The Study Of The Three-dimensional Relationship Between Spinous Process In Lumbar Vertebra And The Pedicle Insertion Channel

Objective To investigate the three-dimensional relationship between the spinous process of lumbar vertebra and the pedicle insertion channel by technique of 3d reconstruction and reverse engineer and to provide anatomical basis for percutaneous lumbar spine fixation and its instrument design. Methods CT scan images of lumbar vertebra were imported into Mimics 18.0 software(Materalise) and their three-dimensional models were established. The anterior, middle, and posterior thickness and depth of spinous process were measured respectively.Then the models were imported into UG13.2 imageware for measurement.Firstly, the line L was located in the pedicle insertion channel, and the line M represented to the medial axis of the spinous process of lumbar vertebra,then the angles between two lines and the three-dimensional reference plane in 70%, 90% boundary depth were measured respectively. Secondly, the line L and the anterior surface of centrum intersected at point A, the line L and the posterior surface vertebral arch intersected at point B, the line L intersected the coronal plane at point C. Thirdly, the line M intersected the anterior wall of pedicle plate and the back edge of spinous process at point D, E respectively. Finally, the distances between point A, B, C and line L, M and three-dimensional reference plane were measured respectively. Results1.With the decrease of segment, the depth of spinous process increasedfirstly and then decreased. The spinous process could be classified into 3kinds according to its trailing edge shape, like uniform type, central type,bottom type; The diameter of screw valued 5.17 ~ 9.48 mm,length valued 24.82~33.93mm; 2.(1) The distance from points to lines changed regularly, with the decrease of segment, the distance from point A to line M decreased, the distance from point B and C to line M increased, the distance from point D and E to line L increased.(2)The angels between the medial axis of the lumbar spinous process and the sagittal, coronal and horizontal planes were 2 ~ 3o, 11 ~ 18o and 71 ~ 77o respectively.(3) The angles between the pedicle insertion channel and the sagittal plane in 70%, 90%boundary depth were 7 ~ 22o and 16 ~ 33o respectively. The angles between the pedicle insertion channel and the horizontal plane in 70%, 90%boundary depth were 1.8 ~ 2.9o and1.4 ~ 2.4o. The angles between the pedicle insertion channel and the coronal plane in 70%, 90% boundary depth were 67 ~ 82o and 56 ~ 73o. Conclusion According to the three-dimensional morphometric measurements of lumbar spinous process and pedicle insertion channel, the insertion angel for personalized percutaneous pedicle screw fixation could be confirmed and provide the anatomical basis for percutaneous lumbar pedicle screw placement and its instrument design.