The Research And Application Of Hexapod Parallel Mechanism In The Reduction Of Posttraumatic Long Bone Displacement

Purpose: The deformities of traumatic long bone fracture is one of the most common disease in orthopedics department,the external skeletal fixation has been applied and get a lot of successful clinical cases.However,the mainstream of the external fixation were all used X-ray as a measurement basis,with the restriction of the point light projection principle and manual measurement way,this kind of method is inaccuracy.Aimed at this shortage,this article has improved the traditional measurement way and put forward a new technology based on 3D reconstruction to correct the deformity of long bone fracture,then verified its feasibility,accuracy,effectiveness and if it can improve the accuracy of the reduction of fracture in clinical.Methods:(1)We retrospectively reviewed 21 patients(17 males and 4 females),average age of 42 years(range 14 to 76 years),who underwent a Stewart platform for the deformities of open tibial fracture from Feb 2016 to Aug 2016.We got the postoperative limb posterior-anterior and lateral view X-ray(GE XR656)and CT data of Dicom format(GE 750)of all the patients.(2)Then we used Mimics 17.0 and Coreldraw X7 to improve the traditional measurement to apply in clinical,and evaluate the effect.(3)Next,generated the 3d reconstruction model by the software of Mimics.(4)Then we registered the ring o f Stewart platform of 3d reconstruction model used the precise ring,and merged the precise ring with the 3d model of bone segment to implemented synchronous virtual restoration and recorded the key points of multiple movement.(5)With the aid of Solidworks,we extracted the relative position of distal ring and proximal ring of the Stewart platform.(6)And then used the software of Matlab to kinematics solution,computing the targeted length of every branched chain in the movement,so we obtained the accurate adjustment scheme.(7)Last,took the standard anteroposterior and lateral X-ray of the injured limb after adjustment to evaluate the residual deformity,and carried on statistical analysis.Result:(1)The deformities of fracture of all the patients corrected well.After reduction,the mean postadjustment residual deformity were 2.9±2.5mm and 1.3±1.1 ° on the anteroposterior radiograph,the mean postadjustment residual deformity were 2.8±2.0mm ? 1.2±1.1°on the lateral view,all achieved function reset standards.(2)The new method based on 3D reconstruction has the higher accuracy to reduction in theory.After data analysis,we can get that the mean preadjustment and postadjustment residual deformity and the degree of improvement were 3.3±2.7mm(52.17%),1.3±1.2°(72.92%)and 1.2±1.0mm(82.61%),0.8±1.1°(83.33%)on the anteroposterior radiograph.And the mean preadjustment and postadjustment residual deformity and the degree of improvement were 2.8±1.8mm(42.86%),1.3±1.1°(53.57%)and 0.9±1.1mm(81.63%),0.5±0.9°(82.14%)on the lateral film.And the degree of improvement of the new method are all higher than that one in traditional way.After statistical analysis we can get that the new method is better than the improved way in anteroposterior displacement,lateral displacement and lateral angle,and there was obvious statistical significance(P<0.05).But it was not statistically determine whether the same advantage in anteroposterior angle,because there was no obvious statistical significance(P=0.159).We also can get that the new algorithm based on 3D reconstruction is better than the method based on two-dimensional measurement in comprehensive analysis.Conclusion:(1)In this paper,the improved method can improve the accuracy in theory compared with the traditional way.(2)The new algorithm based on 3D reconstruction to correct the deformity of long bone fracture can reduce the identified difficulty of the fracture parameter and it has a higher accuracy compared with the existing method of two-dimensional X-ray measurement.This method can be used for the adjustment of the residual deformity after fracture reduction,at the same time it provide a certain reference for intraoperative automation restoration technology.So it has extensive clinical use and worth to promote.