Journal of Pediatric Neurosciences
EDITORIAL
Year
: 2021  |  Volume : 16  |  Issue : 3  |  Page : 175--181

Anomalous craniovertebral junction (CVJ) anomalies in pediatric population: Impact of digital three-dimensional animated models in enhancing the surgical decision-making


Jayesh Sardhara, Suyash Singh, Arun Kumar Srivastava, Sanjay Behari 
 Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow (UP), India

Correspondence Address:
Dr. Jayesh Sardhara
Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow (UP).
India




How to cite this article:
Sardhara J, Singh S, Srivastava AK, Behari S. Anomalous craniovertebral junction (CVJ) anomalies in pediatric population: Impact of digital three-dimensional animated models in enhancing the surgical decision-making.J Pediatr Neurosci 2021;16:175-181


How to cite this URL:
Sardhara J, Singh S, Srivastava AK, Behari S. Anomalous craniovertebral junction (CVJ) anomalies in pediatric population: Impact of digital three-dimensional animated models in enhancing the surgical decision-making. J Pediatr Neurosci [serial online] 2021 [cited 2022 Jul 5 ];16:175-181
Available from: https://www.pediatricneurosciences.com/text.asp?2021/16/3/175/321798


Full Text



The challenges and complexity in the management of pediatric craniovertebral junction (CVJ) anomalies lie in the difficulty of precisely diagnosed the CVJ instability in this age group, followed by strategizing the fusion method. Three aspects are essential to incorporate in the management algorithm of pediatric CVJ anomalies. The first is developmental, consisting of separation and resegmentation of the spinal column at the CVJ which requires that the age-dependent ossification process of the cartilaginous part of C1 and C2 be understood to enable an accurate diagnosis based on computed tomography (CT) and magnetic resonance imaging (MRI), especially in infants and children less than 6 years old; second, because the CVJ is the most mobile part of the spinal column, assessment of the functional anatomy via CT/MRI-based dynamic motion studies is often critical to revealing the pathogenesis of CVJ lesions. The third aspect is the understanding of the bony anatomy of the CVJ is a crucial prerequisite to optimal planning of surgery. These intricate anatomical understanding may be simplified by using preoperative 3D digital animated models.

The clinical application of visual three-dimensional (3D) software animations is rising in the medical field in the recent era.[1],[2],[3],[4],[5],[6] Access to cadaveric laboratories is limited nowadays. Therefore, the virtual software offers a cost-effective educational resource. The editorial provides proof of the concept that how the utilization of simple software application for 3D visualization in the preoperative period during surgical management of pediatric CVJ anomalies can turn the highly intricate CVJ pathology to a simpler one by helping to understand the biomechanics and developmental anatomy. It became a trend changer in the surgical filed of CVJ. The unique advantages of reusability, multi-angle specimen observation, and nondestructive virtual anatomy give an edge to digital 3D animated model technology.

 Digital 3D Animated Model: An Advance Education Tool



It is imperative to master the aberrant anatomy of CVJ in case of developmental or syndromic anomaly.[7],[8],[9] The ability to conceptualize and anticipate the preoperative radiological findings in the 3D hypothetical image, usually comes by experience. This capability or potential is different among the surgeons and necessitate a learning curve. The learning curve of each surgeon is unrelated and depends on several factors. However, with the introduction of 3D simulation models like 3D printing, saw-bone models, and new digital 3D models, one may curtail his learning curve and also offer better and safe surgical outcomes. Among these three, the digital 3D model is cheapest, widely available, reproducible, and most accessible to depict the slightest variation from normal anatomy. These 3D computer-based software models enable the surgeon to rotate virtual vertebral bodies and understand the spatial relationships. The new versions of Macintosh Operating System (IOS) have in-built software in Powerpoint/Office programs compatible with magnetic resonance imaging (MRI) viewer. Using this software, one has to upload the MRI or computed tomography (CT) scan of the patient and generate a virtual image. The software can not only measure the size of pedicles, a distance of vertebral artery from affix, or standard screw entry points, but the visualization tools may also be used for scrolling or zoom-in-out the image.

Therefore, the interpretation of complex CVJ anatomy and safe screw trajectory in the background of the anomalous vertebral artery course converts much easier for surgical planning. The models are also an excellent method for teaching purposes, being easily reproducible and has a wide projection. The standard cadaver system of teaching is expensive and challenging to translate on a pediatric patient of CVJ anomaly. Goel et al. showed that the digital 3D software models stipulate a dynamic display of multiple orientations.[3] Nguyen et al. also showed that learning human anatomy is influenced by the interaction between the learner’s spatial ability and the dynamism and interactivity of the instructional tool.[5] Therefore, a simple 3D software tool delivers a worthy opportunity for young surgeons in their initial learning curve period.

