Surgical planning using virtual reality and remote use of three-dimensional​ surgery simulation

Introduction

Cooperation between orthodontists and oral surgeons is significant for surgical orthodontic treatment, however there are possibilities to occur differences in the realization of the treatment plan due to the lack of smooth proceeding in developing the treatment plans and communicating its modifications.​

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At our clinic, computer graphics are used in Virtual Reality (hereinafter referred to as “VR”) as one of the communication tools　to help analyzing various types of a three-dimensional images and planning and modifying treatment plans.​

Materials and methods

1. Verification of measurement accuracy on VR, monitors and models

Ⅰ) Creation of STO​

DICOM data was obtained by photographing the patient and the patient‘s plaster model mounted on an articulator using a cone-beam CT (hereinafter referred to as CBCT) . Using virtual preoperative planning software for craniomaxillofacial surgery (ProPlan CMF, Materialise, software below: is shown in Photo 1), the STO was created by setting the movement amount and movement direction of the upper and lower jaw bones.​

Then created STL data from them and input it to the medical VR system (Holoeyes XR, HoloEyes), and performed stereoscopic vision and operation with VR goggles (Occulus Quest : is shown in the Photo 2). Furthermore, a 3D printer (ZENITH, Yoshida, Form2, Formlabs: is shown in Photo 3) was used to make a remodel able mock - up (is shown in Photo 4) and a small bone fragment mock-up of the interference part.​

The Picture 1shows the image of the skull on the screen of the software.​

II) Measurement by each devise​

1： Measurement of Minor Segment Interference​

Subjects are four cases of STO created by two jaw surgery (Case A, Case B, Case C and Case D.)​

In order to measure the amount of Set Back in the right side of the mandible and the amount of interference between the right side of the mandible and minor segment, the overlapping area of the minor segment and the mandibular body was extracted (hereinafter referred to as the interference area). The width diameter of the interference area ( measurement ① ) and the long diameter of the buccal aspect （measurement ② ） were measured with reference to the three –dimensional reference plan at the time of STO creation (is shown in Photo 5).​

To measure the width and longitudinal diameters of the actual models by also using calipers. (is shown in Photo 6).

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2: Measurement of the amount of maxillary advancement​

Two cases (Case E and Case G) in which communication on a two-dimensional screen was difficult when discussing the amount of anterior movement of the maxilla (Case E and Case G) were included in the study. On the right side of the maxilla, the amount of advancement (measurement ③) was measured in the area corresponding to the fixed plate running area (is shown in Photos 7and 8)​

In order to measure ① to ③, the distance was measured by pointing at each point that was considered to be approximately the same. Each measurement was made by the same measure and measured 10 times each, and the mean and variance were determined and compared.​

2. Lattice analysis

The reference plane and the grid were set when considering from multiple directions in the VR space.​

The application of reference planes and lattices is useful for pointing landmarks, setting coordinate systems, and recognizing left-right symmetry. (Photo 9)

Mater

Result 1　

Verification of measurement accuracy on VR, monitors and models

3. Use of VR

A substantive model created from the results　of CG – based virtual surgery was used to discuss surgical planning and treatment goals. ​Using STL data to display the materials in VR space.​

A three-dimensional examination of the material in VR space was possible from multiple directions at any magnification rate.​ It was possible to point and move the materials and cut them in any plane in the VR space. ​By synchronizing the view of the VR goggles with the monitor, it is easy to understand the view of others.

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Result 2

​Use of VR

By performing virtual surgery using CG and visualizing it in the VR space, it was possible to study a three-dimensions while referring to the reference line even in a remote discussion.​

Discussion ＆ Conclusions

The reason why the variance in the measurement in VR was small may be due to the fact that the pointing of the measurement was stable in VR as the measurement site was magnified.​

We believe that the use of VR technology and mock-ups made the discussion between oral surgeons and orthodontists easier to understand for both parties.​

Bridging the perception gap between oral surgeons and orthodontists is essential in performing precision jaw deformity surgery.​

Discussions are necessary to bridge the perception gap in perception, and the discussions with appropriate devices are considered useful.​

It is hard to grasp the position and size of the interference of the bone fragments from the conventional data, however it is useful to grasp it by virtual surgery using CG and rendering in a three-dimensional.

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