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

Abstract

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.

Keywords: 3D printed model; Atlantoaxial dislocation; Basilar invagination; C1–C2; Craniovertebral junction abnormality; Occiput–C2.

Figure 1:

(a) Posterior view of a three-dimensional printed model of a patient, (b) lateral view of the model, (c) anterior view of the model showing fused left lateral mass of C1 with occipital condyle (solid red arrow), and (d) practice on model with occipital-C2 plate and screws.

Figure 2:

Modified Japanese orthopaedic association score (m JOA), the maximum score is 18.

Figure 3:

(a) Comparison of preoperative and postoperative m JOA score in study group and (b) Comparison of preoperative and postoperative m JOA score in control group.

Figure 4:

(a) Comparision of recovery rates among study and control group, (b) mean change in atlanto-dental interval in study (3.94) versus control group (3.15), (c) mean change in canal line in study (4.2) versus control group (2.76), and (d) mean change in wackhenheims clivus canal line in study (4.55) versus control group (3.26).

Figure 5:

Uncommon case of absent C2 posterior elements with C2-C3 spondyloptosis; (a) preoperative computed tomography (CT) scan (MidSagittal cut) showing absent C2 lamina (hollow arrow), C2-C3 spondyloptosis (asterix), hypertrophied spinous process of C3 (solid arrow), and C5-C6 block vertebra (diamond), (b) magnetic resonance imaging T2W image, midsagittal section showing severe cord compression by retropulsed C3 body, (c) 3D model of the craniovertebral junction of the patient showing posterior view with absent C2 lamina, well developed uncinate process of C3 (hollow arrow), and hypertrophied spinous process of C3 (solid arrow), (d) showing hands on practise on the model preoperatively, (e and f) comparison between the preoperative and postoperative CT scan (Mid Saggital view) of the patient showing acceptable reduction and realignment of the C2-C3 body with increased canal diameter at the level of C3 and iliac bone graft between C1 posterior arch and C3 spinous process in situ (solid arrow). The model helped us in better understanding of the complex anatomy and planning preoperatively, and (g and h) C1 lateral mass and C2 pedicle screw insertion.