| BackgroundWith the aging of society, osteoarthritis (osteoarthritis, OA) has become of all mankind the most common bone and joint diseases. At present, the treatment of osteoarthritis is still a major problem in the medical profession, early often take a conservative treatment, but often can not achieve the desired effect, and its outcome is more than the need for artificial joint replacement surgery, which can solve the patient’s pain, to improve living quality.Artificial total knee arthroplasty, successful or not and the influencing factors on the clinical efficacy has been an issue of concern, to achieve good clinical long-term efficacy for the indication of choice, the selection of the prosthesis, surgical techniques accurate perioperative management is very important, especially in largely on the surgical techniques, it is necessary to accurately osteotomy in three-dimensional space, prosthesis stereo placement, to achieve total knee arthroplasty biomechanics and then copy. Literature reported in addition to the general complications of infection, fat embolism, up to50%of early revision surgery and improper line of force, the positioning of the prosthesis improper and joint instability. Therefore, in order to obtain better long-term follow-up effect of anatomical reconstruction of lower limb biomechanical axis and the rotation axis of the prosthesis is to continue to explore and pursue the ultimate goal.Traditional total knee replacement surgery by the X-ray examination in the preoperative and intraoperative mechanical guide intramedullary extramedullary positioning osteotomy, the surgeon, with the naked eye, feel and experience to locate anatomic landmarks, lower limb alignment and the rotation axis of the prosthesis, and then manually crossed osteotomy and prosthesis placement and soft tissue balance. This completed by the naked eye observation of the limb and the prosthesis alignment on the line a lot of subjectivity a direct impact on the reliability and accuracy of the operation of the positioning mode, and even lead to the failure of the surgery. Traditional intramedullary positioning of potential infection and the risk of fat embolism.With the rapid development of computer science and technology, making the human society into the digital age, people have to combine the discipline or professional practice, and full use of the digital input features of computer technology, exploration, development and application of a large number of functional and practical performance of the software system used in the actual work, greatly improved the quality and efficiency. The medical field is no exception, in order to break the limitations of traditional TKA procedure, computer-aided orthopedic technology (CAOS) is the development of digital medical product, it is medical imaging technology, computer technology and the development of the space tracer technique combined The technology, also known as computer surgical navigation, surgical precision, standardization and control advantages. Computer-assisted knee arthroplasty system to its unique accuracy, confusion has long-standing problem of the surgeon, to achieve the desired effect of surgery.Since January1997, by Ken of Krakow Opti-the trak infrared navigation equipment to complete the first cases of total knee arthroplasty, and navigation technology in Europe and the United States has been more widely carried out. Key steps for the key is to reduce the error of the navigation system, navigation system, improve the accuracy of prosthesis preoperative alignment (registration), which is the basis of the different types of computer-aided artificial knee replacement surgery system, also surgery, it is the positioning of the surface marks or anatomic landmarks, patient individual bone and joint information and computer systems geometry corresponding to the input and the molding process. Therefore, the navigation system before surgery with time there will be some error, because, one, the hip center of all the navigation system to determine the dependence of small-scale movement of the hip, Victor and Hoste reported hip center sports center under the navigation and imaging data obtained compared to an average of1.6mm of deviation (0～5mm); Second, the positioning of the bone signs still by virtue of the operation by the naked eye, feel and experience to judge; signs of bone variability of the results of navigation; indicator Bone signs move will also affect the navigation accuracy of the measurement axis;4, the navigation system can not accurately locate the axis of rotation of the prosthesis, because the choice of the correct surgical parameters remain unresolved;, navigation measurement axis in non-weight-bearing position, the patella complete dislocation and deep medial collateral ligament relaxation, there are some differences with the normal axis; six, the instability of the navigation system itself.Reported in the literature navigation can be improved prosthesis alignment, line accuracy, but the navigation system is still using the traditional technique the same anatomical landmark positioning lower limb lines of force and the rotation axis of the prosthesis, thus calibrated osteotomy guide plate osteotomy is still not away from the traditional positioning reference and osteotomy instruments, to improve the accuracy of surgery based only on the basis of lines of force in the validation and calibration error. Therefore, the navigation system itself there is no good solution anatomical reconstruction of lower extremity biomechanical axis and the rotation axis of the prosthesis. In addition, the high costs and high technical requirements limit the navigation system widely used.Therefore, the existing total knee replacement are not fundamentally solve the problem of the rotation axis of the lower limb biomechanical axis and the prosthesis positioning, still using