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150Chapter9Surgery was performed under general anesthesia with nasotracheal intubation Theleftcondyle wasapproached throughapost-tragalincision withalimitedsuperiorpreauricularextensionAftergainingaccesstothecondylarheadthesurgeonidentifiedtheplaneofcondylectomyvisuallyThreemarkingpointswereplaceonthelateralcondylarsurfacewitharoundburrBywearingMicrosoftHoloLens(MicrosoftWashingtonUSA)thepositionofthreemarkingswascheckedusingthefollowingsteps1Asterilequickresponse(QR)markerwasattachedtothelowerdentitiontoallowtrackingofthemandibularpositionthroughtheHoloLens2Astainless-steelpointer,equippedwithasecondQRmarker,wasusedtocheckthelocationoftheplannedosteotomyline(Figure1)3Aninhouse-developedHoloLensapplicationenabledthesurgeonto visualize theplannedpositionof theosteotomylineand the threemarkingsTheHoloLensdisplayedavirtualarrowatthelocationofthepointer todirect thesurgeon tomove thepointer to theplannedposition(Figure2)Nexttheactualcondylectomywasperformedwitharoundburrbasedonthemarkings ThecranialpartofthecondylarheadwasremovedFivedaysfollowingsurgeryapostoperativecheck-upCBCTwasacquiredTheplannedandactuallocationofthecondylectomyplaneswerecomparedRESULTSANDDISCUSSIONThe3Dregistrationofplannedandpostoperativemandibularmodels(Figure3)showedthatonthelateralanteriorandmedialsideofthecondylethecondylectomywasperformedalmostexactlyaswasplanned(error≤1mm)However,thepostoperativeposteriorborderoftheleftcondylewaslocatedmorecaudallycomparedtotheplanning ThisdiscrepancycouldbearesultofthefactthatonlythelateralpositionoftheosteotomywasverifiedbytheHoloLens
