The Research Of Surgery Simulation For CDH Based On Rapid Prototyping

IntroductionThe Developmental Dysplasia of the Hip (DDH), which is the Congenital Dislocated Hip (CDH), refers to the hypogenesis of the coxal cavity and the femoral upper end femoral, and a series of anatomic structural abnormality and functional handicap due to the disordemess of corresponding coxal cavity and femoral head during the growth of hip. There are all kinds of clinical manifestation, with high mutilation rate, which are very difficult to cure. The disease rate of the DDH varies around the world. According to statistics, the disease rate is quite high in west Europe and north Europe, accounting for 0.9%～1.2% of the infants, but low in Africa. Based on an extensive research of treatment files, the disease rate of the DDH is 0.1%～0.4% in China.Usually, the DDH does not come on obviously. Before any OAH, there are no conspicuous clinical symptoms. However, when OAH appears, there followed the pains in hip and thigh, and limp. The course of diseases develops very fast with great suffering. The severe can lose the labour ability during the middle age. Very often, there are teenagers who did not have any obvious representation when they were young, but after the clinical OAH happens, they are already too old to meet the best cure time. The incidence rate of OAH is closely related to the degree of the dislocation of femoral head, the coxal cavity and the patient's age. It is reported that the incidence rate of OAH due to DDH reaches 43%～79%. The treatment of OAH caused by DDH is extremely difficult. The expectant treatment hardly bears fruit. Therefore, it is generally accepted that for those who have DDH along with clinical symptoms, operations are surely necessary.Because DDH is the inborn development malformation, the pathologies, for example, the coxal cavity is shallow and small, and the femoral head and mortar do not contain well, will eventually lead to subsequent OAH. Performing the orthomorphia in the prophase or at the early stage of OAH can prohibit the natural process of OAH, delay or prevent the occurrence and development of OAH, postpone or delay the hip prosthesis.There are lots of methods for orthomorphia. Although they are effective to some extent, they all share some problems and shortcomings. When clinicians are performing all the above osteotomy and hip prosthesis, they draw the conclusions from common X-ray, CT, MR/images, and recent developed CT three-dimensional reconstruction. However, all the information is two-dimensional, and has certain difference with the real deformity situation of the patient's pelvis and coxal cavity. It poses difficulties for doctors to operate accurately and realize the operation goal. At present, the orthopedics operation simulation system based on computers has been developed, but it is not mature yet and not commercialized. The system can display the dysplastic hip-join and deformed pelvis on the screen in three-dimension, but in fact it is still two-dimensional to operation performers. Two-dimensional and three-dimensional information are quite different. An accurate operation for the complicated osteotomy cannot rely on the two-dimensional information; otherwise there would be huge errors and even disputes. To realize accurate operation, it is necessary to accurately copy the patient's deformed pelvis, make operation plans and objectives before the operation, simulate the operation in advance, and collect operation parameters to guide the operation.The rapid prototyping (RP) is a new digital shaping technology based on straggling and Cumulating principles, integrating computer aided design, laser, new materials and other technologies. Since 1980s when it came out, such a modeling method originated from advanced manufacturing technology has been quickly attached great importance in the medical field. Its superiority and usefulness in human body skeleton, spatial structure rebuild and operation simulation are attracting the attention of orthopedists. It has made great progress in oral medicine, neurosurgery, orthopedics, cosmetology, tissue engineering and cardiac surgery. Nowadays, there are scholars both domestic and overseas who copied the spine, knee joint, the pelvis, os pedis, etc. with that technology to help with the operation, but there has not been any report about applying this technology in the operation of children's deformed pelvis and coxal cavity. Therefore, it is significant to copy the three dimensional dynamic model built from the images of the infant's pelvis and thigh-bone through MPI, into the tangible model through the RP technology, on which the pelvis and thigh-bone osteotomy can be simulated and the operation parameters can be collected before the operation. The research includes 3 parts:Chapter 1: The copy of the infant's pelvis and thigh-bone through the RP technology1. The value of using the MiLite View software in getting the data of cartilage2. The research on the 3D model and the RP model for the infant's pelvis and thigh-boneChapter 2: The imageology research of the children's deformed pelvis and deformed thigh-boneChapter 3: The research on the 3D model and the RP model for the children's coxal cavity and thigh-bone1. The setup of the 3D dynamic model and the RP model for the children's pelvis and thigh-bone2. The simulated operation of the children's deformed coxal cavity and thigh-bone.Chapter 1: The copy of the infant's pelvis and thigh-bone through the RP technology1. The value of using the MiLite View software in getting the data of cartilageObjective: To apply software MxLite View to manufacture the stereolithographic models of newborn infant's pelvis and femur.Methods: Firstly a dead baby' pelvis and femur was dissected, and was scanned by 64 spiral CT to get 79 images of pelvis and 131 images of femur. The MiLite View software was opened to research an image. The image was enlarged by 800 percent. The Window and Level and tool button were acted to measure the outline of pelvis and femur. When the Window and Level button were moved, the value of the image signal was increased, but the outline of pelvis and femur were the same. The images of pelvis and femur were kept by bmp form.To test the accuracy and feasibility of the method, a series of test were practiced: (1) the Window and Level values of the images of pelvis and femur were changed to increase their signals. According to stratified sampling, the femur and pelvic images were divided into three ranks: cartilage, compact bone and partial cartilage and partial compact bone. From above-mentioned three ranks, 3 images (pelvis) and 16 images were selected to test the consistency of the outline