Artificial joint replacement is an effective method for the treatment of end-stage disease of the hip and knee joint. In the past 10 to 20 years, artificial joint replacement has developed rapidly in China. More than 200,000 patients undergo primary hip and knee replacement every year, and grow at a rate of 20%, so that patients can eliminate pain, restore walking and exercise capacity, and improve their lives. quality. However, artificial joint prosthesis has a certain service life, and the initial joint replacement technique and prosthesis design are still not perfect. A certain proportion of patients need to undergo revision surgery for various reasons after 10 to 20 years.
There are more than 3 million patients with primary hip and knee arthroplasty in China. In recent years, patients undergoing artificial joint revision for various reasons have gradually increased, and will be predictably increased in a large amount within 5 to 10 years. The replacement of joint replacement brings a lot of economic burden to the society. Treatment often requires a variety of procedures, long hospital stays, long-term antibiotic treatment and rehabilitation exercises. But with the advent of 3D printing technology, it has brought a new path to hip and knee revision. The key issues in hip and knee revision and the application progress of 3D printing technology are summarized as follows.
Main cause of hip and knee revision
The causes of hip and knee revision can be divided into three categories: intra-articular biomechanical causes, intra-articular biological causes, and extra-articular causes. Mainly include: infection after joint replacement, aseptic loosening of the prosthesis, periprosthetic fracture, joint instability and joint mobility limitation. However, the main causes of early and advanced revision surgery are the main causes of early revision surgery, infection after joint replacement, periprosthetic fracture, and joint instability. The main cause of late revision surgery is aseptic loosening. Wear of the prosthesis.
Key issues in hip and knee revision
Bone Defects The goal of primary replacement and revision of the hip and knee joints is to ensure joint stability and slow joint pain. However, revisions are more complicated than initial replacements, the most common of which is the need to deal with severe bone defects and ligamentous destructive damage. Removal of the cemented prosthesis during revision surgery can result in severe loss of bone mass, but prosthesis infection may result in more bone loss during revision. Once the infected prosthesis is removed, all necrotic tissue and infected bone tissue are completely removed, often further aggravating the bone defect. Regarding the classification of bone defects, the knee joint is now commonly used by the Anderson Orthopaedic Institute's classification system (AORI) score for classification. The hip joint is usually Paprosky type, and different treatments are adopted according to different types. .
Bone graft is the main treatment for bone defect in hip and knee revision. The choice of graft includes autologous bone graft, allogeneic bone graft and metal graft. Autograft bone is mainly used for mild bone defects, and is derived from bone tissue in other parts of the body, which may be cancellous bone or cortical bone, and cancellous bone tissue including cortical bone. From a biological point of view, fresh autologous bone has the best adaptability, no rejection of the host, and can provide growth factors for bone tissue growth without the risk of transplantation. However, it has been reported that autologous bone graft can lead to pain in the patient's bone, there is a certain risk of donor complications, and the number is limited.
At present, allogeneic bone has been widely used in clinical practice. Its main advantage is that it has a variety of shapes and models, does not need to cut off its own tissue, avoids pathological changes in the material, and has osteoinductive activity, but lacks living cells, and thus has less osteogenic activity than autologous bone. In addition, allogeneic bone grafts are at risk of contracting the disease, and immune transplant responses may also occur. Structural bone grafts can be applied to larger bone defects. The main advantage of structured bone grafts is that they are relatively economical and can restore bone mass and ligament attachment points. However, it has been reported in the literature that there is a high complication rate (20%) and failure rate (22.8%) after structural graft, and the 5-year survival rate is 67% to 92%. Qi Fuxing and others believe that structural allogeneic bone transplantation should be minimized during revision. The most difficult problem in hip revision surgery is continuous interrupted bone defect. This type of concomitant rate is high, even if the plate is used to fix the anterior column of the acetabulum. And bone grafting in the bone defect, but in the case of poor healing, all the fixation is turned into nothing, and finally led to failure of renovation.
