| BackgroundAs the body’s largest weight-bearing joints, Hip joint has complex anatomical structures and a deep position,it also adjacent to many important blood vessels and nerves, As the result,acetabulum fracture become one of the most challenging surgery for traumatic orthopedic surgeon. Acetabulum fracture is a kind of intra-articular fractures caused by high-energy injuries, and account for 3 percent of the whole body bone fracture, often combined femoral head fracture and neurovascular injury, etc. Acetabulum fracture has Complex fracture type and involving the articular surface, it is difficult to restore the matching relations of femoral head and acetabulum with conventional conservative treatment, and the treatment cycle is long, and has a higher incidence of postoperative complications, such as joint stiffness,traumatic arthritis, femoral head necrosis, etc. Therefore, surgical treatment has been gradually replace the conservative treatment, becoming the treatment standard of acetabulum fracture. Relative to the conservative treatment, surgical treatment has a shorter treatment period, earlier weight bearing, and have a lower incidence of traumatic, femoral head necrosis and hypostatic pneumonia, etc.Because of the complex construction and deep position,it is very difficult to expose visual operative and prone to injury the nerve, blood vessel and viscera, etc.,the surgery is facing many challenges in acetabulum fracture. Along with the development direction of surgery gradually towards to the minimally invasive surgery, accurate, personalized and intelligent operation, how to make the acetabulum fracture surgery get receive accurate and effective internal fixation with minimal trauma, realizing the target of accurately, optimized and minimally invasive surgery has become a goal for orthopedics doctors to explore for many years. First of all, in the respect of the surgical approach in acetabulum fracture surgery, with the Pararectus approach is used to treat acetabulum fractures by J. D. Bastian in 2011, who is the doctor of university of Bern in Switzerland. It has been gradually replace the ilioinguinal approach, becoming the first choice for anterior intrapelvic management of acetabular fractures. Compared with the traditional ilioinguinal approach, the new approach into the extraperitoneal spaces beside the rectus abdominis to expose the acetabulum, has a lower possibility injury the abdominal muscles, lateral femoral cutaneous nerve and the ilioinguinal nervemuscles. what’s more, the probability of inguinal hernia after surgery is reduced. In addition, the Pararectus approach has a shorten incision, less invasive ways to perform operations, as a result, The patient may suffer less pain and recovery time after the surgery, and they can have a earlier functional exercise time. For the acetabular posterior column fractures, K-L approach is still the best choice. On the other hand, with the development of imaging and digital medicine, make it possible to design personalized surgery for patients with acetabulum fractures, and lay a solid foundation for the accurate, optimal treatment of acetabulum fractures. Compared with the traditional way that rely on experienced doctors to design the surgery in brain, virtual surgery simulation has higher universality, higher precision, better visual effect and educational etc, it has gradually become an important direction of the development in surgery. Finally, we can design optimization surgery plan for patients with fracture of acetabulum through the digital medical. But how to make the virtual surgery turn into the actual clinical effect has plagued clinicians for a long time, and the emergence of 3D printing technology and mature application provides an opportunity for it. By using the CT data of patients,we can get the 3D virtual model and make the real model through the technology of 3D printing, and then using the 3D model to simulate surgery.it have good operability, high simulation and universality, has become a bridge connect the virtual surgery and the real clinical surgical treatment.There also have some scholars domestic and international have gone into the field of digital medicine and rapid prototyping technology in medical research, but the main focus were primarily on the field of maxillofacial surgery rather than the field of orthopaedic. What’s more,the rapid prototyping technology is not as mature as 3D printing technology now, only for making model rather than surgery simulation, in addition, the studies have not combined 3D printing with Digital medicine before, which greatly limit the role of both. This research combined with, To evaluate the effect of 3D printing and Digital design in the Surgical Treatment of Acetabulum fracture.ObjectiveIn view of the challenge of surgical treatment in acetabulum fracture, this research combined with 3D printing and Digital design technology to explore the feasibility of the minimally invasive, accurate and optimized surgical project through making virtual operation plan, printing 3D model of the haunch bone and pre-operative surgical simulation.Methods1. SpecimensThe pelvis and proximal femur was scanned by a Brilliance CT 64-channel scanner and the data was saved in DICOM format. The condition of scanning is which the pitch value≤1.0mm, the scanning current 200-250mAs, the scanning voltage 80-130kv and the Scan matrix 512×512. The data of the basic research is get from Department of Orthopaedics, The People’s Hospital of Guigang, Guanxi and contain 52 cases of acetabulum fracture cases from 2013 to 2014. The part of clinical data is get from the The Third Affiliated Hospital Of Southern Medical University that include 10 cases of acetabulum fractures cases from 2014 to 2015.2. Three-dimensional reconstruction of the model which is reducted2.1 Three-dimensional reconstruction of the pelvis which is Get rid of the femoral headThe CT data was imported into Mimics 14.11, using the function of "threshold" and "regional growth" to establish the model that include the fifth lumbar spine and the femoral head, andthen removing the femoral head and the fifth lumbar vertebra in virtual through the function of "3D editor" and we get the "mask" at last. Finally, we get the virtual model by calculating the information of the mask, each one has it’s unique color, we can observation model at any Angle according to our need,the virtual model is saved in MCS format.2.2 Three-dimensional reconstruction of the single fractureIn this section, we reconstruct the model of each single fracture. we separate the model along the fracture line, "3 D editor" is reused to get the single virtual mask,through the function of "display", "hidden", "selected", "separation" and "3D region growing", when the fracture line is not obvious or not