the traditional touch of a finger, and rely on personal experience and feel to determine and identify the signs of bone, thereby positioning osteotomy instruments, is still not free from subjectivity.Reverse (RE) technology is by scanning the existing physical, form a physical model in the computer, and then adjust and modify the model to achieve the design purpose. Rapid Prototyping (RP) technology is under the control of the computer, according to the CAD model of the object or CT data, made through the accurate accumulation of material objects of digital prototyping technology. Reverse Engineering Reverse Engineering and Rapid Prototyping technologies complement each other to form a new system "composite system."Reverse Engineering and Rapid Prototyping technologies are in the direction of the new engineering study has shown the important theoretical and practical significance, the combination of the two, used in the field of biomedical, has gradually become the new direction of research in the field, Its outstanding feature is the layered overlay, good at creating complex entity, and has a very high accuracy, has been widely used in maxillofacial surgery, neurosurgery, orthopedic surgery and other fields, In recent years, the technology in orthopedic gradually increased, mainly in two aspects of mock-ups and individual navigation templates. After the application of pedicle pedicle screw since Goffin1999reported navigation template technology, have been reported in the literature using the precise positioning of the navigation template in a total hip replacement acetabular center. Our team in the earliest studies reported individual navigation templates for accurate positioning of the spine pedicle and acetabular center, clinically proven navigation template accuracy, reduce the complexity of the surgery.However, the use of Reverse Engineering in a joint replacement, the country, inside and outside the literature are few reports, mainly produced in the joint three-dimensional solid model reconstruction and individualized prosthesis. Hafez and other people in2006first proposed the individual osteotomy template knee replacement, and conducted a preliminary experiment on the corpse, and achieved excellent results, the specific approach is to use reverse engineering to produce and femoral far matching individuals by the end and the proximal tibia osteotomy template. The new knee replacement method, breaking the traditional osteotomy instruments provided by the manufacturer osteotomy, the use of computer-aided registration techniques model of the prosthesis and knee osteotomy plane, and then use reverse engineering to production of the individual osteotomy template, the anatomy of the knee replacement osteotomy. But the design process is complex, thick osteotomy template design structure. The main drawback of the template design is no reasonable plan of preoperative lower limb mechanical axis and the axis of rotation, the template size is too large, long production time, the lack of adequate stability and other issues.Therefore, how the application of digital medical technology for knee replacement surgery before the detailed planning and design to explore the precise positioning of the three-dimensional CT assisted lower limb biomechanical axis, through reverse engineering technology to achieve accurate osteotomy of the individual, to obtain accurate prosthesis axis of rotation and the right line, in order to achieve alignment of knee biomechanical properties of the copy, the final use of rapid prototyping technology to produce simple and individualized navigation template to the exact operation of total knee replacement, not only is the medical profession The challenge is also to improve patients’ quality of life, protect our limited medical and health resources related to social and economic development an important issue.PurposeThe project intends to explore a virtual knee replacement operation and design of digital medical research based on the use of modern imaging, computer graphics, image processing, computational medicine, modern clinical anatomy and bone science combined interdisciplinary and multidisciplinary study to explore the two-dimensional and three-dimensional space of the lower limbs related to the axis of the objective, precise positioning, could help to design a precise positioning of the osteotomy plane and the mechanical axis of the navigation template, so as to ensure the accuracy of the osteotomy of knee replacement, and finally the use of fast molding machine production entity template for actual clinical application.Method(1)、 CT raw data and lower limb three-dimensional model database to establish: a64-slice spiral CT for scanning the lower limb scan conditions:voltage120Kv current of150mA, the thickness of0.625mm,512×512matrix. Be adjusted in the CT workstation, adjust the image gray scale, contrast, image viewing details, clear bone window tomography image, save DICOM format files. DICOM format files into three-dimensional image reconstruction software Mimics10.01use the software that comes with the domain value is set to the Bone (CT), three-dimensional reconstruction model, create a standby database, data stored in the computer "STL’ format.(2)、 Application the Geomagic Dtudio10.0software "STL" format of the data entity of operation, the reconstruction steps include point cloud data processing, surface reconstruction and3D entities, analysis of lower limb biomechanical axis positioning methods, the final data to the IGS "The format is stored in a computer.(3)、 The IGS format data in the reverse engineering software ProE operations, including:(1) virtual operating knee replacement process;②The design of a match with the femoral condyle and tibial plateau positioning the distal femur and proximal tibia osteotomy surface and femoral rotation axis of individual navigation template.