A Clinical Anatomy Research On The Lateral Approach Of Mastoid Process Surgery To Expose Lateral Mass Of Atlas

ObjectiveGet the anatomical information of important vessels and nerves which were concerned with the lateral approach of mastoid process surgery, and make sure the space relation between them and the surrounding structures to provide reference for clinical surgery.MethodsPerfusing red latex to bilateral carotid for 10 adults specimen which fixed by 10% formalin, observing and measuring the anatomical structure that were concerned with the lateral approach of mastoid process surgery. Using SPSS 13.0 to analysing the statistics.Results1 The anatomical relation between atlas transverse process or mastoid process and accessory nerve,hypoglossal nerve,occipital artery,cervical sympathetic trunk,carotid sheath .1.1 The shortest distance from atlas transverse process to accessory nerve is : left(9.5±0.16)mm, right(9.4±0.19)mm; the distance from mastoid process to the leading edge of sternocleidomastoid where the accessory nerve enter into is: left (28.5±1.63)mm; right(28.7±1.35)mm.1.2 The shortest distance from atlas transverse process to hypoglossal nerve is:left(8.4±0.16)mm; right(8.4±0.14)mm.1.3 The shortest distance from atlas transverse process to occipital artery is : left (7.3±0.29) mm, right (7.3±0.29) mm.1.4 The shortest distance from atlas transverse process to cervical sy- pathetic trunk is: left (10.5±0.40) mm,right (10.4±0.27) mm.1.5 The shortest distance from atlas transverse process to vagus nerve is: left (7.0±0.22) mm,right (7.0±0.30) mm;to internal jugular vein is:left (4.0±0.14) mm ,right (4.1±0.23) mm;to external carotid artery is:left (10.1±0.25) mm,right (10.2±0.31) mm;to internal carotid artery is:left (10.4±0.36) mm,right (10.3±0.28) mm.2 occipital artery branch from external carotid artery, it is 55 % of total above the origin of facial artery(11/20),15 % of total at the parallel level of facial artery(3/20),and 30 % of total below the origin of facial artery(6/20). The occipital artery goes to posterosuperior direction along posterior belly of digastrics, and then turn to deep direction of digastrics posterior belly, go along with the front upper side of atlas transverse process to medial of mastoid process and the sulcus for occipital artery. The diameter at original point of occipital artery is: left (2.0±0.21) mm,right (1.9±0.28) mm;the middle is:left(1.9±2.0)mm,right (1.9±0.18) mm; the point where occipital artery out of deep fascia is:left(1.9±0.22)mm,right (1.9±0.18) mm. 3 vertebral artery are branched from the posterosuperior direction of subclavian artery, through the cranny between longus colli and scalenus anterior cranny to transverse foramen of the sixth cervical vertebra, and then climb to the bone tube which consist of the transverse foramen of the sixth cervical vertebra to the transverse foramen of the first cervical vertebra, through the transverse foramen of atlas, bypass the back of lateral mass of atlas, go through the sulcus for vertebral artery which located at the arcus posterior atlantis, the anterior part is jointed with rectus capitis lateralis and lateral mass of atlas, and the posterior is covered with obliquus capitis superior and rectus capitis posterior major , then through the posterior atlantooccipital membrane and endocranium go across the foramen magnum to cranial cavity . There are 4~6 stable curve on the atlantoaxial part of vertebral artery, the vessel expand at the curve what the inside diameter is(4.7±0.90)mm, as the inside diameter of straight part is ( 3.9±0.31)mm.4 The distance from atlas transverse process to the midpoint of lateral mass of atlas is: left (28.5±0.47) mm; right (28.5±0.33) mm; the width of lateral mass of atlas is:left (16.2±1.93) mm,right (15.3±1.10) mm.Conclusion1 atlas transverse process and mastoid process have the stable relation with accessory nerve,hypoglossal nerve,occipital artery,cervical sympathetic trunk and carotid sheath , they can be the anatomic landmarks to protecting those vessels and nerves.2 There are 4~6 stable curve on the atlantoaxial part of vertebral artery, the vessel expand at the curve what the inside diameter i(s4.7±0.90)mm, as the inside diameter of straight part is ( 3.9±0.31)mm.3 The results show that the distance from atlas transverse process to the midpoint of lateral mass of atlas inner margin is(27.5~29.9)mm; the width of lateral mass of atlas is (13.1~19.7)mm。in order to protecting the spinal cord, the depth no more than 2.8 cm during the excision of lateral mass of atlas to spinal cord direction after confirming the location of atlas transverse process, or no more than 1.5 cm after confirming the location of lateral mass of atlas outer margin.