The Radiographic And Anatomical Study Of Axial L5/S1 Intervertebral Fusion (AxiaLIF)

ObjectiveTo analyze and clarify anatomical strata of the presacral approach and adjoining relationships among essential structures thereof;to gauge distances between the fundamental neighboring structures and establish a security scope for axial L5/S1 intervertebral fusion;to evaluate the feasibility and safety of applying axial L5/S1 intervertebral fusion(AxiaLIF) to domestic patients;to further study the applied value of this novel fusional technique in its clinical treatment of domestic patients.Methods(1)30 adult volunteers who are 23～25 years old were contributed to the investigation.There are 15 men who are 168～175 centimeters height,60～70 kilograms weight and 15 women who are 160～165 centimeters height,45～55 kilograms weight among them.MR images were scanned by the same technician.1.Placed in the pronation/supination position,The shortest distance from the anterior margin of the sacrum to the mesorectum was measured on median sagittal plane.2.Placed in the supine position,distances from the left/right internal iliac vein/internal iliac artery to the median line of the sacrum were measured on S1/2 slice.3.Placed in the supine position,distances from the arteriae sacralis media and anterior sacral venous plexus to the median line of the sacrum were measured on different slice.(2)6 fresh adult human age from 60 to 70 cadavers were contributed to the investigation.Placed in the operative position of AxiaLIF,the particular sect was dissected layer by layer.The point is to observe the adjoining relationships between the important structures as rectum,blood vessels,nerves and others,and measure the distance between important adjoining structures. Results:(1)Iconography1.There's no statistical difference of the distance from the anterior margin of the sacrum to the mesorectum between the pronation and supination position. The narrowest slice is S3/4 which is about 1.1 cm of male and 1.0cm of female.2.The nearest vessel to the median line of the sacrum is internal iliac vein which is more than 2.5cm.3.Sacrum transverse veins stick to the horizontal median line of sacums. The range of diameter is from 1mm to 5mm.4.There are much difference of the anterior sacral venous in different volunteers.(2)Anatomy1 Main anatomical structures of the lumbar axial by sequence the subcutaneous layer,fat layer,gluteus maximus muscle,loose connective tissue, coccyx.2.There's only fat and loose connective tissue between presacral and rectum without important anatomic structure.3.There's no important anatomic structure within the operational zone of AxiaLIF.4.There exists anterior sacral venous between sacrococcyx and fascia which is made by sacrum transverse vein,median sacral vein and parasacral vein.5.We find middle sacral artery and middle sacral vein to be a poor anatomic landmark for lacation of the midline at L5-S1.6.The average distance from the sacral(S1/2) midline to the left/right internal iliac vein is more than 2.5cm.7.The distance from the sacral foramen to the sacral midline is more than 2cm.Conclusions:1.The degree of safety of AxiaLIF is comparatively high with relatively small risks.In addition,it has evident advantages and a relatively preferred risk to return ratio,therefore,such operation is of great clinical applied value.2.In the process of XLIF,the possibility of injuring the vessels and nerves around the approach of XLIF is relatively low except middle sacral vein.3.MRI images of the pelvis should be obtained for risk assessment.4.If more effective orthophoric instruments is made for AxiaLIF,The risk of this operation could be decreased.5.Furthermore,there have not been any cases of clinically significant vascular,neural,or visceral injury.Further studies should address infection rates and the risk of soft tissue injury relative to current acess techniques for lumbosacral fusion.