Application Study Of Digitalization And Rapid Prototyping In Prosthetic Individualized Location Of Total Hip Resurfacing Replacement

BackgroudAt present,total hip arthroplasty(THA) has become one of most common operation,its goal is to relieve the patient'pain in the hip joint and reconstruct motor function.With the development of living standard,medical treatment and health care, requirement for artificial joint is more popular.However,as for young adults with hip arthropathy,it had higher overhauling rate for THA.Total hip resurfacing arthroplasty has been considered as an alternative to total hip replacement for adult patients diagnosed with osteoarthritis of hip or congenital hip dysplasia.Relative to conventional total hip arthroplasty,the conspicuous advantage of this procedure is preservation of femoral proximal bone that is convenient for revision if failure occurs, and others include increased range of motion,low dislocation rates and so on. Whereas,femoral neck fracture is recognized as a primary postoperative complication. It attributes to faults that appear a varus position of the femoral component and notching of the superior aspect of the femoral neck.In present years,with the improvement of materialogy,total hip resurfacing arthroplasty(THRA) has a increasing clinical application.In THRA,prothetic location is the key point for post-operative joint stability.Neck-shaft angle is determined by the design of prothesis itself in conventional hip arthroplasty,but it is determined by valgus or varus placement of femoral prothesis in THRA.When the prothesis is inserted by convertional positioning device,some help can be porvided. But accurate location can not be obtained with these devices which applied in the present.So it depended on experience at a great degree.When computer aided design(CAD) and cmoputer aided engineering(CAE) technology was led into medical domain,digital medicine has become a important ingredient of modern medicine.It spurs medical technology to develop to individualization,fidelity and mini-invasion trend.Confidence and safety have be enhanced,clinical doctors can deal with complicated operation easily.Full-resolution picture of body slice can be provided by spiral CT.Three-diamentional visional model can be reconstructed by soft Mimics,Amira and so on.Imageware is one of the four major retro-engineering software in the global.It has great function about data measurement,error detecting and contour editing.Rapid Prototyping Technology integrates modern numerical control technology,CAD/CAM technology,laser technique and new outcome of material science domain into a whole.It is widespread applied in medical domain.In this topic,we utilized preoperative spiral CT data to reconstruct individualized locating tageting template by means of three-dimensional reconstruction software,retro-engineering project software and rapid prototyping. The template can guide acetabular and femoral prothetic implant in total hip resurfacing arthroplasty.This provided a effective method for solving medical individualized problem.Objective1.To explore how to design the best direction of prosthetic repalcement by applying software Amira4.1 and software Imageware12.1 according to the patient's spiral CT data.2.According to the patient's spiral CT data,by utilizing software Amira4.1 and software Imageware12.1,to explore how to determine the normal hip rotation centre of abonormal side which depended on the character of acetabula and femoral head on normal side.It is very possible to recover the normal anatomical position after the prosthetic replacement.3.Entity model was made by rapid prototyping technology according to designed digitalized model.Model was matched to the surface of acetabula and femoral head in operation.The location of prosthesis was determined.Measurement was done by X-ray photograph postoperatively.We evaluated the accuracy of location compared with conventional method.Operative design and procedure was directed by means of this method in total hip resurfacing arthropalsty.Methods1.To determine the normal acetabular rotation centre and the prosthetic location. Data was collected which was scanned by 64-slice spiral CT machine.Data was inputted into personal computer and reconstucted by software Amira4.1.Acetabular three-diamensions model on one side was extracted according to different liminal value,preserved by STL format.Analysis was done by import acetabular digitalized model into imageware12.1.2.Definition of hip rotation centre and hip resurfacing prosthetic location.The steps were same as the former.Then analysis were made in software imageware12.1. Firstly,extract the spot-cloud data of actabular and femoral head surface on normal side.The fittest globe were produced respectively.The global centre can be considered as the acetabular or femoral head centre respectively.Secondly,presume the ideal acetabular location displayed as abductted angle 45°and anteversed angle 15°.Then,individualized digitalized locating template was made by combining actabular contour model and axial location.3.Clinical application of locating template.