(4)、The use of rapid prototyping machine, light curing, sintering, bonding process to add the material layer by layer up, and ultimately into a solid model of the actual knee replacement operation.(5)、 Imaging scan before and after the measurement of displacement in the coronal, sagittal and on the axis of the bit axis and lower limb force line, the final statistical analysis of experimental data obtained experimental results.Research(1)、 The establishment of the CT raw data and lower limb three-dimensional model of the database:healthy adults, lower extremity CT continuous scan data of six cases (aged65to70-year-old, average68.5years), scan conditions:voltage120Kv current of150mA, thickness0.625mm,512×512matrix. Be adjusted in the CT workstation, adjust the image gray scale, contrast, image viewing details, clear bone window tomography image, save DICOM format files. DICOM format file into a three-dimensional image reconstruction software Mimics10.01use the software that comes with the domain value set to the Bone (CT), three-dimensional reconstruction model, the establishment of a standby database. Reconstructed data in STL format stored in a computer to application the Geomagic Dtudio10.0software entities operating in the point cloud data, the reconstruction steps include point cloud data processing, surface reconstruction and3D entities.(2)、 Adult cadaveric lower limb specimens20,10male and10female; aged50to65years of age, with an average age of60. The specimens were randomly divided into a navigation template group and the traditional method group (n=10)20knees with total knee arthroplasty. The navigation template group in the preoperative CT scan of lower extremity total length, the use of reverse engineering software for processing the CT data, computer design a distal femur and proximal tibia osteotomy plane and external rotation axis positioning navigation template match Finally, the rapid prototyping machine production template kind for the operation of the navigation template group cadavers total knee replacement surgery. The experiment was conducted by the same one with clinical experience but no actual experience in joint replacement operations orthopedic surgeon, using traditional and navigation template of total knee replacement surgery. Observe the navigation template with the femoral condyle and tibial plateau match preoperative and postoperative CT scans were compared positioning accuracy of the osteotomy.(3)、 Clinical in30cases of patients navigation templates positioning osteotomy, total length of the lower extremity of the preoperative CT scan, the use of reverse engineering software for processing the CT data, the computer design of a distal femur and proximal tibia matching to locate the osteotomy plane and external rotation axis navigation template, and finally by the production template kind of rapid prototyping machine for surgery in total knee replacement surgery operation. The experiments done by the same orthopedic surgeon in total knee replacement surgery. Observe the navigation template with the femoral condyles and the tibial platform match, preoperative and postoperative CT scans compare the accuracy of the method of positioning osteotomy, preoperative and postoperative measurement of relevant parameters.ResultThe the Geomagic Dtudio10.0software to the exact reconstruction of the lower limb three-dimensional digital model, and precise positioning of the lower limb axis, including:lower limb mechanical axis and tibial plateau tilt axis.This study were designed and produced70digital navigation template assisted total knee replacement50cases. Navigation in the preoperative template and the femoral condyle and tibial plateau bone anatomical structures fit closely with no obvious move.Bodies of experimental navigation template group were lower limb power line deviations were less than3°, while the traditional group were lower limb power line Only11cases of deviation angle within3°, the difference was statistically significant (x2=10.384, P=0.016).The clinical proof was that, measurement of the location of the components:the amount of surface measurement, navigation templates group after FFC angle average deviation angle is less than the traditional group, the difference was statistically significant (t=-17.911, P=0.000). In all patients within the navigation template group/valgus of≤3°, the traditional group,25patients with≤3°/valgus. The navigation template set of basic no significant deviation, of7°maximum deviation of the traditional group, the difference was statistically significant (t=-11.299, P=0.000). The average deviation of the navigation template group FTC angle is less than the traditional group, the difference was statistically significant (t=-22.609, P=0.000);Sagittal measurements:LFC angle, navigation template group and LTC angle average deviation angle is less than the traditional group, the differences were statistically significant. Navigation template group mean operative time was26minutes shorter than the traditional group, the difference was statistically significant (t=-25.487, P=0.000). The navigation template group intraoperative blood loss than traditional group less410-440ml difference was statistically significant (t=-38.112, P=0.000).Conclusion The precise positioning of lower limb axis and analog computer-aided under the knee replacement process, anatomical fit closely after the navigation of virtual design templates and femoral condyle and tibial bone platform, no significant move to ensure the accuracy of the technique to locate the anatomical axis. Navigation template knee replacement distal femur, proximal tibia and femur in external rotation osteotomy accuracy than traditional methods, and the simple operation, does not destroy the canal, less blood loss, avoiding the pith cavity the risk of infection. |
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