Compared with structural grafts, modular metal implant materials, especially base metals, have good biomechanical properties, close to cancellous bone, and require no removal of large amounts of bone tissue during revision, and postoperative bone reconstruction takes less time. But the cost is relatively expensive. In recent years, Brown et al reported that in 79 patients who used porous base metal in knee revision, 10 (12%) patients required secondary revision surgery and 37 (45%) patients had at least one complication.
Lachiewicz et al. found through retrospective study that 27 patients were treated with porous bismuth metal during knee revision surgery due to infection, prosthesis loosening, and bone wear. After 7 years of follow-up, 1 patient was re-renovated and only 1 patient had bone resection. The base metal is well combined.
Therefore, in the treatment of reconstructing bone defects, there is no consensus. Base metal is currently a more feasible solution than other methods. However, there are still factors such as mismatch between shape and defect, affecting the fixation of the prosthesis, poor initial stability, interface between the accessories, and high failure rate of loosening, which limits the application of metal grafts.
Preoperative planning The revision surgery is more complicated than the initial replacement of the hip and knee joint. The biggest difficulty in the current preoperative revision surgery program is how to clarify the specific model of the revision prosthesis. Defining the type of prosthesis will help to select the right tool, so that surgery time and bone loss are lost, and soft tissue damage is minimized. Shortening the time of revision surgery can help reduce the complication rate (deep vein thrombosis, hemorrhage, myocardial infarction, etc.) and improve the patient's ability to withstand surgery. It is usually only necessary to remove the original graft after surgery to clearly rebuild the prosthesis model. When the model is uncertain, an experienced and skilled surgeon must be involved in the operation. Having good preoperative planning can help reduce the likelihood of complications after revision surgery.
At present, the preoperative planning of hip and knee revision depends largely on imaging methods. The X-ray is simple and economical, and it can visually display the position of the bone structure and the prosthesis, but its accuracy for assessing bone defects and prosthetic models is not high. Spiral CT assessment of bone defects is more sensitive to X-rays, but does not show good changes in soft tissue, and can not accurately damage the soft tissue. MRI plays an important role in soft tissue assessment. Soft tissue is imaged by different sequences, but MRI has a large metal artifact and it is difficult to clearly display the patient's prosthesis after replacement. Traditional preoperative planning, clinicians must rely on two-dimensional, three-dimensional images of imaging, and then construct a three-dimensional anatomical image in the brain to evaluate bone defects. However, bones and soft tissues are a whole, and it is difficult to obtain accurate information on anatomical structure, mechanical stress, and defect range from the imagination of the mind alone. Especially for young clinicians, it is difficult to accurately determine the revision prosthesis by the current method. model.
The Need for Personalized Prostheses In the application of hip and knee joint replacement, prostheses are constantly pursuing individualization and precision. From 1891, German doctor Cluck used ivory femoral head and acetabulum to create artificial joint replacement. By 1962, in order to reduce the friction between the prosthesis, John Charnley invented PTFE as the acetabulum and metal material for the femoral stem. The prosthesis has achieved great success. In the 1970s, due to the aging of the cement interface, which caused the loosening of the prosthesis, uncemented wood began to rise, but there was also a problem with the prosthesis. Therefore, in order to adapt to the human body's load transmission and biomechanical environment, personalized artificial prosthesis began to be promoted.
Aldinger et al. began to apply CT data to customize hip prostheses, which was found to improve prognosis and reduce concurrency to a considerable extent. Bone resorption and aseptic loosening are the main factors affecting the life of the prosthesis. However, personalized prosthesis can effectively reduce and prevent bone defects and aseptic loosening. Especially in the hip and knee revision, effectively reducing the bone defect and looseness around the prosthesis will greatly reduce the possibility of secondary revision of the hip and knee joint. During the hip and knee revision process, the loss of joint bone mass and the irregularity of the joint after the fracture around the prosthesis will inevitably lead to the uncertainty of the type of the intraoperative prosthesis. The common type of prosthesis is no longer suitable. The situation of each patient. Therefore, due to the difference in patient model and bone defect caused by irregular shape in the revision surgery, this will bring great difficulty to the operation. It is not possible to accurately replace the patient with an individualized prosthesis, further correct the lower limb force line, and re-prefer the patient. Lower limb function recovery.
