The Microanatomic Research On Temporal Bone And Lateral Transpetrosal Approaches

The Microanatomic Research on Temporal Bone andLateral Transpetrosal ApproachesObjective To study the morphology and inner structures of temporal bone andmeasure space relationship among structures.To compare the effect on operativeprocedure and operative exposure between neuronavigation-aided Kawase approachand conventional Kawase approach.To compare the effect on operative exposureamong retrolabyrinthine approach,PLPA approach and translabyrinthine approach.Methods (1)Vessels perfusion and microanatomy were performed in 15 cadavericheads.Outlines of temporal bone and space relationship between inner structureswere measured.(2)Neuronavigation-aided Kawase approaches were performed onone side of cadaveric heads while conventional Kawase approach were performed onthe other side in 6 cadaveric heads.To analyze the effect of neuronavigation onoperative exposure by comparing areas of drilled Kawase triangle and posterior fossadura,operative angle of vision and the thickness of residual bone on ICA.(3)Retrolabyrinthine approaches,PLPA approaches and translabyrinthine approacheswere performed in other 9 cadaveric heads.To estimate the effect of three differentapproaches on operative exposure by measuring the distance between rear part ofposterior semicircular canal and anterior margin of the sigrnoid sinus at the level oflateral semicircular canal,exposure areas of posterior fossa,operative angle of visionand residual lateral projection area of drilled semicircular canal.Results (1)Morphologic measurement was performed in temporal bones with 5 lines.The space relationship of facial nerve,GSPN,semicircular canal,cochlea and ICAwere researched and found that the angle between GSPN and internal acoustic meatuswas 70°in Chinese specimens.(2)By applying neuronavigation-aided Kawaseapproach,accurate location of inner structures of petrous bone was achieved andoperation duration would reduce by about 20-30 min.The accuracy of navigationsystem is 1.18±0.06 mm,operative angle of vision increased by 3.72°(26.9%),thethickness of residual bone on ICA reduced by 2.23mm.The areas of drilled Kawase triangle increased by 23.45 mm~2 (11.26%)and the areas of posterior fossa increasedby 49.45 mm~2 (29.9%).There is statistically difference betweenneuronavigation-aided Kawase approach and conventional Kawase approach.(3)Thesize of Trautman triangle would affect operative space when performingmastoidectomy.The distance between rear part of posterior semicircular canal andanterior margin of the sigmoid sinus increased by 4.45 mm(57.8%),exposure areas ofposterior fossa dura increased by 157.32 mm~2 (64.3%)and operative angle of visionwas 329.6% that of retrolabyrinthine approach when performing PLPA approachcompared with retrolabyrinthine approach.While compared PLPA approach withtranslabyrinthine approach,the three figures above has less increase.Whileperforming PLPA approach,the lateral projection areas of semicircular canals wasdrilled off by 84.7%,only 15.3% was retained and broad operative channel towardspetroclival region was obtained.Conclusions Temporal bone is the most complicated bone both in structure andfunction and there is great difference among morphologic measurement.The anglebetween GSPN and internal acoustic meatus was 70°in Chinese specimens,whichcan precisely locate internal acoustic meatus.Neuronavigation-aided Kawaseapproach can increase the areas of drilled Kawase triangle and posterior fossa,locatethe inner structures of petrous bone precisely,increase operative angle of vision,reduce the thickness of residual bone on ICA and reduce operation duration.Compared with retrolabyrinthine approach,PLPA approach increases the exposureareas of posterior fossa dura and operative angle of vision.While compared withtranslabyrinthine approach,there is less increase in exposure areas of posterior fossadura and operative angle of vision.PLPA approach can preserve hearing function andobtain good exposure towards petroclival region.It is a considerable ideal approachto treat petroclival lesions.