completely separated, the direction of fracture line is reference to separate the fracture. By calculating the 3D information of the single "mask", we get the single model in 3D window and every model has it’s unique color display. In this window, the doctor can observe each fracture by rotating and translating the model in virtual, at last, the virtual model is saved in MCS format.2.3 virtual reduction of the fracturesIn the software of Mimics, we can realize reduction of the fractures, in the "simulation module", the fracture can be "rotated" and "translated" to reposition it’s original position. The single fracture moved reference to the fracture which position relatively constant or the otherside pelvic fracture. Finally, we apply the "merge" function to all the fractures and Save the original model, in this way,we get the virtual reduction model and output the model in STL format for 3D printing.3 Design the virtual surgery plan3.1 Select the surgical approach for the planIn this study, we choose the best surgical approach based on the principle of the minimal trauma, the most accurate and effective internal fixation. For the fracture of acetabulum anterior column, the Pararectus approach is the first choice. For the fracture of acetabular posterior column and posterior wall, K-L approach is still the best choice. If the fractures include the two columns, we must use both of them.3.2 Simulating internal fixation operation in virtualIn this section, we will simulate the operation in virtual. At first,the position of the plate should be confirmed through the function of "create curve" in Mimics, the length of the curve is same to the real plate. Second, we simulate the screw through the function of "create cylinder", and the diameter is same to the real screw, in this step,we need to adjust the position and length of the "screw" according to the actual surgery and the length should be measured and recorded. In the basic experiment research, we also need to cut the model which the plate locating through "three-dimensional cutting" function of the Mimics. And the area size should increase 1-2 mm in length and 1 mm in width. The partial restoration model, single fracture piece of export in STL format. Finally, the model of signal fracture and reduction acetabulum wouble be exported in STL format.4. Simulating the operation through 3D model4.1 Making the aluminum plateAt first, the anatomic parameters of the pelvic anatomy plate should be measured through the vernier caliper, such as the width, thickness, hole diameter and the hole spacing, the data accurate to two decimal places, the source of the pelvic anatomy plate is the limited liability company of suzhou xin rong bolt medical instrument. Then the measured data was imported in SolidWorks2012 to set up the 3D virtual model of the plate. Through the function of stretch bending, cutting and curve etc. we get the STL format of the three dimensional model. Finally,the STL model is accepted by mold factory to product the plate, then during the surface oxidation treatment for increasing the surface smoothness. This plate was used in the research of fundamental experiment and the real plate in clinical trials.4.2 Printing the 3D model with high degree of simulationThe model of single fractures and reduction in STL format were imported into the software of 3D printer Makerbot (Makerbot company, USA) and adjust the position to optimal. Choosing the print material for "PLA", print accuracy for 0.2 mm and then start to print. The basic experiment need the single fracture model and the partial restoration model, and the clinical trial need the reduction model.4.3 Simulating the operation with 3D model4.3.1 The simulation of basic experimentThe plate should be bended based on the partial restoration model and the virtual surgical plan, andthen the model of the single fracture would be used to simulate the process of reduction, and the pre-bended plate can guide fracture reduction while it is difficult to get reduction rely on ourselves. After that, putting the pre-bended plate on the reduction model to get the position which in the virtual plan and compared with eachother. When the position of the plate is ensured, the next work we should do is to simulate implanting the screw with the needle of 2.5 mm diameter refer to the plan. Each screw would be through over the both sides of the model to measure the length and the direction deviation.4.3.2 The simulation of clinical triesAt first, the plate which is the same length with the virtual surgical plan should be chosen and pre-bended based on the anatomical characteristics of the 3D model. Second, the screw were planted according to the length and direction in virtual plan, when the simulation is completed, the condition of the reduction would be observation.4.4 Comparing the digitized design and simulationIn the basic experiment, comparing the simulative position of the plate, the length and direction of the screw with virtual,and the clinical part compare the virtual with the real surgery, finally, related statistical analysis would be completed about the data.Results1. Based on the high quality data of CT, the closely simulate three-dimensional models were reconstructed with Mimics 14.11 software2. The study successfully accomplished the task of making personalized surgical plan for acetabular fractures through simulating the three-dimensional reconstruction, the separation of the fractures, the virtual reduction and the internal fixation.3. The research successfully get the 3D model with high precision rely on 3D printing technology,and complete the surgical simulation.4. In the basic study,61 plates and 424 screws were planted. The position of plates and the direction of screws were in high accordance with the digital design. The length of screws are compared with Paired-samples t Test and P=0.325 and it means that three is no significant difference between them.5.10 patients underwent the surgery successfully in accordance with the virtual design. CT data of postoperation showed highly consistency with the virtual design in location and number of plate and screw. In this study,5 plates and 102 screws were planted. The position of plates and the direction of screws were in high accordance with the digital design. The length of screws are compared with Paired-samples t Test and P=0.315 and it means that three is no significant difference between them.Conclusion1. The combination of the digital design and 3D printing technique can design the optimization operation plane for acetabular fractures.2.3D printing combined virtual surgical design could promote the accuracy and safety of surgical treatment of acetabular fractures, with a good curative effect and application value. |
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