Accuracy of orthognathic surgical outcomes using 2d and 3d landmarks – the case for apples and oranges?

Publication date: Available online 12 January 2018
Source:Journal of Oral and Maxillofacial Surgery
Author(s): Alexandre Meireles Borba, Everton José da Silva, André Luis Fernandes da Silva, Michael D. Han, Maria da Graça Naclério-Homem, Michael Miloro
PurposeTo verify predicted versus obtained surgical movements in 2D and 3D measurements and compare the equivalence between these methods.MethodsA retrospective observational study of bimaxillary orthognathic surgeries was performed. Postoperative CBCT scans were superimposed to preoperative scans, and a lateral cephalometric radiograph was generated from each CBCT. After identification of landmarks Sella, Nasion and upper central incisor tip on 2D and 3D images, actual to planned movements were compared on cephalometric measurements. One sample t-test was used to statistically evaluate results to expected means varying from 0 to 2 mm of discrepancy. Equivalence from 2D and 3D values were compared using a paired t test.ResultsFinal sample of 46 cases demonstrated on 2D cephalometry that the differences between actual versus planned movements on the horizontal axis were statistically significant for expected means of 0, 0.5 and 2 mm, and without significance for expected means of 1 and 1.5 mm; vertical movements were statistically significant for expected means of 0 and 0.5 mm, without significance for expected means of 1, 1.5 and 2 mm. For 3D cephalometry on the horizontal axis, there were statistically significant differences for expected means of 0, 1.5 and 2 mm, without significance for expected means of 0.5 and 1 mm; vertical movements showed statistically significant differences for expected means of 0, 0.5, 1.5 and 2 mm, without significance for expected mean of 1 mm. Comparison of 2D and 3D values displayed statistical differences for both horizontal and vertical axes.ConclusionsComparison of 2D and 3D surgical outcomes assessments should be performed with caution since it seems that there is a difference on acceptable levels of accuracy between both methods of evaluation. Moreover, 3D accuracy studies should no longer rely on a 2 mm level discrepancy level but on a 1 mm level.



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