Development And Mechanical Performance Test Of A New Type Of Pedicle Screw Rod System

Objectives:Based on the summary and analysis of the problems and shortcomings in the long-term clinical application of the third-generation pedicle screw and rod system,a new and improved design was made for the third-generation pedicle screw and rod system,and the two systems were mechanically modified.Testing and comparison of mechanics and biomechanics to evaluate the new pedicle screw rod system.Methods:On the basis of summarizing and analyzing the clinical data of the failures in the clinical application of the third-generation pedicle screw and rod system,such as broken rods,broken screws,and loss of rotation correction,as well as consulting related literature data,1.Make new designs and improvements to the defects and deficiencies in the design of the third-generation pedicle screw rod system:(1)In order to solve the insufficiency of the "point-point”contact between the third-generation pedicle screw rod system and the pedicle screw tail chute and locking screw,the new system combines the two The fixed contact method of the author is transformed into a“surface-to-surface contact”method in the design concept:①In terms of fixing rod design,the traditional titanium round rod is improved to a square round rod.The cross section of the square round rod is obtained after rounding the cross section,so that it can be tightly fixed to the following improved new pedicle screw In the U-shaped groove and the locking screw.②In terms of pedicle screw design,the thickness of the two wings of the new pedicle screw tail is increased,and the bottom surface of the tail U-shaped groove and the two wings near the bottom half of the bottom of the nail body and tail connection morphology structure,and the square rod structure Matching,produced by the inverted mold process that matches the structure of the square and round rod;the grooves on the inner and outer sides at 1/2 of the two wings of the nail tail form the breakable part,and the breakable part is the boundary,and the U-shaped groove is formed as a whole The "wide upper and lower lower" state makes it easy for the square rod to be clipped into the nail tail at the upper 1/2 part,and fit closely with the groove at the lower 1/2 part;there is a thread structure above the lower 1/2 inner side of the wings on both sides.Let the fixing bolts be screwed in and tightened so that the fixing bolts and the square rods can be closely attached.The integral structure can effectively prevent the rotation or rolling of the square rod in the U-shaped groove of the nail tail.(2)In order to solve the problem that the diameter of the pedicle screw body-to-tail connection junction area of the third-generation pedicle screw system becomes smaller and becomes a weakened area,the new pedicle screw is easily broken.The body-tail connection to the upper 1/3 of the nail body is designed to be tapered,so that the structure is gradually reduced in diameter from the connection to the nail body.The overall length of the cone is about 1cm,and the surface of the tapered structure is designed to be cancellous For bone threads,the thread pitch is 1/2 of the normal thread pitch to increase the gripping force from the nail body to the upper 1/3 of the nail body;in appearance,the overall nail tail is in a mixed-space screw state.2.According to the industry test standards of the spine internal fixation system,the new pedicle screw rod system was tested with pull-out force,single screw lateral pressure test,four-point bending test,pedicle screw axial push test,and compression of the internal fixation system.Bending and torsion mechanical performance test,fatigue test and other mechanical mechanical tests,and compared with the general spinal internal fixation system.3.Select 14 pigs with similar body size and size of about 200 kg.After slaughter,select the T14-L5 segment of the spine,divide the pig spine specimens into two groups randomly,and use the new pedicle screw system and universal spine fixation.The system(USS)fixes its L1-L3 segments,and uses medical viscose plaster bandages to uniformly fix the T14-T1 segments and L3-L5 segments,only the test segment is exposed,so that the test load is accurately loaded on the test segment on.In addition,plaster planes are established at the upper and lower ends of the spine to facilitate smooth and accurate loading of loads and improve measurement accuracy.Measure the load-displacement of the sample under different conditions,and compare the two sets of data.Results:In terms of mechanical and biomechanical properties,the new pedicle screw system is better than the traditional third-generation pedicle screw system in terms of resistance to torsion,pull-out force,and fatigue resistance.The differences between the two are Statistical significance(P<0.05);In terms of axial compression,flexion,extension,and lateral flexion,there is no significant difference between the new pedicle screw system and the third-generation pedicle screw system(P>0.05).Conclusions:Compared with the third-generation pedicle screw system,the new pedicle screw system has similar fixation effects and biomechanical stability in terms of axial compression,flexion,extension,and lateral flexion.The new pedicle screw system is better than the third-generation pedicle screw system in terms of rotation correction,anti-torsion,pull-out resistance,and anti-fatigue.