Measurement Of Distal Tibial Medullary Cavity Morphology And Biomechanical Analysis And Precise Implantation Of Poller Screw In The Distal Tibial Fractures

Background and objectivesIntramedullary nail is widely used in clinical treatment because of its good biomechanical properties and the ability to protect the soft tissue around the distal tibial fracture.However,the high incidence of malposition and angulation deformity limits the application of intramedullary nails in distal tibial fractures.The poller screw can assist the intramedullary nail to maintain a central position in the medullary cavity and provide additional mechanical stability,expanding the indications of tibial intramedullary nail in the treatment of distal tibial fractures.However,the lack of basic research evidence makes the clinical consensus on the location and plane of the poller screw placement still not formed.Because of the limitation of anatomic conditions of distal tibia and the possible risk of implant failure,the application of poller screw in the treatment of distal tibial fractures is still a challenge.Therefore,this study explored the biomechanical properties of the poller screw in different planes and different implantation position through three-dimensional quantitative measurement of the tibial medullary cavity,finite element simulation calculation and biomechanical analysis,and realized the effective and precise implantation of the barrier nail through 3D printing personalized guide plate.Methods and materials1.76 three-dimensional models of adult tibia were created.Use Mimics to re-slice the medullary cavity and measure the key anatomical parameters of the established model of the distal tibial medullary cavity morphology.2.The three-dimensional finite element model of tibia was established by software,and the models of the experimental group were grouped according to the plane and position of the placement of the poller screw,and the model with only intramedullary nail implanted was taken as the control group,and the finite element simulation calculation of the implantation of the poller screw at different position was carried out by applying physiological loads.3.16 intact tibial embalmed tibial specimens were collected to simulate the implantation of intramedullary nails and poller screw.The distal tibial pollerscrew was implanted with the help of personalized auxiliary guide system(guide group,n=8)or C-arm machine(freehand group,n=8).The accuracy was evaluated by comparing the absolute value of the deviation between the actual implant position of the poller screw and the virtual surgery placement position in the nail head and tail.Result1.In the sagittal and coronal planes,the ratio of the diameter of the medullary cavity of the tibial medullary cavity stenosis to the diameter of the distal tibial medullary cavity in men and women is greater than 1.25 in the P4-P10 plane.2.Under physiological load,the axial stiffness of intramedullary nail group was 6897±427.43 N/mm;The maximum axial stiffness of the sagittal plane group was 8273 ± 498.65 N/mm(P<0.05);The maximum axial stiffness of the coronal group was 7930±571.42 N/mm(P<0.05).3.Under an axial load of 500N,the length of segment A between fractures line is 0.0624±0.0004 mm and segment C0.0568±0.0004 mm(P<0.01);Line segment B is 0.0580±0.0007 mm,and line segment D is 0.0616 ± 0.0005 mm(P<0.05).4.In the guide plate group,the screw head deviation was 2.33±0.64 mm,and the screw tail deviation was 3.11±0.93 mm(P<0.05);The screw head deviation of the bare handed group was 4.18±1.03 mm,and the screw tail deviation was 6.03 ±1.61 mm(P<0.05).The incidence of implantation failure events was 3 cases in the free hand group and 1 case in the guide plate group.Conclusion1.The intramedullary nail is difficult to contact with the wall of the medullary cavity at the P4-P10 plane of the distal tibial medullary cavity,and the decreased stability provides a reference for the clinical use of poller screw.2.The placement of the poller screw at P1 and P2 position can obtain higher axial stiffness.The placement of the poller screw will have an impact on the symmetry of fracture space movement.3.Personalized guide plate can achieve more accurate nail placement results than bare handed nail placement,providing a new method for clinical use of poller screw.