Study Of Microsurgical Anatomy Of Operative Approach To The Crainocervical Junction Region And Fixation Method

1.Study of microsurgical anatomy of the suboccipital far-lateral approach to theeraniocervical junetion(CCJ)region and posterior fixation methodObjective:To investigate the microanatomical structure in ventral-lateral CCJ regionvia the suboccipital far-lateral approach by dissecting the adult cadaveric specimensand efficacy of the posterior fixation for occipitocervical instability.Methods:Fifteen (30 sides)adult cadaveric specimens which perfused with coloredsilicone and 15 adult dry skulls were studied.Stepwise dissections via the far-lateralapproach to ventral-lateral CCJ region and the different exposures were comparedamong the four groups:RCA,pTCA,tTCA,and TTA respectively,and parameters aboutthe screw entry point and trajectory direction of posterior fixation were measured.Result:1.There was 83.3% occipital artery stems located at the line from the mastoidtip to external occipital protuberance,within the area of 3～5mm to posterior medianline;The mean length from verterbral artery entry dural point to the posterior medianline was 15.5±1.2mm,there was no origin of the PICA from the epidural verterbralartery;the mean length occipital condyle was 24.5±3.3mm;the mean length from theinferior edge of hypoglossal canal to the condyle was 9.1±1.1 mm;the mean height ofjugular tubercle was 9.4±1.4mm;86.7% of asterion was located behind the junction oftransverse sinus and sigmoid sinus.2.Compared with the RCA group,the exposures ofventral-lateral region in CCJ increased 10.9,12.6andl 0.l mm,the depth decreased13.5,20.5and 24.6mm in pTCA,tTCA,and TTA group respectively,there wassignificantly statistics difference among the groups(P＜0.05)3.The screw entry pointwas about lcm above the superior nuchal line and 2mm lateral to C₁ pedicle,themedial inclination angle of the trajectory wasl3.5±2.4°,superior inclination angle was5.2±0.4°,the screw length was 25.5±3.5mm.Conclusion:Suboccipital far-lateral approach could exposure ventral-lateral CCJregion,and expand the exposures by resecting condyle or jugular tubercle,it alsocould make occipitoatlant fusion by posterior atlas pedicle screw fixation.2.Study of microsurgical anatomy of the transoral approach to the craniocervicaljunction(CCJ)region and anterior fixation method Objective:To investigate the microanatomical structure in ventral-lateral CCJ regionvia the transoral approach by dissecting the adult cadaveric specimens and feasibilityof the atlantoaxis fixation by anterior transarticle screw method.Method:Cadaveric specimens were the same as those of part one.Stepwisedissections via the tranoral approaches to ventral-lateral CCJ region and the differentexposures were compared among the three groups:To,To+Ma,and To+Pa grouprespectively,and parameters about the screw entry point and trajectory direction ofanterior transarticle fixation were measured.Result:Soft tissue of the posterior pharyngeal wall consisted of five structures andtwo interspaces;the distance from the pharyngeal tubercle to anterior edge of foramenmagnum was 10.2±2.2mm;the distance from the anterior tubercle of atlas to upperincisors was 11.6±2.1 cm;the height of the dens was 15.9±6.9mm;the length oftransverse ligament of atlas was 21.7±1.6mm;the distance from the transverseligament center to dura was 2.1±0.3mm.2.The exposure extent of the transoralapproach range from lower clivus to C₂;Mandibulotomy could increase by 23.6°insagital planes and 11.1°in axial planes and decreased the depth by 2.0cm,theexposure entent of range from midclivus to C₃.Palatotomy could increase by 14°insagital angle and decreased 1.6cm in depth,but the axial angle had no significancelyenlargement,the exposure entent had enlarged to upper clivus.There was significantlystatistics difference among the groups(P＜0.05).3.The screw entry point was at thejunction of the lateral edge of C₂ verterbral body to 3mm above of inferior edge of C₂anterior arch,the screw length was 16～25mm,the lateral inclination angle of thetrajectory was 5～20°,posterior inclination angle was 15～24°.Conclusion:The transoral approach could provide with exposure entent from inferiorclivus to C2 and within 3～5cm to midline,was very suitable to resecting thedens;These modifications of transoral approach could expand the exposure anddecrease the depth;the anterior atlantoaxial transarticle screw fixation could providestability for CCJ region.