Utilize The Matching Technique Of 2D-3D To Study The Relative Range Of Motion Between The Adjacent Lumbar Pedicles In Vivo

[Objective]The objective of the study is to utilize the matching technique of 2D-3D to study the relative range of motion (ROM) between the adjacent lumbar pedicle in healthy subjects with physiological weight bearing. To analysis whether the ROM of Semi-rigid-fixation(ISOBAR-system or ISOLOCK-system) is consistent with the human requirement and provide the kinematics base for the pedicle screw-based dynamic stabilization devices for the lumbar spine.[Materials and methods]Ten healthy subjects with an age ranging from 50 to 60 years (5 males and 5 females) were recruited for this study.(1)Utilize the matching technique of 2D-3D.①The lumbar segments of each subject were scanned using a 3.0 Tesla with a spine surface coil and a T2-weighted fat suppressed 3D SPGR sequence and with a thickness of 1.0 mm without gap.Make the 3D models of the lumbar vertebrae from L2-L5.②To construct the 3D coordinate system on the lumbar model's pedicle-screw entrance point.③The dual roentgenograms of the different postures of lumbar vertebrae was captured in physiological weight bearing.④The in vivo positions of the vertebrae at various weight-bearing body positions were reproduced in the Rhinoceros solid modelling software using the 3D models of the vertebra and the orthogonal fluoroscopic images.⑤The ROM between the adjacent lumbar pedicle from standing to other positions was measure from the corresponding 3D lumbar models in 6DOF. Therefore, we got the ROM between the adjacent lumbar pedicle under in-vivo weightbearing condition.(2)Semi-rigid-fixation of ISOBAR-system has a microinching joint which rotates±2°in mediolateral axis and translates±0.2 mm in sagittal direction and ISOLOCK-system's microinching joint rotates±4°and translates 0.8 mm.To analysis whether the ROM of Semi-rigid-system is consistent with the human requirement.[Results](1)The movement between the adjacent lumbar pedicle is coupling motion along the mediolateral,sagittal and cranialcauda axis, which has its characteristic.①From standing to supine, translation occurred mainly in the cranialcaudal direction(up), average 1.6～2.4 mm. The rotation occurred mainly around the mediolateral axis(anterior), average 1.9-4.2°.②During standing to flexion of the trunk, the predominant motions were translated mainly in the sagittal(anterior) and cranialcaudal(up) direction(average 1.7～2.4 mm and 1.6～2.4 mm respectively) and rotated along the mediolateral axis(flexion), average 2.8～4.0°.③During standing to extension, the motion had the similar translation in the three axes(average 1.1～2.0 mm).The rotation was along the mediolateral axis(extension) mainly(average 1.9～2.3°).④During standing to left-bending, the motion had the similar translation in the three axes(average 1.2～1.7 mm).The rotation was along the sagittal axis(left) mainly(average 2.5～2.7°).⑤From standing to right-bending, the motion had the similar translation in the three axes(average 1.2-1.7 mm). The rotation was along the sagittal axis(right) mainly(average 2.5～2.7°).⑥During standing to left-torsion, the motion had the similar translation in the three axes(average 1.0～1.5mm).The rotation was along the cranialcauda axis(left) mainly(average 2.2～2.7°).⑦From standing to right-torsion, the motion had the similar translation in the three axes(average 0.8-1.6 mm).The rotation was along the cranialcauda axis(right) mainly(average 2.2～2.3°). (2)The ISOBAR-system's ROM of rotation is smaller in flextion while similar in extension and the ISOLOCK-system similar in flextion and bigger in extension. Both of them are smaller in the cranialcaudal direction, compared with normal.[Conclusions]1.The ROM between the adjacent lumbar pedicle was dependent on body position and vertebral level.From standing to flexion, extension and supine, the adjacent lumbar pedicle rotated primarily along the mediolateral axis, when lateral bending along the sagittal axis and lateral twisting along the cranialcaudal axis. When supine and flextion, translation occurred mainly in the cranialcaudal axis, while translated in other movements, there was no difference in the three axes.2.The ISOBAR-system and ISOLOCK-system are partly consistent with the human requirement in rotation and the translation is smaller in the cranialcaudal direction, which need be improved.3.The ROM between the adjacent lumbar pedicle has provide the kinematics base for the pedicle screw-based dynamic stabilization devices for the lumbar in spine.