Anatomy Research Of The Upper Cervical Spine Anterolateral Surgical Approach

ObjectiveDue to the complexity of the neurovascular structures around the upper cervical spine,anterolateral approaches to the upper cervical spine are challenging.Clinically,high anterior retropharyngeal approach and the standard Smith-Robinson anterior cervical approach are chosen to treat the upper cervical lesions.The anatomy of the approaches is a crucial guide to increase the safety of the approaches to this area.We present the detailed anatomy of the two approaches of the upper cervical spine and compare the differences between them.MethodsUsing ten embalmed adult cadavers fixed with 10% formalin,we performed high anterior retropharyngeal cervical dissection of the left and right side for a total of twenty approaches(twenty sides)first of all and then performed the standard Smith-Robinson anterior cervical approach.During dissection,we recorded all anatomical landmarks,important neurovascular structures,and in particular the structures that limited exposure.The vertical distance and direct distance of each structure at the carotid sheath and larynx were measured from the prominentia laryngea and their corresponding cervical level were observed.Finally,the differences between the two approaches and the data were analyzed statistically.Results1.The neurovascular structures in this study did not demonstrate side-to-side anatomic variation;the hypoglossal nerve and laryngeal nerve were the main structures that limited the exposure.2.The cervical levels of prominentia laryngea were about 50% C5.3.The cervical levels of prominentia laryngea were about 50% C5.HyN and LiA accompanied.The vertical distance,direct distance and vertical locations of HyN and LiA were not significantly different and the levels mostly corresponded to C2.ISLN and LiA accompanied.The vertical distance,direct distance and vertical locations of ISLN and SLA were not significantly different and the levels mostly corresponded to C3 at carotid and C4 at larynx sides.The vertical distance,direct distance and vertical locations of HyN and ISLN were significantly different.ESLN and TSA accompanied.The vertical distance,direct distance and vertical locations of ESLN and TSA were not significantly different and the levels mostly corresponded to C3 at carotid and C5 at larynx sides.The vertical distance,direct distance and vertical locations of ESLN and ISLN were significantly different at larynx sides.Locations of ESLN and TSA at larynx sides close to the PML and more than half below the PML.Conclusion1.In the anterolateral cervical approach,the digastric muscle were the important signs for searching HyN.2.HyN and SLN were important anatomical structures that limited anterolateral approaches for the upper cervical spine.3.In the anterolateral approach,prominentia laryngea was important to position the neurovascular structures,vertebral locations and choose a surgical incision.4.High anterior retropharyngeal approach and the standard Smith-Robinson anterior cervical approach were effective methods for the treatment of cervical lesions.High anterior retropharyngeal approach provided excellent exposure,with a perpendicular view of the C2/3 disc level,up to one-third of the occipital slope.However,HyN and SLN needed to be dissected and pulled upwards and downwards respectively.5.In the standard anterior cervical there was no need to dissect neurovascular structure deliberately.Selecting an incision which was above PML about 13-21.8mm,we could develop the space between the HyN,LiA and the ESLN,TSA for the upper cervical spine and it might be a good starting point at the lateral margin of the larynx.The probability of damaging the vascular nerves was lower,which was safer.However,the standard SmithRobinson anterior cervical approach provided the inferior to superior oblique angle of view.It was difficullty to approach atlas,because of the location of the SLN and the need for excessive retraction,which was easily to injure neurovascular.When the lesions are limited to the vertebral body of C2 or C2 / 3 disc it could be considered.