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

OBJECTIVE: The craniovertebral junction (CVJ) is unique in the spinal column regarding the degree of multiplanar mobility allowed by its bony articulations. A network of ligamentous attachments provides stability to this junction. Although ligamentous injury can be inferred on CT scans through the utilization of craniometric measurements, the disruption of these ligaments can only be visualized directly with MRI. Here, the authors review the current literature on MRI evaluation of the CVJ following trauma and present several illustrative cases to highlight the utility and limitations of craniometric measures in the context of ligamentous injury at the CVJ.
METHODS: A retrospective case review was conducted to identify patients with cervical spine trauma who underwent cervical MRI and subsequently required occipitocervical or atlantoaxial fusion. Craniometric measurements were performed on the CT images in these cases. An extensive PubMed/MEDLINE literature search was conducted to identify publications regarding the use of MRI in the evaluation of patients with CVJ trauma.
RESULTS: The authors identified 8 cases in which cervical MRI was performed prior to operative stabilization of the CVJ. Craniometric measures did not reliably rule out ligamentous injury, and there was significant heterogeneity in the reliability of different craniometric measurements. A review of the literature revealed several case series and descriptive studies addressing MRI in CVJ trauma. Three papers reported the inadequacy of the historical Traynelis system for identifying atlantooccipital dislocation and presented 3 alternative classification schemes with emphasis on MRI findings.
CONCLUSIONS: Recognition of ligamentous instability at the CVJ is critical in directing clinical decision making regarding surgical stabilization. Craniometric measures appear unreliable, and CT alone is unable to provide direct visualization of ligamentous injury. Therefore, while the decision to obtain MR images in CVJ trauma is largely based on clinical judgment with craniometric measures used as an adjunct, a high degree of suspicion is warranted in the care of these patients as a missed ligamentous injury can have devastating consequences.