 Conceptualization of 3D C1–C2 Dislocations by 3D Model



One must conceptualize the dislocation in three dimensions and understand the pathological biomechanics in all the three planes. Our prior publication describes six types of dislocations, most common one is the combined type of C1–C2 dislocation in all three axes; i.e., the amalgamation of translational dislocation [increase in atlanto-dental interval (ADI) >4.5 mm in pediatric age]; presence of basilar invagination; and coronal tilt and rotational dislocation altogether.[10] The digital 3D animated models exactly postulate this information and enlighten the surgeon in the better surgical decision. The capability to rotate the animated model, highlight the anomalous anatomy, and measure the vertebral part’s width assists the neurosurgeon. Some of the case illustrations are described with various types of C1–C2 dislocation, which is planned by the help of a 3D animated model for optimal correction [Figure 1][Figure 2][Figure 3][Figure 4][Figure 5][Figure 6][Figure 7].{Figure 1} {Figure 2} {Figure 3} {Figure 4} {Figure 5} {Figure 6} {Figure 7}

 Clinical Application of Novel Digital 3D Models in Pediatric Neurosurgery Practice



Precisely pinpointing the developmental stage of CVJ

Developmental anatomy demonstrates age-dependent mechanisms and the pathophysiology of pediatric CVJ anomalies.[11] At a younger age, the atlantoaxial instability is mostly reducible. Menezes describes the sequence of events, in the process of progressive vertical dislocation of facet joints in the posterior fossa, pannus forms around the odontoid process, till this age, C1–C2 instability (the process of odontoid invagination into the foramen magnum) is still reducible but progressive. However, as the child grows, grooving occurs behind the occipital condyles secondary to upward migration of the axis vertebra, which makes it irreducible at 14 to 15 years of age. Moreover, the protective cervical muscle muscles are relaxed or inadequately developed, as, in the case of a young child under general anesthesia, the craniovertebral junction becomes inherently less stable than that in an adult.[12] Thus, before 14 years of age, traction will help to reduce the majority of irreducible AAD and BI due to the laxity of ligaments of CVJ and muscle relaxant effect with general anesthesia. Dynamic 3D reconstruction helps in to recognize the factors responsible for irreducibility like supernumerary facet joints, asymmetrical facet joints, and very high BI with rotational dislocation.

Morphological analysis of C1 lamina suggested that the diameter of C1 lamina reached approximately 4 mm by 4 to 6 years of age.[13] Likewise, the width of the pedicle and lateral mass of C2 becomes more then 5 mm after 2 years of age, in that case, the use of a 3.5-mm lateral mass and pedicle screw in 2- to 6-year-old children was feasible in the majority of cases but with caution to prevent the inadvertent entry into vertebral artery groove in a patient with anomalous C2 lateral mass hypoplasia or narrow isthmus.[14] During the developmental stage in the ossification process, by synchondrosis of C1 and C2 arch, both the side of arches fused in the midline and become 5 mm in width at 6–7 years of age. That is why we prefer to apply a horizontal connector between two side rods to provide maximum stability, especially in the rotational movement of the cervical vertebra. Thus, the 3D model helps into the assessment of the development of lamina, lateral mass as well as pedicle width to preoperatively plan the need for a particular screw size and surgical method of fusion technique.

The Bony fragility and maturity are variable with the ossification stages of CVJ. In developing age, the ossification of the cartilaginous part of CVJ was completed at around 5 to 7 years of age. Before 7 years of age, any CVJ instability, whether it should be considered as occipito-cervical instability or only C1–C2 instability, is quite dubious. We consider it occipito-cervical instability and prefer occipito-cervical fusion rather than only C1–C2 fusion below 5 years of age. Another typical indication of occipito-cervical fusion is AAD, BI, with occipitalization of Atlas where very high BI, anomalous C1 lateral mass anatomy, and anomalous course of VA crossing the C1–C2 joints preclude the C1 lateral mass fixation. In such a case, occipito-C2/C3 fixation after distraction would help to prevent vertebral artery injury; moreover, as C1 is occipitalized, the biomechanics does not affect whether you do C1/2 or occipito-C2 fixation. The 3D model’s assistance meticulously evaluates not only the facet joints’ symmetricity but also the vertebral artery anomalies and course related to C1/C2 joints. Thus, the preoperative selection of the C1/C2 fixation vs occipito-cervical fixation can be determined.