(1) From January 2008 to June 2008 we have selected seven patients with femoral neck fracture on one side and no obvious destruction in acetabula displayed on CT,whose symptom was so obvious that required total hip arthroplasty.All of the patients who were chosed in the study were candidates,both clinically and radiographically.Otherwise,we should consider some aspects of patients such as age,bone quality and so on.These patients' ages were ranging from sixty-three to seventy-one years.These patients were considered as one group which compared with the other group whose patients received conventioinal operation.(1) From January 2008 to November 2008 we have selected six patients with pathological changes on one hip side,who displayed acetabular pain, walk difficulty,affection for work or life.The Harris score was 22-43.All patients had received resurfacing arthroplasty.During the same time interval,we collected this kind of patients who received operation by the same surgeon,these served as the control group for the study.All surgeries were performed by the senior author through an posterolateral approach.The procedure is the same as usual process.When femoral head was dislocated and exposed well,we matched the locating template to surface of femoral head as well as possible.And Kirschner wire was inserted into femoral neck according to template.We evaluated the axial location of femoral component(showed by K-wire) with anteroposterior(A-P) and lateral position Photographs in operation by C-arm machine.The location of the wire was correct.All patients received X-ray photograph during 7-10 days period post-operatively.In order to obtain relatively accurate data,efforts should be made to decrease the error derived from photograph course.There are concerns about the angle of projection,patients' position.Standard positive photograph of hip joint must be taken,which required projecting line vertical to patients' body and centred by the hip joint center.Patients should be in supine position and inward turning 10-15°approxiately for abnormal limb.In A-P radiographs the stem-shaft angle was measured between the axial line of femur and the extension line of component stem with measuring tool of software Adobe Photoshop.Results1.Digital pelvic model can be reconstructed by software Amira4.1.By means of software Imageware12.1,acetabular rotational centre can be determined on three-dimensional pelvic model.Depending on assume the ideal prosthetic angle,the axis of prosthesis can be ascertained.Combined these results,we can design the locating template for acetabular prosthesis.The coincidence was satisfied. 2.By meas of digital pelvic model and software Imageware12.1,the normal rotational centre of acetabular and femoral head on abnormal side was reconstructed by determined the rotational centre of normal acetabula and femoral head according to mirror imaging theory.On the basis of abductted angle,anteversed angle and stem-shaft angle which we designed beforehand,the axis of acetabular and femoral prosthesis can be defined.Depending on these results,the locating template for actabuar and femoral head prosthesis can be designed.This can make the abnormal hip joint recover normal anatomic position after hip replacement.3.Analysis was performed by SPSS13.0.Data were all dispayed mormal distribution.The level of significance was defined as P values＜0.05 with 95% confidence intervals.Every group data was compared with setting certified value by single sample T-test.There were all obvious differences in each groups with regard to abduction angle and anteversion angle of acetabula,femoral component stem-shaft angles(respective corresponding value t＝2.840,P＝0.019;t＝4.157,P＝0.002;t＝2.700, P＝0.043).There were all no differences in each groups with regard to above-mentioned three kinds of angles by locating with template method(respective corresponding value t＝1.700,P＝0.127;t＝2.184,P＝0.072;t＝0.768,P＝0.477).Data between template locating group and conventional one was compared by independent sample T-test.There were all obvious differences with regard to abduction angle and anteversion angle of acetabula,femoral component stem-shaft angles between the two groups(respective corresponding value t＝2.912,P＝0.011;t＝2.486,P＝0.025;t＝2.707, P＝0.022).As a result,major error existed by conventional method,and accurate result can be obtained with locating template by designed pre-operatioin.The effect was superior to the former.Conclusion1.To reconstruct three-demensional model and analyze correlative data by means of spiral CT presentation with software Amira and Imageware,the digitized ndividualized locating template can be designed.2.Using software Amira and the Imageware,according to the three-dimensional reconstruction model of digitized pelvis,digitized localization template can be constructed for abnormal hip joint which required total hip resurfacing arthroplasty.3.Clinical result indicated that the individualized locating template for prosthesis,which was made by preoperative design,reconstruction and rapid prototyping,can orient the implant hip resurfacing prosthesis accurately for various patients.The measure can simplify procedure in operation,avoid the error caused by subjective and objective factors.