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