GP2d - Patient-Specific Plates Are More Accurate Than Traditional Plates for Le Fort I Advancement > 7 mm

Abstract: Patient-specific plates (PSPs) are prefabricated to the desired final orthognathic position as determined by virtual treatment planning. This plating system comes with additional costs with potential benefits such as accuracy and intraoperative time saving. We aimed to determine if the cost is justified by more accurate outcomes over the traditional plating system by utilizing a user-independent superimposition method to assess pre- and postoperative movements following Le Fort I (LFI) repositioning. We hypothesized that the accuracy of PSPs justifies the additional expense.

Voxel-superimposed cone-beam computer tomography (CBCT) scans were used to determine the actual versus predicted vertical and horizontal maxillary movements after LFI osteotomy when utilizing PSPs vs. traditional plates (TPs).

The study involved a retrospective chart review of 30 patients who underwent a LFI osteotomy by a single surgeon during March 2022 to March 2023. Inclusion criteria were patients whose surgeries were planned virtually and were fixated with either PSPs or TPs. Patients without adequate imaging were excluded. Movements were measured using pre- and postoperative CBCT scans, obtained on postoperative day one. Voxel-superimposition was performed to align the anterior skull base(s) using the software program Geomagic Design X. A single engineer identified the landmarks, A-point (A), anterior nasal spine (ANS), maxillary Incisor (Isu1), left maxillary first molar (U6L), and right maxillary first molar (U6R). Landmarks were selected to assess movement in the AP and vertical directions. A method error was calculated by requiring the engineer to re-identify the specific landmarks on three separate occasions, assessing for accuracy. Pearson correlation was used to assess the accuracy in identifying landmarks by the engineer, with coefficients >0.9-1 on each of the three occasions. The primary outcome variable was the difference between the predicted and actual movements ( < 7 mm) in the anterior-posterior (AP) direction and > 5 mm movements vertical to any of the landmarks. Wilcoxon rank-sum tests were used to compare the differences in medians between the 2 types of plating for the AP and vertical differences in actual and predicted values.

Of the 30 patients reviewed, 16 (53%) received PSPs and 14 (47%) TPs. Twenty-four (80%) patients were either female, greater than 18 years of age, or non-cleft patients. Eighteen (60%) underwent bimaxillary surgery. Nineteen (63%) underwent movements > 7 mm in the AP direction.

When pre- and postoperative CBCT scans were overlaid with voxel-superimposition, PSPs were found to be more accurate than TPs with movements >7 mm in the AP direction. Further analysis suggested greater accuracy with PSP for the cleft population compared to TPs. No significant differences were found between PSPs and TPs regarding accuracy in the vertical direction. PSPs were more accurate than TPs at A point when movements were > 7 mm (P = .04). Otherwise, the accuracy between the two plating systems is comparable. The hypothesis is accepted for those undergoing >7 mm of maxillary advancement at the LFI level, but the expense is considerable.<

References
1. Haas Junior OL, Guijarro-Martínez R, Sousa Gil AP, Méndez-Manjón I, Valls-Otañón A, de Oliveira RB, Hernández-Alfaro F. Cranial Base Superimposition of Cone-Beam Computed Tomography Images: A Voxel-Based Protocol Validation. J Craniofac Surg. 2019 Sep;30(6):1809-1814. doi: 10.1097/SCS.0000000000005503. PMID: 31033755.

2.Andriola FO, Haas Junior OL, Guijarro-Martínez R, Hernández-Alfaro F, Oliveira RB, Pagnoncelli RM, Swennen GR. Computed tomography imaging superimposition protocols to assess outcomes in orthognathic surgery: a systematic review with comprehensive recommendations. Dentomaxillofac Radiol. 2022 Mar 1;51(3):20210340. doi: 10.1259/dmfr.20210340. Epub 2021 Sep 14. PMID: 34520241; PMCID: PMC8925870.