Technical report of Le Fort I osteotomy using

Microsoft® HoloLens and 3D devicesKiyohiro Kasahara1, Keisuke Sugahara 1,2, Masahide Koyachi1,Yu Koyama1, Mayu Shin1,

Kento Odaka3, Satoru Matsunaga2,4, Shinichi Abe4, Akira Katakura1,2

1 Department of Oral Pathobiological Science and Surgery, Tokyo Dental College

2 Oral Health Science Center, Tokyo Dental College

3 Department of Oral and Maxillofacial Radiology, Tokyo Dental College

4 Department of Anatomy, Tokyo Dental College

In the image-assisted surgery in the conventional Le Fort Ⅰ osteotomy, there are few reports to confirm three-dimensionally

whether the maxilla could be moved as planned during the surgery. In recent years, it has been reported in various fields that

the introduction of Microsoft® HoloLens, which is a head mounted display equipped with Mixed Reality (MR) technology,

during surgery improves the safety and accuracy of surgery and shortens the surgery time. We have reported a method to

confirm the reproducibility of the three-dimensional position of the maxilla during surgery by combining MR and CAD /

CAM techniques for Le Fort I osteotomy. In the present study, we verified the accuracy of reproducibility.

OBJECTIVE

MATERIALS AND METHODS

RESULTS

DISCUSSION AND CONCLUSIONS

Fig.4 ICP evaluation (GOM Inspect)

The right side scale bar means that green area indicate high

accuracy, red and blue area indicate low accuracy. Overlap

errors using a threshold smaller than 2 mm were evaluated and

the frequency of such errors was used as a measure of accuracy.

The accuracy range was 80% to 95%, average 88.3%.

Disclosure of Conflict of InterestName of first author： Kiyohiro Kasahara

I have no COI with regard to our presentation.

AcknowledgementWe thank Holoeyes Inc for

the Mixed Reality technical support.

① ② ③ ⑥④ ⑤

Acquisition image Treatment

planningFabrication of

3D devices

Microsoft🄬HoloLens

applicationOperation Outcome

evaluation

• Surgical splint

• Osteotomy guide

• Repositioning guide

• Registration marker

• The Comparison

between virtual

operation and

postoperative CT.

• Create Microsoft🄬

HoloLens application• CAD/CAM assisted

surgery

• Mixed Reality assisted

surgery

• STL converting

• Virtual operation

• CAD design

• CT

• Cast model scan

Fig.3

（d）Applications of Microsoft® HoloLens are created

from preoperative virtual operation data. Holograms can

depict angiographic areas. It allows the operator to view

blood vessels and areas at risk. HoloLens recognizes the

registration marker so that the hologram and the patient

overlap with the marker.

（e）Operators wearing HoloLens can share the hologram

and can manipulate using gestures and voice.

HoloLens can recognize registration marker.

Microsoft® HoloLens

d

e

A total of 6 patients who underwent either BSSRO and of Le Fort I

osteotomy between January 2019 and April 2019 were included in

this study. One male and six females, with an average age of 25.9.

Preoperative virtual operation and postoperative 1 month CT

superposition were performed semi-automatically with reference to

the cranial bone which did not change in surgery.

Table.1

Unity 2017.4.17f1

Visual Studio Community

2017/Version 15.9.4

OpenCV 3.1 + ArUco

Fig.1

In general, image guided surgery requires expensive equipment, and there have been past reports that patient specific implants, on

average, cost about $ 830 per case. In this method, expensive equipment was not required, and it was possible to make 3D devices at an

average cost of about $ 90 per case.

The accuracy of Le Fort I osteotomy combined with image guided surgery or patient specific implant has been reported that the error

average is 83.8% -97.6%, suggesting the effectiveness of this method.

In the future, we expect that hardware development will further improve the accuracy and safety of surgery.

Fig.2

bSurgical splint Osteotomy guide Repositioning guide

（a）CAD design were done using Materialise ® Mimics and 3-matic.

（b）Surgical splint has junction for osteotomy guide and repositioning

guide on upper side and junction for registration marker on lower side.

（c）e-1 shows the osteotomy guide attached.

e-2 shows the repositioning guide attached.

Intraoperative view

3D Devices

a

c

1 2

Case

Registration maker