(45) Evaluation of the Accuracy of In-House Virtual Surgical Planning for Orthognathic Surgery

Abstract: Virtual Surgical Planning (VSP) has become the standard for orthognathic surgery and is largely performed by outsourced (OS) companies.¹ However, the validation of in-house (IH) VSP and splint manufacturing in the literature remains insufficient, despite its potential benefits. The purpose of this study was to evaluate the accuracy and cost of mandibular surgery using IH processing compared to OS methods.

This is an in-vivo retrospective study of orthognathic cases performed by Virginia Commonwealth University Department of Oral and Maxillofacial Surgery. Methodology was scientifically validated prior to this study. The primary outcome variable was the accuracy of the planned post op occlusion compared to the IH VSP, utilizing whole-surface analysis to obtain a root mean square (RMS) value. Secondary outcome variable was the cost of manufacturing the splints. The predictor variables were IH versus OH splint. Inclusion criteria included individuals with skeletofacial deformities requiring bilateral sagittal split osteotomies (BSSOs) only. Exclusion criteria included any patients requiring concomitant LeFort or TMJ surgeries.

The surgical team conducted in-house (IH) VSP using Materialise Mimics CMF Enlight (Materialise NV., Leuven, Belgium), and the final splint was 3D-printed on a Formlabs 3B+ with surgical guide resin. In contrast, outsourced (OS) VSP and splints were provided by an external company. Post-operative (PO) CBCT was obtained two weeks after surgery and was superimposed on the original VSP file on Materialise 3-matic (Materialise NV., Leuven, Belgium).

Two one-sided t-tests approach was used to determine the equivalence bounds at 0.05 level between the results of the control group (OS) and experimental group (IH). 15 patients were included in the study (5 per IH, 10 per OH). The average RMS for the IH group was 1.199 while the average RMS for OH group was 1.187. Cost per print for IH was $10 versus OS $1,800.

The RMS for the two methods is equivalent within ± 2 mm, which is the current clinically acceptable standard² at the .05 level. The 90% CL indicates they are equivalent within -0.22, 0.20, with OS VSP measuring an average of .02 larger in terms of RMS.

IH designing and manufacturing of splints demonstrated equivalent success as compared OS products for BSSOs. This may provide a path for more utilization of IH processes for orthognathic surgery. IH has less cost than OS. More studies are needed to test application of IH VSP as it relates to time and cost savings.

Literature Cited:

1. Farrell BB, Franco PB, Tucker MR. Virtual surgical planning in orthognathic surgery. Oral Maxillofac Surg Clin North Am. 2014 Nov;26(4):459-73. doi: 10.1016/j.coms.2014.08.011. Epub 2014 Sep 22. PMID: 25246324
2. Alkhayer A, Piffkó J, Lippold C, Segatto E. Accuracy of virtual planning in orthognathic surgery: a systematic review. Head Face Med. 2020;16(34). https://doi.org/10.1186/s13005-020-00250-2
Figure 1: IH VSP and splint processing workflow. Top row demonstrating segmentation with planned osteotomies of the mandible. Middle row demonstrating splint design. Bottom row demonstrating planned post-op occlusion.Figure 2: RMS equivalency between IH and OS VSP groupsFigure 3: Cost Breakdown for Splint Fabrication (OS vs. IH)