of femur and pelvis after the Window and Level values of the images of pelvis and femur were changed.Results: The outline of pelvis and femur were sample after applying software MxLite View to change the Window value and the Level value of every image, because there were no significant(Paired-Samples T Test, p＞0.05)for every images. Conclusion: The signals of pelvis and femur images can be increased successfully by the MiLite View software and the pelvis and femur outlines are the same after the signals of pelvis and femur image, so the base is established.1. The research on the 3D model and the RP model for the infant's pelvis and thigh-boneObjective: To study the manufacture of newborn infant's pelvic and femoral physical model using rapid prototyping and the accuracy of the models.Methods: A dead baby' pelvis and femur was dissected and scanned by 64 spiral CT with thickness 0.8mm, space 0.8mm, speed 3mm/sec.to get pelvic and femoral thin slice images. The newborn infant's pelvic CT images were acquired by 64 spiral CT thin slice scanning, and the slicing data of pelvis and femur were inscribed into disks by Dicom form. Software MiLite View was used to change the Window and Level values of the femoral and pelvic images. The data was transformed into bmp form; The outline of every image were extracted and trued up. According to the slice files(CLI file form), the pelvic and femoral three-dimensional modals were created , then their mirror physical models were manufactured using rapid prototyping. The accuracy of the model was examined.To test the accuracy of the models and the feasibility of the method, so experiments were put into practice:(1)firstly the samples and the models were observed and test if they were uniform. Secondly, the diameters of the samples and the models were measured to judge if they were uniform. (2) The software Photoshop 7.0.1 were used to test if the curve and angle of the samples and models were the same.Results: Firstly, the three-dimensional models of pelvis and femur were acquired successfully. The main diameters of pelvic and femoral models were similar to the ones of pelvic and femoral samples, and the curve and angle of the samples and models were the same. So we think that the models of the pelvis and femur manufactured with RP were very similar to their samples.Conclusion: The manufacture of newborn infant's pelvic and femoral mirror physical model using rapid prototyping was feasible, and the model was quite accurate.Chapter 2: The imageology research of the children's deformed pelvis and deformed thigh-boneObjective: To search the possibility of getting MRI image data of the children's deformed pelvis and deformed thigh-bone with chondromatous.Method: Get 140 pieces of MRI image for a 10 year-old boy patient whose joint in the left hip is dislocated; change the images into bmp format by the MxLite Viewsoftware; carefully read the pelvis and thigh-bone images through Photoshop 7; get only its outline for 3D imaging and get rid of others.Result: The image data of the normal thigh bone, deformed thigh bone and deformed pelvis has been correctly acquired, providing a basis for setting up the 3D model and RP model of the deformed thigh bone, pelvis and coxal cavity.Conclusion: The application of the Mxlite View and Photoshop7 software can help successfully acquire the thigh bone and pelvis outline, and the 3D model and RP model of the thigh bone, pelvis and coxal cavity are accurate. Chapter 3: The research on the 3D dynamic model and the RP model for thechildren's coxal cavity and thigh-bone and the simulated operation of these models. 1 The research on the 3D dynamic model and the RP model for the children's coxal cavity and thigh-boneObjective: To establish the 3D dynamic model for the children's deformed coxal cavity and thigh-bone, and research the pathology of the children's deformed coxal cavity and thigh-bone.Method: The pelvis and proximate femur of a 10 years old boy suffering from CDH in the left hip was scanned by 1.5T MRI to get 140 images, including 82 images of normal femur, 100 images of deformed femur, 110 images of deformed pelvis. The data of these images were transformed into bmp form by software MxLite View and were saved in the disks. The outlines of images of normal femur and deformed femur and deformed pelvis were extracted with Photoshop7.0.1. to construct their 3D dynamic models.Results: With above-mentioned methods and software, we constructed the 3D dynamic models of normal femur and deformed pelvis and deformed femur and treasure all kinds of diameters.We can observe on the 3D graph of the pelvis and the femur that the center of ossification of the femur and pelvis occur late, and that the femoral head with an irregular shape is smaller and flat, and that deformed coxal cavity is shallow and flat. The pubic symphysis growth bad. The femur neck is thin and short with a large FNA and collodiaphyseal angle. In the patient, FNA =35°, but on the normal side, FNA =5°, for the heath, the FNA is 24°. In the normal side, OA=3.85CM, OB=5.07CM, OC=4. 61CM, BA=43.9°; but in the trouble side, OA=3.58CM, OB=4. 48CM, OC=3.68CM, BA=64. 1°。Conclusion: (1) The pathology of the deformed femur and pelvis, especially the deformed coxal cavity, can be showed dynamically in the 3D models from all kinds of view, and can be used to aid surgery. (2)The 3D dynamic models can be used to simulate operation.2. The simulated operation of the children's deformed coxal cavity and thigh-bone. Objective: To search the simulated operation process by making the deformed pelvis and deformed thigh bone simulate the pelvis and thigh bone osteotomy to acquire operation parameters.Method: Simulate the trochanter rotary ostectomy and steel ostectomy; cut the coxal cavity and thigh-bone according to the above two methods, and correct the collodiaphyseal angle and anteversio angle of slope of the deformed thigh-bone; rotate the drifting coxal cavity down outward to the destination point, and use the Kirschner wire to fix the nearest and fathest points of the thigh-bone and coxal cavity; measure the distance and the angle between the os illium, ischial bone, pubis and bony suture as the parameters for coxal cavity re-location in real operation.Result: The anatomic structure and geometry structure of the pelvis and thigh bone have been successfully restored through the simulation of the trochanter rotary ostectomy and steel ostectomy, and the operation parameters have been acquired.Conclusion: The deformed pelvis and thigh bone made by the RP technology can be used effectively in the pelvis and thigh bone osteotomy. The operation parameters are accurate, which can be used to guide real operation.