| BACKGROUND:Tibial plateau fracture is common complex intra-articular fracture, and the internal fixation surgery of this kind of fracture is difficult, which often accompanied by pain, joint instability and traumatic arthritis after surgery. The internal fixation surgery requires not only satisfactory biomechanical effects, but also anatomic reduction of the articular surface for the purpose of avoiding postoperative joint pain. For the treatment of complex types of fractures, surgeons should not only consider the surgical approach, surgical mode, conditions of fracture and the bone defect, but also the specifications, implant positions and screw directions of the plates and screws required for the internal fixation. This leads to a demands of high precise and efficient surgery called "personalized surgery"The appropriate implants for the internal fixation can largely determine the effect of fixation. To meet the clinical demands, the patient-specific configuration matching and screw trajectory would achieve better fixation effects. The locking compression plate (LCP) is the most popular implants in the surgery of complicated tibial plateau fractures, but various configuration and specification designs are found among different manufacturers. Therefore, mismatching between the plate configuration and specific bony structure is often encountered and the unsatisfied locking screw trajectory as well. Therefore, it happens a lot that there are no suitable intraoperative plates to be select, and the effect of the reluctantly implantation is not ideal. Currently, the internal fixation surgery of complicated tibial plateau fractures is unsatisfactory and the variable results were observed. Therefore, the appropriate preoperative plan is particularly important.However, the conventional preoperative planning was usually made by personal experience according to the two-dimensional (2D) information such as x-ray, CT and MRI. It is difficult to guide the surgery effectively and accurately, and is hard to predict the intraoperative problems. The surgical effect depends largely on the individual clinical skills, experience and proficiency detennines the success or failure of the surgery.In the recent twenty years, the "digital orthopedics" is growing rapidly. By the use of computer-assisted technology, the surgical mode of orthopedics has been changed from "open-observation-operation" to "observation-open-operation". This improvement means that the preoperative planning is conducted based on the three-dimensional reconstruction model of internal structure of individualized patient using computer-assisted technology, which would result in more accurate and optimized surgical effects. With these advantages, digital medical technology has been widely used in the surgery of trauma, spine, joint and other surgical fields. Moreover, digital technology can accurately design surgical plan, make the surgery more precise; improve the surgical quality and reliability. However, there exists a problem that how to precisely implement the surgery in accordance to the preoperative planning. In other words, the question was how to achieve the precise placement of plates and screws according to the preoperative planning in the real surgery. The rapid growing 3D printing technology has provided an excellent way to solve this problem. The virtual model of any shape can be printed into entity model using 3D printing technology. Moreover, the reduced cost, improved printing precision, enhanced printing speed and improved mechanical strength made it to be a bridge connecting the virtual design and the practical surgery.PURPOSE:1. Establishment of 3D plates library based on the CT images of commonly used internal fixation plants of tibial plateau fracture in clinic.2. Digital design of internal fixation surgical plan of tibial plateau fractures assisted by the 3D library of plates.3. To improve the accuracy of tibial plateau fracture surgery assisted by the 3D plates library and 3D-printed navigational template.METHODS:1. Establishment of 3D plates library:The clinical plates of tibial plateau were collected and underwent CT scanning. A total of 6 sets of unlocking plates and locking plates with locking screws were imaged including 2 types from 6 different manufacturers (Synthes, Zimmer, Stryker, Double, Wego, Waston). All the images stored in DICOM format were 3-dimensional (3D) reconstructed using Mimics, and then underwent smoothing to remove CT artifacts using Geomagic. Each plate was classified and stored in the 3D model library according to different types and manufacturers, which can be selected and exported for virtual surgical planning. Because the scanning artifacts resulted in unsatisfactory modeling of locking screws, 2.0 mm-diameter cylinders were used to represent locking screws, which were much easier to manipulate and allowed us to directly observe the relationship between the cylinders and bone in 3D representations.2. Digital design of internal fixation surgery of tibial plateau fractures based on 3D printing:CT images of 60 cases of clinical tibial plateau fracture were collected; all the tibial plateau fractures were 3D reconstructed and virtual reduction using Mimics. The optimized plan of internal fixation surgery was designed assisted by the 3D plates library, including the appropriate implants with the most matching shape for the individualized fracture, the most appropriate implant position and the most appropriate screw direction. The next step was to design navigational template based on the optimized plan of internal fixation. After that, the navigational template, the fracture models