Surrounding fractures of the prosthesis With the popularization of artificial hip and knee joint technology, it has become the standard surgical treatment strategy for hip and knee joint diseases. Most of the patients can achieve significant improvement in joint function after initial replacement. However, due to changes in lower limb stress and osteoporosis, cases of periprosthetic fractures are becoming more common. Clinically, some complicated periprosthetic fractures are often encountered. Periprosthetic fractures occur after joint replacement, often difficult to reset, the requirements for fracture reduction are higher, the surgery depends on the surgeon's experience and surgical skills to complete, it takes a long time, postoperative complications, internal fixation Implantation needs to be done by the doctor's anatomy and surgical experience. There is a difference between each individual, and sometimes the screw enters the joint cavity, which not only increases the operation time, but also increases the exposure of the patient during the operation. Therefore, it is important for clinicians to replicate the skeletal model of the injury site and the design of the personalized internal fixation material.
Application of 3D printing technology in hip and knee revision surgery
In the past 30 years, orthopedic medical technology has made rapid progress: from open surgery to minimally invasive surgery, from the development of artificial prosthesis to the high-tech simulator being developed. A recent and innovative event is the application of 3D printing technology. It revolutionized tissue engineering, prosthesis design and manufacturing, and became part of orthopedic surgery. Contrary to traditional materials and materials, 3D printing technology is a new technology that uses layers to build materials on a 3D digital model. It not only copies the bone model to the surgeon before surgery, but also customizes the patient. Personalized prostheses for repairing bone defects have been used in artificial hip and knee replacement and revision.
Bone Defects It has been previously described that bone defects are the greatest difficulty for orthopedic surgeons in the revision of hip and knee joints. Bone grafting is currently the most widely used treatment method to ensure the stability of the prosthesis after reconstruction. The most used bone graft materials are autologous bone grafts, allogeneic bone grafts, and metal grafts.
As a new technology, 3D printing technology has been widely recognized and can be used to produce tissue engineering materials with biological properties that can control the pore size and porosity distribution, and provide a support for tissue regeneration. Recently, it has been reported that 3D printing technology is used to prepare macroporous gel methacrylamide with good bioactivity, and 3D printing technology combined with porous biomimetic technology is used to make personalized mandibular prosthesis, so that the implant not only has excellent three-dimensionality. The spatial structure, the internal microporous structure also has excellent biocompatibility, which is conducive to the adhesion and proliferation of cells, so that the living bone and the prosthesis are firmly combined to promote bone tissue repair.
At present, β-TCP has become the main production material of 3D printing, which has good biological properties, not only can promote cell proliferation and grow into pores, but also can produce prostheses with different porosity. In addition, beta-calcium phosphate can change the properties of the material by adding SrO and MgO, so that beta-calcium phosphate can be used to print prostheses with different properties as needed. In addition, with the development of technology, 3D printing materials not only promote bone healing, but also can mix drugs, such as vancomycin, in the printing powder. The low temperature printing can ensure the action of the drug, and the printed prosthesis has a good antibacterial effect.
Navigation module and preoperative planning With the increasing use of 3D printing technology in orthopedics, its application in hip and knee revision has a good prospect. Conventional surgery uses the intramedullary and external positioning guides for positioning and osteotomy. During the operation, the femur and the iliac crest are required to be positioned, and there is inevitably a certain error. Customized navigation osteotomy plate, easy to install during surgery, no need to install a positioner, can significantly reduce intraoperative blood loss and reduce the formation of circulatory thrombosis, can reduce the occurrence of complications such as pulmonary embolism. The curative effect of hip and knee revision surgery is largely determined by preoperative preparation and surgical operation. The patient's hip and knee data are obtained by routine imaging examination, and the data is converted into a three-dimensional model with the aid of computer software, through 3D printing. The osteotomy guide plate may be an effective method for reducing the operation time and bleeding volume of hip and knee joint replacement or revision, and improving the survival rate of the prosthesis and the function of the knee joint.
