3D Printing Model of a Patient's Specific Lumbar Vertebra

Summary

This study aims to create a 3D-printed model of a patient-specific lumbar vertebra, which contains both the vertebra and spinal nerve models fused from high-resolution computed tomography (HRCT) and MRI-Dixon data.

Abstract

Selective dorsal rhizotomy (SDR) is a difficult, risky, and sophisticated operation, in which a laminectomy should not only expose an adequate surgical field of view but also protect the patient's spinal nerves from injury. Digital models play an important role in the pre-and intra-operation of SDR, because they can not only make doctors more familiar with the anatomical structure of the surgical site, but also provide precise surgical navigation coordinates for the manipulator. This study aims to create a 3D digital model of a patient-specific lumbar vertebra that can be used for planning, surgical navigation, and training of the SDR operation. The 3D printing model is also manufactured for more effective work during these processes.

Traditional orthopedic digital models rely almost entirely on computed tomography (CT) data, which is less sensitive to soft tissues. Fusion of the bone structure from CT and the neural structure from magnetic resonance imaging (MRI) is the key element for the model reconstruction in this study. The patient's specific 3D digital model is reconstructed for the real appearance of the surgical area and shows the accurate measurement of inter-structural distances and regional segmentation, which can effectively help in the preoperative planning and training of SDR. The transparent bone structure material of the 3D-printed model allows surgeons to clearly distinguish the relative relationship between the spinal nerve and the vertebral plate of the operated segment, enhancing their anatomical understanding and spatial sense of the structure. The advantages of the individualized 3D digital model and its accurate relationship between spinal nerve and bone structures make this method a good choice for preoperative planning of SDR surgery.

Introduction

Spastic cerebral palsy affects over half of all children with cerebral palsy¹, leading to tendon contractures, abnormal skeletal development, and decreased mobility, greatly impacting the quality of life of affected children². As the main surgical method for the treatment of spastic cerebral palsy, selective dorsal rhizotomy (SDR) has been fully validated and recommended by many countries^3,4. However, the intricate and high-risk nature of SDR surgery, including the precise cutting of the lamina, positioning and dissociation of nerve roots, and severing of nerve f....

Protocol

All data come from the clinical patient, whose SDR operation was carried out at BJ Dongzhimen Hospital. The protocol follows the guidelines of and was approved by the Dongzhimen Hospital research ethics committee.

NOTE: The whole map of the model reconstruction protocol is shown in Figure 1. The high-resolution computed tomography (HRCT) data and Dixon data are raw materials for modeling; then, the 3D model creation consists of image registration and fusion. The final 3D digital model is printed by PolyJet technology which is a high-precision 3D printing process that produces smooth and accurate parts using a w....

Results

Based on lumbar CT/MRI image fusion data in children with cerebal palsy, we created a representative model of the lumbar spine combined with spinal nerves. High-pass filtering was used to extract the high signal in the CT value range of 190-1,656 from HRCT, so as to achieve the reconstruction of the bone structure of the lumbar spine in the operation area. Spinal nerve structures were reconstructed by the high-pass filtering of Dixon-w sequences in MRI. The digital model and point cloud data coordinates of the lumbar ver.......

Discussion

This study provides a workflow for establishing a preoperative 3D printing model of the lumbar spine in patients with cerebral palsy, with the aim of facilitating preoperative planning for SDR surgery and enhancing anatomical training based on the patient's specific model. The study aims to establish a highly reliable 3D-printed model that accurately demonstrates the patient's lumbar vertebral and nerve structures. By measuring the position of the lamina and spinal nerve in the model before surgery, precise planning of t.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
J55 Prime 3D-Printer	Stratasys	J55 Prime	Manufacturing the model
MATLAB	MathWorks	2022B	Computing and visualization
Mimics	Materialise	Mimics Research V20	Model format transformation
Tools for volum fusion	Intelligent Entropy	VolumeFusion V1.0	Beijing Intelligent Entropy Science & Technology Co Ltd. Modeling for CT/MRI fusion