Objective: The simulation of the suboccipital posterior median approach was conducted on adult wet cadaver head specimens,with the aim of analyzing the microanatomy and determining the relevant structures involved in the operation.This process facilitated a comprehensive understanding of the approach and its corresponding structural characteristics,providing a robust anatomical foundation and reference for clinical practice.Methods: A total of ten wet cadaver head specimens were selected for fixation and antisepsis using formalin.The blood vessels were thoroughly washed and subsequently perfused.The suboccipital posterior median approach was simulated under a microscope,and the microanatomy was examined layer by layer from the outside in,until direct access to the fourth ventricle area was achieved.Relevant structures were exposed,allowing for the examination of the general relationship between them and the accurate measurement of microanatomical features of involved structures such as blood vessels and nerves.Data were processed using the statistical software SPSS 26.0,with results presented as mean(x)± standard deviation(S)(unit: mm)and interval [min max].Results: 1.The trapezius muscle insertion is attached to the medial part of the superior line,below the external occipital tuberosity and the spinous process of the cervical and thoracic vertebrae.The width of the attachment to the medial part of the superior line is(30.74±3.71)mm,while the occipitofrontal muscle is attached to the upper 3-5 mm.2.The splenius capitis muscle originates from the outer third of the superior line and the posterior margin of the temporal bone mastoid process,extending to the spinous process of the lower cervical spine and the posterior margin of the thoracic spine.The width of the attachment is(45.74±4.03)mm,and the distance between the medial edge of the attachment and the median sagittal plane is(52.43±5.21)mm.3.The insertion point of the semispinalis capitis muscle is attached to the skull between the upper nuchal line and the lower nuchal line.The lateral side is attached to the junction of the occipital mastoid suture,and the medial side is attached to the external occipital ridge.The width of the attachment point is(42.36±5.11)mm.4.The upper attachment of the longissimus capitis muscle is connected to the posterior edge of the mastoid process,originating from the transverse processes of the middle and lower cervical vertebrae,the upper thoracic vertebrae,and the small articular processes of the middle and lower cervical vertebrae.The distance from the mastoid attachment to the mastoid tip is(7.33±0.99)mm.5.The insertion point of the obliquus capitis superior muscle is attached to the skull between the upper nuchal line and the lower nuchal line.The width of the insertion point is(18.36±2.64)mm,and the distance from the medial edge of the insertion point to the midsagittal plane is(29.17±4.48)mm.6.The origin of the inferior oblique capitis muscle is in the spinous process and lamina of the axis.The length of the inferior oblique capitis muscle is(49.30±5.34)mm.7.The rectus majus also originates at the axial spinous process,with the lateral edge of the insertion attached to the lower part of the obliques’ insertion on the head.The width of its attachment point is(35.32±5.18)mm,the length of the inner edge is(39.39±4.53)mm,and the length of the outer edge is(45.48±6.00)mm.8.The posterior minor rectus capitis arises from the posterior tubercle of the atlas,extending to the medial nuchal plane of the inferior nuchal line and terminating at the medial deep plane of the posterior major rectus capitis.The width of its attachment point is(19.99 ±3.16)mm.9.The distance from the point where the occipital artery crosses the trapezius muscle to the midline is(28.18 ± 2.30)mm.10.The distance from the vertebral artery traversing the atlas fascia to the midsagittal plane is(21.97±2.74)mm,and the diameter of the middle of the third segment of the vertebral artery is(3.66±0.54)mm.The distance between the posterior edge of the vertebral artery sulci and the midline is(19.60±1.20)mm,and the distance between the anterior edge of the vertebral artery sulci and the midline is(11.42±1.04)mm.11.The distance from the greater occipital nerve passing through the trapezius muscle to the median sagittal line is(25.01±3.60)mm.12.The distance between the herringbone seam and the external occipital protuberance is(62.40±2.73)mm,the distance between the external occipital protuberance and the posterior edge of the foramen magnum is(50.69±3.30)mm,and the distance between the midpoint of the external occipital ridge and the posterior edge of the foramen magnum is(24.38±2.67)mm.The anterior-posterior diameter of the foramen magnum is(36.73±5.53)mm,and the left-right diameter of the foramen magnum is(29.96±5.69)mm.The left side of the transverse process of the atlas measures(9.14±0.19)mm,and the right side measures(9.54±0.30)mm.A total of 20 occipital condyles were measured in 10 specimens,with an average length of 22.96 mm,an average height of 9.48 mm,and an average width of 12.68mm.13.A weak point is present on both sides of the inner side of the foramen magnum.The distance between the weak point and the posterior edge of the foramen magnum is as follows: left side(18.07±1.80)mm and right side(18.64±3.27)mm.14.The length of the fourth ventricle floor is(37.94 ± 0.78)mm,the width of the fourth ventricle floor is(17.34±0.39)mm,and the height of the fourth ventricle is(22.71±2.15)mm.15.The muscles attached to the spinous process of the axis include the inferior oblique muscle of the head,the major rectus muscle of the posterior head,and the semispinalis muscle of the neck.Conclusion: Acquiring a thorough understanding of the microanatomy of the suboccipital posterior median approach,as well as the essential nerves,blood vessels,muscles,and the fourth ventricle involved in the approach,is crucial.Detailed measurement and analysis of relevant anatomical structures,and comprehension of the relationships and anatomical features of each structure are necessary.In particular,protecting occipital muscles is of great importance.During suboccipital posterior median craniotomy,when the incision involves the spinous process of the axis,special attention should be given to preserving the superior oblique muscle,the posterior major rectus muscle,and the semispinalis cervicalis muscle attached to it.This precaution can significantly reduce the incidence of postoperative cerebrospinal fluid leakage and enhance the stability of the cervical vertebrae.The vertebral artery is a vital source of blood supply to the brain.It meanders through the atlantoaxial segment at varying angles,adapting to complex head and neck movements.The intricate shape of the vertebral artery also increases the risk of surgery in the craniocervical junction area.When C1 needs to be exposed,careful separation should be maintained,and familiarity with the vertebral artery’s variations and anatomy is essential to effectively avoid injury to the artery and its branches.Unlike experimental settings,actual surgical procedures should be performed with greater caution to prevent damage to surrounding structures through excessive force.This study offers insights into the microanatomy characteristics of the relevant structures involved in the suboccipital posterior median approach,providing a valuable reference for neurosurgeons.By increasing the success rate of surgery,this knowledge can contribute to improved prognoses for patients. |