postoperative neurological deterioration, vertebral artery (VA) injury, and radiological improvement based on Atlanto-Dental interval, the distance of the tip of dens from Wackhenheims clivus canal line, and the distance of tip of dens from the Chamberlain’s line. The improvement in mJOA score postoperatively was found to be statistically significant in study group (P < 0.001) as compared to control group (P = 0.06). Recovery rate was better in study group than in control group (P = 0.023). In study group, the incidence of screw malposition and VA injury was lower than control group. Three patients deteriorated neurologically postoperatively in the control group and none in the study group. The average improvements in the radiological parameters were found to be better in study group as compared to control group postoperatively.

Conclusion:

The authors conclude that 3D printed models are extremely helpful in analyzing joints and VA anatomy preoperatively and are helpful in unmasking any abnormal bony and vascular anatomy effectively, making the surgeon confident about the placement of the screws intraoperatively. These 3D models help in intraoperative error minimization with better neurological outcomes in postoperative period. In our opinion, these models should be included as a basic investigation tool in patients of CVJ abnormalities. The models also offer other advantages such as preoperative simulation, teaching modules, and patient education.

Biomechanical Effects of Lateral Inclination C1 and C2 Pedicle Screws on Atlantoaxial Fixation

Objective

To assess the biomechanical effect of lateral inclination C₁ and C₂ pedicle screws on the atlantoaxial fixation through vitro human cadaveric study.

Methods

From January 2016 to December 2017, fresh‐frozen cadaveric cervical spines with intact ligaments from eight donated cadavers at an average age of 71.5 ± 10.6 years, comprising of six males and two females, were collected. There were no fracture and congenital malformation in all specimens according to the imaging examination. The range of motion (ROM) of the specimens were tested in their intact condition and destabilized condition. Next, the specimens were randomly divided into two groups to ensure no differences in sex and age: Group 1 was medial inclination C₁ pedicle screw and C₂ pedicle screws (C₁MPS‐C₂PS) and Group 2 was lateral inclination C₁ pedicle screw and C₂ pedicle screws (C₁LPS‐C₂PS). The ROM of the fixation scenarios were recorded. Thereafter, all the specimens with fixation constructs were tested for 1,000 cycles of axial rotation and tensile loading to failure was carried out collinearly to the longitudinal axis of all the screws, the data were documented as screw pullout strength (SPS) in newtons. All the recorded data subjected to quantitative analysis.

Results

The ROM of specimens was increased significantly in destabilized condition and significantly reduced in fixation condition compared with intact condition. In C₁LPS‐C₂PS groups, the C₁‐C₂ cervical segment showed 3.96° ±1.21° and 3.75° ± 1.33° in flexion and extension direction, 2.85° ± 0.91° and 2.96° ± 0.71° in right and left lateral bending, 2.20° ± 0.43° and 2.15° ± 0.40° in right and left axial rotation. In C₁MPS‐C₂PS groups, it showed 4.24° ±1.31° and 3.98° ± 1.21° in flexion and extension direction, 2.76° ± 1.10° and 3.23° ± 0.62° in right and left lateral bending, 2.20° ± 0.46° and 2.21° ± 0.42° in right and left axial rotation. There was no statistically significant difference on ROM and screw pullout strengths (764.29 ± 129.00 N vs 714.55 ± 164.63 N) between the two groups. However, there was one specimen in the C₁MPS‐C₂PS group showing rupture the inferior wall of the left screw trajectory owing to the relatively thin posterior arch of the atlas, the screw pullout strength was significantly reduced (left pullout strength value: 430.5 N, right pullout strength value: 748.4 N). Therefore, in the case of the thin posterior arch of the atlas, the C₁LPS‐C₂PS group had strong long‐term biomechanics.

Conclusion

The lateral inclination C₁ pedicle screw can achieve the same biomechanical strength as the traditional atlas pedicle screw. However, for the case where the posterior arch of the atlas is relatively thin, a lateral inclination C₁ pedicle screw is more suitable.

Accuracy of pedicle screw placement by fluoroscopy, a three-dimensional printed model, local electrical conductivity measurement device, and intraoperative computed tomography navigation in scoliosis patients

INTRODUCTION

There are several assisted methods for the accurate placement of pedicle screw (PS), including fluoroscopy, a three-dimensional (3D) printed model, a local electrical conductivity measurement device (LECMD), and intraoperative computed tomography (CT) navigation.

OBJECTIVES

This study aimed to investigate the accuracy of PS placement and clinical results using different assisted methods.

