Table 3.

Variation in the type of surgical plan, virtual splints and the methodology of accuracy assessment in the included studies

Author, year and country of origin	Surgical planning	Surgical splint	Surgical splint
De Rio et al. 2017 Italy [35]	Bimaxillary surgery	Digital intermediate splints to guide osteotomies.	linear and angular differences to record the vector differences. Wilcoxon signed-rank test and the Mann-Whitney U test were used to analyze the differences between subgroups of the population
Ritto et al. 2017 Brazil [36]	Bimaxillary surgery	An intermediate splint was fabricated virtually	The mean linear difference between the planned movement and the movement obtained for each reference point was calculated, Intraclass correlation coefficient was used for the statistical analysis. The difference in precision between (2D,3D) methods was determined by t-test for independent samples.
Ho et al. 2017 Taiwan [1]	Bimaxillary surgery	Single occlusal splint	Linear and angular distance between reference points on the x (pitch), y roll), and z (yaw) planes
Chin et al. 2017 Germany [37]	9: bimaxillary surgery 1: repositioning of the lower jaw.	Two surgical splints: The first splint would guide the repositioning of segmented maxilla The second one is the final position of lower jaw.	linear and angular measurements were calculated and compared by using a paired t test
Stokbro et al. 2016 USA [38]	Bimaxillary surgery, Bimaxillary surgery with segmentation of the maxilla, Bimaxillary surgery with genioplasty, Bimaxillary surgery with segmentation of the maxilla and genioplasty	Surgical splints and surgical calipers.	The mean linear differences between the virtual plan and the postoperative outcomes were calculated and compared using Wilcoxon signed-rank test with 95% confidence intervals, Mann Whitney and U-test were used to analyze differences between the dependent groups. The clinical success criterion was set at a difference of less than 2 mm
Baan et al. 2016 Netherlands [39]	Bimaxillary surgery	Inter-occlusal wafer was milled based on the virtual planning.	Intraclass correlation coefficient (ICC) was calculated to evaluate the interobserver and intra-observer variability for the rotational and translational measurements of the maxilla and mandible.
Zhang et al. 2016 China [40]	LeFort I osteotomy of the maxilla combined with bilateral SSRO of the mandible. Genioplasty was performed, if indicated (17 patients)	Series of surgical templates: final occlusal splint, two pairs of 3D arms and a pair of bone attachments with indication of osteotomy line	Linear and angular differences between simulated and postoperative models were calculated and statically analyzed using Paired t test .
De Rio et al. 2014 Italy [41]	Clinical and 3D analysis Bimaxillary surgery (20), planning through maxilla (NA) and mandible (NA)	Occlusal splint	Linear and angular distance between the reference points and the reference lines in relation to FHP, CP, MFP, and the frontal process of the zygomatic bone 3D imaging (voxel-based)
Hsu et al. 2013 USA [6]	Bimaxillary surgery planning through maxilla	Occlusal splint, Bone splint (chin)	Calculating linear and angular differences, Bland and Altman’s statistical method
Sun et al. 2013 Belgium [7]	Bimaxillary surgery planning through maxilla	Occlusal splint	Linear and angular distance between reference points on the x (pitch), y (roll), and z (yaw) planes, 3D imaging (surface-best-fit),3ds Max (Autodesk Inc., USA)
Zinser et al. 2013 Germany [42]	Clinical and 3D analysis Bimaxillary surgery (28), planning through maxilla	Occlusal splint, Bone splint (maxilla and mandibular condyle)	Linear distance between the reference points for the x, y, and z planes in 3D imaging (voxel-based)
Centenero and Hernández-Alfaro .2012, Spain [43]	(15) Bimaxillary surgery, (1) Single maxillary surgery	Occlusal splint	Intra-class correlation coefficient (ICC) of the reference lines and angles; concordance level 3D imaging (NA)

3D three-dimensional, NA no information provided by the authors, FHP Frankfort horizontal plane, CP coronal plane, MFP midfacial plane, N nasion point