Understanding the vertebral artery anomalies related to C1/C2 joints

The 3D animated model helps define the precise bony and VA variations that may be responsible for heightened intraoperative risk. We have classified the vertebral artery congenital variations in the third part of CVJ and established the scoring system based on various vertebral artery anomalies and its implications to prevent the VA injury during C1/C2 screw fixation.[15] It helps to choose the appropriate surgical technique of posterior stabilization based on the preoperative location of VA relative to the C1–C2 facet joints.[15] The anatomical variations include the presence of a persistent first intersegmental artery, a fenestrated VA, or a low-lying PICA: An anomalous medial deviation of the third segment of VA; a high-riding VA with a narrow C2 isthmus; a rotational deformity or a tilt at the occipital-C1–C2 level that again resulted in a medial deviation of VA; and unilateral dominance of VA. The intracranial course of the VA, especially in the third part, can be precisely defined via the preoperative 3D animated model [Figure 7]. Objective risk stratification of the VA helps in significantly reducing its chances of injury during pediatric CVJ surgery.[15]

 Conclusion



The advent of highly advanced radiological investigational tools like the 3D animated model embarks the new revolution in pediatric CVJ surgery. Translating a CVJ anomaly in the three-dimensional virtual image is an art, which comes by experience. The understanding of 3D congenital C1/C2 facet joint dislocation, symmetricity of the joints, and precise developmental age helps in the correct diagnosis of CVJ instability in pediatric age. It helps in optimal and safe surgical correction of the instability by accurate planning.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Patel CR, Maleki A, Kulkarni S Enhancing the learning experience of embryology for medical students. Adv Med Educ Pract 2018;9:139-41.
2Park S, Kim Y, Park S, Shin JA The impacts of three-dimensional anatomical atlas on learning anatomy. Anat Cell Biol 2019;52:76-81.
3Goel A, Jankharia B, Shah A, Sathe P Three-dimensional models: An emerging investigational revolution for craniovertebral junction surgery. J Neurosurg Spine 2016;25:740-4.
4Hoyek N, Collet C, Di Rienzo F, De Almeida M, Guillot A Effectiveness of three-dimensional digital animation in teaching human anatomy in an authentic classroom context. Anat Sci Educ 2014;7:430-7.
5Nguyen N, Nelson AJ, Wilson TD Computer visualizations: Factors that influence spatial anatomy comprehension. Anat Sci Educ 2012;5:98-108.
6Garg AX, Norman GR, Eva KW, Spero L, Sharan S Is there any real virtue of virtual reality? The minor role of multiple orientations in learning anatomy from computers. Acad Med 2002;77:97-9.
7Behari S, Bhargava V, Nayak S, Kiran Kumar MV, Banerji D, Chhabra DK, et al. Congenital reducible atlantoaxial dislocation: Classification and surgical considerations. Acta Neurochir (Wien) 2002;144:1165-77.
8Sardhara J, Behari S, Jaiswal AK, Srivastava A, Sahu RN, Mehrotra A, et al. Syndromic versus nonsyndromic atlantoaxial dislocation: Do clinico-radiological differences have a bearing on management? Acta Neurochir (Wien) 2013;155:1157-67.
9Salunke P, Behari S, Kirankumar MV, Sharma MS, Jaiswal AK, Jain VK Pediatric congenital atlantoaxial dislocation: Differences between the irreducible and reducible varieties. J Neurosurg 2006;104:115-22.
10Sardhara J, Behari S, Sindgikar P, Srivastava AK, Mehrotra A, Das KK, et al. Evaluating atlantoaxial dislocation based on cartesian coordinates: Proposing a new definition and its impact on assessment of congenital torticollis. Neurosurgery 2018;82:525-40.
11Salunke P Congenital atlantoaxial dislocation: Nature’s engineering gone wrong and surgeon’s attempt to rectify it. J Pediatr Neurosci 2018;13:1-7.
12Menezes AH Craniocervical developmental anatomy and its implications. Childs Nerv Syst 2008;24:1109-22.
13Morota N Pediatric craniovertebral junction surgery. Neurol Med Chir (Tokyo) 2017;57:435-60.
14Fan D, Song R, Zhang M, Bai R, Li Y, Zhang Z, et al. Guideline for C1 lateral mass and C2 pedicle screw choices in children younger than 6 years. Spine (Phila Pa 1976) 2017;42:E949-55.
15Sardhara J, Behari S, Mohan BM, Jaiswal AK, Sahu RN, Srivastava A, et al. Risk stratification of vertebral artery vulnerability during surgery for congenital atlanto-axial dislocation with or without an occipitalized atlas. Neurol India2015;63:382-91.