and the plates models were 3D printed to simulate internal fixation operation. We compared the effects of internal fixation between the virtual surgery and the simulated surgery based on 3D models, evaluated the clinical value of digital technology combined with 3D printing technology on the accurate surgery.3. The cadaver experiment verification of the optimized digital design of internal fixation surgery of tibial plateau fractures:six formalin-fixed cadaveric knee specimens were modeled to be tibial plateau fractures according to double column and three column fracture classification. All the cadaveric knee specimens were CT imaged and 3D reconstructed, and then we performed virtual reduction, optimized plan of internal fixation surgery, design of navigational template and 3D printing into entity. And then accurate internal fixation surgeries based on cadaveric specimens were performed assisted by navigational template. At last, the postoperative models of repaired tibial plateaus, plates and screws were obtained by CT scanning and reconstructed in 3D using Mimics. The analysis of fixation efficacy in terms of the deviations of screw placement between preoperative and postoperative screw trajectories were measured and compared. Furthermore, the screw lengths, entry point locations and screw directions can be precisely determined. This study is aimed to evaluate the accuracy and feasibility of internal fixation surgery assisted by 3D plates library and 3D printed navigational template.4. The clinical application of the optimized digital design of internal fixation surgery of tibial plateau fractures:Clinical cases of tibial plateau fractures were collected to perform accurate and optimized internal fixation surgery according to the method of cadaver experiment. This study is aimed to realize the accurate surgery in clinic assisted by virtual plan.RESULTS:1. The high simulation 3D library of internal fixation implants can be built using Mimics and Geomagic based on high quality CT images of implants. Locking plate combined with virtual locking screw trajectories was the standard component of 3D plates library, which not only to retain the real screw direction, but also be directly used to perform virtual surgery. This design has significant clinical value of virtual surgery. Meanwhile, the high simulation models of tibial plateau fractures can be reconstructed rapidly based on CT images using Mimics, and the virtual simulation of fracture reduction and internal fixation can also be conducted rapidly using Mimics, which plays an important role in preoperative planning, accurate and personalized surgery.2. The effects of internal fixation resulted from the simulated surgery based on 3D models were consistent with the virtual surgery ones. There was no significant difference in the deviations of screw length in the two groups (t=-1.594; v=12; P=0.137), the difference of the screw length between the two groups was-0.52±1.180mm, the correlation coefficient of the screw length was 0.994.4. In the cadaveric study, the deviations of screw length was 0.95±2.89mm, P>0.05. The displacements of entry point in the x-, y-, and z-axis were 0.25± 1.77mm, 0.31±3.14mm and 0.25±1.38mm, respectively, P>0.05. The deviations of projection angle in the coronal (x-y) and transverse (x-z) planes were 0.71±4.46° and 1.57±5.13°, respectively, P>0.05. The precision of screw placement with respected to deviations of screw length, entry point and projection angle between the ideal and actual screw trajectories did not reveal any significant difference.4. With virtual preoperative planning, we have achieved optimal and accurate fixation outcomes in the real clinical surgeries. The deviations of screw length was 1.57±5.77mm, P>0.05. The displacements of the entry points in the x-, y-, and z-axis were 1.59±5.46mm,0.74±4.98mm, and 1.76±6.50mm, respectively, P>0.05. The deviations of projection angle in the coronal (x-y) and transverse (x-z) planes were 1.59±5.17± and 1.25±7.05±, respectively, P>0.05. There was no significant difference in the deviations of screw length, entry point and projection angle between the ideal and the real screw trajectories.Conclusions:The optimal and accurate internal fixation surgery of tibial plateau fracture contained several factors, preoperative selection of high shape-matching plates, optimal implant location of plates and ideal screw trajectories. The 3D implants library is the basic of virtual surgery, which plays an important role in preoperative planning, accurate and personalized surgery. The optimal and personalized preoperative planning can be realized by the application of digital technology combine with 3D implants library. The locations of plates in the real clinical surgery can be accurately determined by the way of determining the locations of locking screws, and the placement of plates can be accurately guided by 3D printed navigational template. With virtual preoperative planning, we have achieved optimal and accurate fixation outcomes in the cadaveric study, including satisfactory placements of plates and ideal screw trajectories as the optimal preoperative planning. From the cadaveric study, we verify the feasibility of accurate surgery assisted by 3D printed navigational template. According to the experimental data and the experience, we improved the design of the 3D printed navigational template and performed accurate internal fixation surgery of tibial plateau fracture in clinical studies, which improved the effects internal fixation surgery and made an effort to achieve the personalized surgery. |
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