Pan Wei and other preoperative CT and MRI scans were used to establish a 3D anatomical model of the knee joint and simulate the operation and design guide. The intraoperative guided osteotomy was used to treat 16 cases of proximal humeral malignant tumor. The patients were followed up for 31 months without prosthesis loosening. Complications such as infections. Liu Feng et al. conducted a controlled experiment, 15 cases in the experimental group, using CT scan data, computer 3D modeling, using 3D printing rapid prototyping technology to print solid osteotomy, intraoperative guided knee replacement, 14 cases in the control group using traditional Surgical methods, 3 months after surgery, found that the operation time, intraoperative bleeding, and postoperative drainage were significantly lower in the experimental group than in the control group. The knee function score (HSS) of the New York Special Surgery Hospital was significantly higher than that of the control group. Wu Dongying and other subjects passed the control experiment. The experimental group used 3D printing technology to make the osteotomy template. The control group used the traditional osteotomy template. The knee joint activity, HSS score and lower limb force line were significantly better than the control group.
In the hip and knee revision, 3D printing technology can be tailored to the patient's individualized model, so that the choice of prosthesis model in the joint revision, the accuracy of the placement of the prosthesis and the degree of correction of the deformity are obtained. solve. The preparation of the osteotomy template for hip and knee revision will reduce the surgical trauma, shorten the operation time, reduce the intraoperative blood loss and reduce the incidence of complications, and improve the prognosis of patients.
Personalized Prosthesis The most important factor in maintaining the long-term stability of a bioprosthesis after hip or knee replacement or revision is the ingrowth between the prosthetic surface and the bone interface. There are many kinds of treatment techniques for the surface of traditional prosthesis. In the early stage, there were titanium powder spraying, titanium bead sintering, wire preparation, etc. The biggest disadvantage is that the porosity is insufficient and the aperture is not uniform, which is not conducive to bone ingrowth. The bismuth metal trabecular bone is widely used in clinical practice because its pore size, porosity and elastic modulus are close to normal cancellous bone.
However, the micro-porous coating of the bismuth metal trabeculae adopts the traditional sintering technology, and the surface treatment technology such as sintering and spraying combines the prosthesis with the surface coating, and there is a weak mechanical zone between the prosthesis and the coating, and the bonding strength is biased. Low, in the long-term use process, the surface coating may partially fall off, which may cause the prosthesis to loosen and the like needs to be renovated. 3D printing technology can use the adhesive materials such as powder metal or plastic to construct objects by layer-by-layer printing. Without the need of traditional machining and die cutting, the graphics and 3D data of parts can be directly produced by computer. , which greatly shortens the product development cycle, increases productivity and reduces production costs. At home and abroad, the use of 3D printing technology has begun to produce and apply personalized prosthesis. Cheng Wenjun et al. used titanium alloy trabecular metal cups made by 3D printing technology in total hip arthroplasty. They believed that the initial stability and early bone growth of this 3D printed prosthesis were good and the short-term results were satisfactory.