METHODS

This study included 553 pedicle screws in 31 patients. We divided patients into the fluoroscopy (F) group (n = 79), 3D printed model and fluoroscopy (3D + F) group (n = 150), LECMD, 3D printed model, and fluoroscopy (LECMD + 3D + F) group (n = 171), and the intraoperative CT navigation (N) group (n = 153). We evaluated the operative time, intraoperative bleeding, number of fusion vertebrae, correction rate of the main curve, apical vertebral translation, grade of PS perforation (Grade 0: no perforation; Grade 1: < 2 mm; Grade 2: 2‒4 mm; Grade 3: > 4 mm), and accuracy of PS placement.

RESULTS

The N group had a significantly longer operative time. There were no significant differences in the clinical results excluding the operative time. The accuracy of PS placement was 93.7%, 91.3%, 93.6%, and 93.5% in the F, 3D + F, LECMD + 3D + F, and N groups, respectively. The Grade 2 perforation rate was 2.5%, 0%, 0.6%, and 0.7% in the F, 3D + F, LECMD + 3D + F, and N groups, respectively.

CONCLUSIONS

There were no significant differences in the accuracy of PS placement and clinical results excluding the operative time. The 3D printed model, LECMD, or intraoperative CT navigation would be useful to prevent Grade 2 perforation.

Three-Dimensional-Printed Model-Assisted Management of Craniovertebral Junction Abnormalities: An Institutional Experience with Literature Review

Study Design

Prospective study.

Purpose

To evaluate the utility and limitations of using three-dimensional (3D)-printed models for the management of craniovertebral (CV) junction abnormalities.

Overview of Literature

In comparison to other bony and vascular anomalies, CV junction abnormalities are difficult to treat. For cases of irreducible atlantoaxial dislocation (AAD), posterior reduction and stabilization have replaced anterior decompression as the standard management protocol. The use of 3D models, such as those described herein, can provide surgeons with in-depth knowledge of the vertebral artery course and bony anomalies associated with CV junction abnormalities.

Methods

Clinical and radiological features of 18 patients with CV junction abnormalities were analyzed between March 2017 and February 2019 at Sawai Man Singh Medical College, Jaipur, India. Dynamic computed tomography (CT) of the CV junction and CT angiographies of the neck with respect to the vertebral artery course at the C1–C2 joints were obtained and studied. Customized 3D models of the CV junction were then made based on the CT data, and rehearsal of the surgical procedure was performed using the 3D model one day prior to performing the actual procedure.

Results

Seventeen patients had congenital-type AAD, whereas one patient had posttraumatic AAD. Improvements in neck pain and myelopathy were seen in all patients at the follow-up, as analyzed using the Visual Analog Scale and the Japanese Orthopedic Association Scale score, respectively. There were no cases of malpositioning of screws or any direct vertebral artery injury, although in one patient, the distal flow in the dominant vertebral artery was cut off as it got compressed between the bony arch and the screw head.

Conclusions

Compared to computer-generated images, 3D-printed models are a more practical approach for dealing with complex CV junction abnormalities. They provide surgeons with deep insights into the complex bony anomalies as well as variations in the vertebral artery courses, thereby improving surgical outcomes.

Accuracy of Bony Gutter Placement in Cervical Laminoplasty Assisted by 3-D Print Modeling, and Associations with Posterior Spinal Cord Shift and Radiculopathy

Introduction

We evaluated the positioning of the bony gutter (PBG) in cervical laminoplasty aided by three-dimensional (3-D) printed models, and assessed associations between PBG accuracy¸ posterior shift of the spinal cord (PSSC), and clinical results.

Methods

Of 35 patients who underwent cervical laminoplasty for cervical myelopathy between January 2013 and September 2015, 20 were treated using a conventional free-hand technique (Group A). For the other 15 patients (Group B), surgeons also used 3-D printed models to select a PBG on the edge of the medial aspect of the zygapophyseal joint to maximize the angle of the opened lamina (AOL). We measured the PBG and AOL on axial computed tomography images, and the PSSC on midsagittal magnetic resonance imaging obtained before and 7 days after surgery. Clinical outcomes were evaluated by Japanese Orthopaedic Association (JOA) scores and recovery rates, and by the incidence of postoperative radiculopathy. We compared the PBG, AOL, PSSC, and clinical outcomes between the groups.

Results

The PBG was significantly lower in Group B than in Group A at the C4 left and right sides (P = 0.033, P < 0.0001) and C6 left side (P = 0.004), and the AOL was larger at the C4 right side, C5 left and right sides, C6 left side, and C7 right side (P = 0.040, 0.043, 0.016, 0.016, and 0.027, respectively). Group B had a higher percentage of on-target PBGs at the right sides of C4 and C5 and the left side of C7 (P = 0.005, 0.037, and 0.028), a larger PSSC at C4 and C5 (P = 0.023, 0.008), and a higher incidence of radiculopathy (P = 0.026). Groups A and B did not differ significantly in JOA score or recovery rate.

Conclusions

Three-dimensional modeling improved PBG accuracy. However, maximizing the spinal canal increased the PSSC and subsequent radiculopathy.