| Pedicle nailing sight has the function of helping surgeons to finish path planning,it also has the function of accurate guiding the insertion of screw,those functions of pedicle nailing sight adapts to the trend that complex operation should be safe and key operation should be simple.Based on 3D printing manufacture,pedicle nailing sight has the outstanding advantages of agile manufacturing and flexible manufacturing,its difficulty in manufacturing of personalized positioning surface has been basically solved,the solution of the problem promotes the technological breakthrough.The screw channel planned in a scientifically and accurately and efficiently way,as well as the sights used in a reliable way of the operating conditions are the key points of the sight's design,manufacture and usage.Selecting the largest standard screw to make the pedicle screw fixation has better biomechanical performance,abiding by the principle that the pedicle cortex is not broke with the spinal cord,nerve root and its around vessel is not damaged,which are the gist of quality evaluation in the nail channel planning.Based on accurate,simple and efficient CAD technology,the efficiency of screw channel planning is elevated,so as to the response speed of surgery is improved,which is the important topic of revealing channel's advantage of cost-effectiveness ratio and rapid boosting its wide clinical application.This paper analyzed the existing pedicle nailing channel programming method and means with CAD technology,and pointed out that the effect of planning channel was neither ideal nor efficient,on account of these methods failed to effective use optimization design theory and method.On the basis of fully understanding the functions of Mimics and UG Imageware,and based on clarifying change's law on the channel cross section and plant nail point location with direction's change of the screw,the author took full use of CAD software built-in function as the means,according to the theory of least squares secondary correction as methods,getting more channel diameter as the target,put forward a technical route on channel planning.The main research contents and results in this paper are as follows:(1)Based on the 3D reconstruction function of Mimics and scientific computing function of Matlab,a method on automatically receiving the NURBS curve of the center line and its least squares linear equation in pedicle length range was proposed under the UG Imageware interface.The direction of the screw is corrected for the first time.(2)Based on the least squares straight line created by the maximum inscribed circle center in the normal section of fixed line for the first time,the second direction correctional method of screw was proposed.(3)A method about getting pedicle maximum inscribed cylinder diameter was put forward.The maximum inscribed circle was made in a similar ellipse closed area which framed by projection of the normal section of the second fixed line,and the founded circle is the normal section of pedicle maximum inscribed cylinder.The results in virtual experiment not only verify its security,in the same offset value,but also indicated a phenomenon that its diameter is greater than the ellipse's shorter axial which is obtained by the current elliptic equidistant ellipse method.This result laid a foundation for the selection of a bigger standard screw,as well as laid a foundation for the fixation of pedicle screws with better biomechanical performance.(4)According to the actual test results which rooted from the FDM-3D printing error correction results of guide hole tube in sighting device,in original design scheme the transition fit code of the tube and metal sleeve(H8 / js7,H8 / j7,H8 / k7)is unable to realize.So the code of transition fit is modified to H9/js7,H9/ j7,H9/ k7.(5)After took into account the Size error and shape error of guide hole tube in 3D printing means,the author also took the bonding force of interlayer in 3D printing sight.In order to investigate the interlayer whether failure or not in the greater than surplus quantity condition of three kinds of matching code,the author took H9 / k7 as the research object,and performed H9 / k7 with finite element analysis.The analysis results showed that the stripping between interlayer never happen in extreme conditions.It meant that H9 / js7,H9 / j7 would be more reliable.(6)The quality of pedicle nailing sight channel planning and transition fit effect has carried on the experimental study.Drilling experiments showed that precision and security of pedicle nailing sight was perfect,because it was made by the method put forward in the passage.Time consuming of channel planning in every sight is 2 hours,which indicated that the planning method possess advantage in efficiency. |
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