In some highly specific operations, 3D printing technology can not only simulate bone entities, but also prepare individualized surgical instruments according to surgical requirements. Lee et al used this technique to prepare individualized femoral prosthesis and femoral medullary cavity guides, which made the operation more precise and successfully performed artificial total hip arthroplasty in 2 patients with osteopetrosis. He et al. used 3D printing technology to prepare half-knee joint and artificial bone molds, and prepared individualized titanium-aluminum alloy half-knee joints and porous bioceramic artificial bones by rapid casting and powder sintering forming techniques, respectively, and assembled composite half knees. The joint prosthesis is implanted into the patient, and postoperative follow-up indicates that the composite half-knee prosthesis has good matching with surrounding tissues and bones and has sufficient mechanical strength. Liu Shenghou et al. used the pre-operative imaging data to draw the design drawings of the individualized Cage using 3D printing technology. The factory produced the Cage in accordance with the drawings, and successfully performed knee replacement in patients with loosened prosthesis. The postoperative patient's HSS score was 85 points. The function recovered well, and the joint prosthesis was not loosened in 1 year.
3D printing technology around the prosthesis is a good help for clinicians to solve the problem of prosthesis fracture. The 3D model can fully understand the fracture around the prosthesis, choose the appropriate surgery, determine the size of the prosthesis, improve the preoperative plan, and make During the operation, the navigation guide and the guiding device for guiding the internal fixation are implanted, thereby reducing the operation time and the amount of bleeding, and helping the clinician to make better decisions. Xu et al. printed a model of the pelvis 1:1 before 10 hip revisions. By experimenting with the model, the appropriate acetabular cup was selected to reduce the intraoperative time and amount of bleeding. There was no joint revision after surgery. The joint function score was significantly improved.
Won et al. used 3D printing technology to make the patient's acetabular model, developed a surgical plan for 21 patients with severe hip deformity and performed total hip arthroplasty, which significantly shortened the operation time and blood loss. Body components are accurately implanted as planned. In addition, 3D printing technology has obvious advantages over traditional fracture fixation methods for patients with complex fractures. Zeng Junjun used 3D printing technology to make a model of pelvic fracture before surgery. The Mimics software virtual steel plate is the best position. In reality, the steel plate is pre-bent and simulated in vitro. The surgeon can be handy in the operation and can reduce the operation. error. Clinically, there are also patients with periprosthetic fractures in hip and knee revision surgery. It is also necessary to fix the fracture. The application of 3D printing technology can greatly reduce the difficulty of surgery, and accurately fix it through preoperative simulation. Traditional surgery can not only reduce the operation time, but also improve the application ability of the steel plate and the bone surface, and improve the prognosis function of the patient.
The application prospect of 3D printing technology
With the continuous development of 3D printing technology, the cost is getting lower and lower, the printing speed is getting faster and faster, the operation is more and more simple, and it is necessary to print 3D model, preoperative simulation, intraoperative guidance and prosthesis transplantation before surgery. Although CT and MRI imaging techniques are irreplaceable in observing the anatomy and pathology of the affected area, establishing a 3D model can provide the best solution for surgeon treatment. In addition, using these imaging techniques, different tissues can be represented in different colors in the model. This can make the situation hidden under the prosthesis more intuitively reflected in front of the doctor, thus making the surgical procedure more smooth, thereby reducing the operation time and improving the prognosis of the patient. In the operation, 3D printing technology can print out the navigation template, which can more accurately cut out the required bone plane in hip and knee revision, and then use 3D printing technology to print out the desired personalized prosthesis, prosthetic material surface pores. The rate is more in line with the requirements, so that bone cells can better differentiate and proliferate.
Although 3D printing technology still has limitations, it will play a decisive role in the future development of hip and knee revision. Currently in the field of biomedicine, 3D printing technology has been applied to the manufacture and surgical analysis of organ models, the manufacture of personalized tissue engineering scaffold materials and prosthetic implants, and cell or tissue printing. 3D printing technology is widely used in the field of tissue engineering bone and cartilage research, and has shown good application in the field of joint surgical repair and reconstruction. The tissue engineering scaffold material prepared by 3D printing technology not only has an anatomical shape matching the defect tissue, but also has an internal porous structure that satisfies cell adhesion and proliferation.
3D printing is an exciting technology that provides a new solution to difficult and difficult problems in the past, providing a new path for hip and knee replacement revision surgery.
(Editor)
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