Creation of 3-Dimensional Life Size: Patient-Specific C1 Fracture Models for Screw Fixation

doi:10.1016/j.wneu.2018.02.131

World Neurosurgery

Volume 114, June 2018, Pages e173-e181

https://doi.org/10.1016/j.wneu.2018.02.131 Get rights and content

Highlights

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C1 screws require analysis of the complex osteovascular structures of the personalized anatomical variations.
•
3D life-size models were assisted in determining the fracture location, pedicle size and VA shapes.
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3D invidualized models are useful for neurosurgeons, improving an important supplement to their training and experience.
•
3D models are helping patients and their families to understand their cases, surgical goals and risks of the operation.

Background

Transarticular screw fixation has fatal complications such as vertebral artery (VA), carotid artery, and spinal cord injuries. The landmarks for deciding the entry point for C1 lateral mass screws were clarified by using life-size 3-dimensional (3D) patient-specific spine models.

Methods

This study included a total of 10 patients with C1 fractures. Dual-energy computed tomography (CT) scan data from C1 pre- and postscrewing were modified into 3D patient-specific life-size cervical spine models. The detailed information, such as bony and vascular elements, of 13 separate parameters of C1 was used as an intraoperative reference.

Results

3D patient-specific models were created preoperatively with the fracture and postoperatively with the screwed vertebrae. After CT scans of the models were measured, the life-size patient-specific models were proven to be individualized. 3D models assisted in determining the fracture locations, pedicle sizes, and positions of the VA. The range of the measurements for ideal point of entry reveals the need for patient-specific intervention was required.

Conclusions

3D models were used in surgical planning maximizing the possibility of ideal screw position and providing individualized information concerning cervical spinal anatomy. The individualized 3D printing screw insertion template was user-friendly, of moderate cost, and it enabled a radiation-free cervical screw insertion.

Introduction

C1 fractures, atlantoaxial subluxation, trauma, tumor, infection, rheumatoid arthritis, and congenital malformations can be treated with screw fixation in the area.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 Various factors take part in performing this procedure, including complex anatomic relationships among structures such as the vertebral artery (VA), internal carotid artery, cervical nerve roots, ligaments, cervical curvature, and horizontal articular surfaces. However, cervical spine screw fixation is still challenging because of the complexity of the anatomy of the cervical area, bleeding from the venous plexus, injury to the hypoglossal nerve or VA, and postoperative occipital neuralgia caused by C2 nerve root injury.6, 13, 14 Especially, VA injury can be serious and has potentially life-threatening complications in cervical screw fixation.6, 13, 14 Generally, the VA is the vessel that is at maximum risk (0%–16.7%) during these procedures because of its close relationship with the entry site and trajectory of the screws.15, 16

Given the personalized anatomic details of the cervical spine complex, proper pedicle screw positioning can be arduous with increased operative time and a potentially higher complication rate, which could result in poor outcome, especially in patients with pedicle hypoplasia or aberrant VA course, patients with cervicothoracic kyphoscoliosis, and elderly patients.7, 17 Inexperienced surgeons have been shown to have a higher risk of causing VA insufficiency, screw malpositions, or neurologic deficit, pseudarthrosis, or required operative revision or removal.18, 19

Three-dimensional (3D) models have been used in applications in many surgical and medical fields, including cranial construction, maxillofacial fracture, tissue engineering, vascular patching, thoracic deformities, complex spinal surgery, and trauma.20, 21, 22, 23 The advent of 3D printers has helped the creation of more realistic spinal models that better depict the spinal anatomy.12, 14, 22, 24, 25, 26

Patient-specific modeling is important because each individual has a unique anatomic structure. Precise preoperative planning as optimal entry point, trajectory, screw length, safety zones, anatomic variability of the C1 lateral mass, and VA courses and careful intraoperative guidance is required during screw insertion. In this study, we aimed to describe the application of life-size 3D models prior to surgery of the patients with C1 transarticular screw fixation. The purpose of this study was to evaluate the cervical fracture of patients with 3D models and the functional outcomes of these fractures treated with screw fixation.

Section snippets

Patients

The study included 10 eligible patients who presented to the hospital with complaints of severe arm pain, weakness in arm, and numbness caused by different motor vehicle accidents (motorcycle or car). The patients with C1 spinal fracture who had undergone screw placement surgery between January and November 2016 were retrospectively reviewed from a prospective observational database (Figures 1A and B).

The patients (age range, 15–35 years; men: n = 5; women: n = 5) were treated with posterior

Results

The 3D printing technique aided in forming life-size models that assisted the surgeon to observe the anatomy from any direction. The models were studied in observing and measuring thoroughly. The region surrounding the cervical vertebral joint contains complex structures. Bony elements, such as the spinal canal diameter, transverse foramen diameter, and distance from the midline to the transverse foramen, and the height and area of pedicles were measured, and the data are shown in Table 1. In

Discussion

Screw insertion in the cervical area poses serious challenge to the surgeon because of the variable courses of the VA, the curve of the vertebrae, and the size variability of the small pedicles.1, 10, 17, 27 Misplaced screws, neurologic complications, VA insufficiency, autograft harvest site morbidity, cerebrospinal fluid leak, and wound infections are among common complications.7, 12, 16 The risks of VA insufficiency and neurologic deficit have been cited to be approximately 4.1% and 0.2%,

Conclusions

The proximity of important osteovascular structures in the C1 spine area makes screwing surgery a challenging procedure. Screw malposition is common and emphasizes the need for extensive knowledge of cervical spine anatomy. Iatrogenic vascular injury during C1 spine fixation is linked with increased mortality and neurologic morbidity. With the evaluation of sequential CT slices, a 3D model supports the surgeon project fracture patterns in more details, anticipates intraoperative drawbacks, and

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: Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Original ArticleCreation of 3-Dimensional Life Size: Patient-Specific C1 Fracture Models for Screw Fixation

Highlights

Background

Methods

Results

Conclusions

Introduction

Section snippets

Patients

Results

Discussion

Conclusions

World Neurosurg

Clin Neurol Neurosurg

Spine J

World Neurosurg

Clin Neurol Neurosurg

J Clin Neurosci

Surgery

World Neurosurg

Posterior occipitocervical reconstruction using cervical pedicle screws and plate-rod systems

Spine

Internal reduction established by occiput-C2 pedicle polyaxial screw stabilization in pediatric atlantoaxial rotatory fixation

Pediatr Neurosurg

Anatomic determination of optimal entry point and direction for C1 lateral mass screw placement

J Spinal Disord Tech

Clinical use of 3D printing guide plate in posterior lumbar pedicle screw fixation

Med Sci Monit

Anatomical determination of a safe entry point for occipital condyle screw using three-dimensional landmarks

Eur Spine J

Application of a 3D custom printed patient specific spinal implant for C1/2 arthrodesis

J Spine Surg

En bloc resection of primary malignant bone tumor in the cervical spine based on 3-dimensional printing technology

Orthop Surg

Reconstruction of the upper cervical spine using a personalized 3D-printed vertebral body in an adolescent with Ewing sarcoma

Spine (Phila Pa 1976)

Ideal screw entry point and projection angles for posterior lateral mass fixation of the atlas: an anatomical study

Eur Spine J

Original Article
Creation of 3-Dimensional Life Size: Patient-Specific C1 Fracture Models for Screw Fixation