A complex revision hip arthroplasty was performed using a custom-made implant and mixed reality technology. According to the authors' knowledge, this is the first report of such procedure described in the literature.
The technology of 3D printing and visualization of anatomical structures is rapidly growing in various fields of medicine. A custom-made implant and mixed reality were used to perform complex revision hip arthroplasty in January 2019. The use of mixed reality allowed for a very good visualization of the structures and resulted in precise implant fixation. According to the authors’ knowledge, this is the first described case report of the combined use of these two innovations. The diagnosis preceding the qualification for the procedure was the loosening of the left hip’s acetabular component. Mixed reality headset and holograms prepared by engineers were used during the surgery. The operation was successful, and it was followed by early verticalization and patient rehabilitation. The team sees opportunities for technology development in joint arthroplasty, trauma, and orthopedic oncology.
The technology of three-dimensional (3D) printing and visualization of complex structures is rapidly growing in various fields of medicine. These include cardiovascular surgery, otorhinolaryngology, maxillofacial surgery, and, above all, orthopedic surgery1,2,3,4,5. Currently, this technology is used in orthopedic surgery not only in the direct implementation of 3D printed elements, but also in surgical training, preoperative planning, or intraoperative navigation6,7,8.
Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are one of the most frequently performed orthopedic surgical procedures worldwide. Due to the significant improvement in the patient's quality of life, THA had been described in a previous publication as the "surgery of the century"9. In Poland, 49.937 THA and 30.615 TKA were performed in 201910. As life expectancy increases, there is an upward trend in the projected number of hip and knee arthroplasty surgeries. Great efforts have been made to improve implant design, surgical technique, and postoperative care. These advances led to a better chance of restoring patient function and reducing the risk of complications11,12,13,14.
However, the big challenge currently faced by orthopedic surgeons worldwide is working with non-standard patients whose anatomical defects in the hip joint make it very difficult or even impossible to implement an off-the-shelf implant15. Bone loss may be due to significant trauma, progressive degenerative osteoarthritis with an acetabular protrusion, developmental hip dysplasia, primary bone cancer, or metastasis16,17,18,19,20. The problem of implant selection specifically concerns patients who are at risk of multiple revisions, sometimes also requiring unconventional treatment. In such cases, a very promising solution is an additive-made 3D printed implant created for a specific patient and bone defect, allowing for a very precise anatomical fit20.
In the field of arthroplasty, precise implant and its sustainable fixation are crucial. Progress in preoperative and intraoperative 3D visualization has resulted in excellent solutions as augmented and mixed reality21,22,23,24. Intraoperative use of bone and implant computed tomography (CT) holograms may allow better prosthesis placement than conventional radiography images. This emerging technology may increase the chances of therapy effectiveness and reduce the risk of neurovascular complications21,25.
This case report concerns a patient subjected to hip revision surgery due to aseptic loosening. To address significant bone loss caused by multiple implant failures, the custom-made 3D printed acetabular implant was used. During the procedure, we used mixed reality to visualize the implant position to avoid damaging the at-risk neurovascular structures. Application implemented to mixed reality headset allows giving voice and gesture commands, making it possible to use it in sterile conditions during the surgical procedure.
A 57-year-old woman was admitted to the department with a preliminary diagnosis: loosening of the left hip's acetabular component. The patient's disease history was extensive. Throughout her life, she underwent numerous surgical procedures of the hip joint. The first treatment was hip resurfacing due to osteoarthritis caused by hip dysplasia (1977-15 years old), the second was a total hip arthroplasty due to implant loosening (1983-21 years old), and other two revision surgeries (1998, 2000-37 and 39 years old). Moreover, the patient was suffering from spastic left-sided hemiplegia caused by childhood cerebral palsy, and she was repeatedly operated due to left clubfoot deformity. She was also burdened with osteoarthritis of the thoracolumbar spine, carpal tunnel syndrome, and well-controlled arterial hypertension. The final diagnosis preceding the qualification for the next procedure was the pain and increasing function limitation caused by loosening of the left hip's acetabular component. The patient was highly motivated, physically active, and coping with disability.
The protocol follows guidelines of the Human Research Ethics Committee of the Medical University of Warsaw. The patient gave informed consent to the procedure and acknowledged the fact that it will be recorded. The patient agreed to that prior to the procedure.
NOTE: The basic criterion for including the patient in the surgery project was the necessity to intervene because of the anatomical dysfunction, which made it impossible to use a standard implant. Mixed reality was aimed at better placement of the prosthesis, increasing the chances of successful surgery.
1. Preparation
2. Pre-surgery checkups
3. Mixed reality model
NOTE: The process is performed to achieve proper implant and pelvis visualization, which will be used intraoperatively.
4. Surgery
5. Postoperative care
Image preprocessing
Binary masks of the pelvic bone, femur, and endoprosthesis were semi-automatically segmented from CT DICOM images by experienced radiologic technologists using thresholding and region growing algorithms with available software33. The prepared label maps were also manually corrected by a radiologist. Label maps were used to enhance the visualization by adding them to the CT scan in the next step. This approach made it possible to merge the volumetric rendering, which allows to see the bone structure and surrounding tissues on the CT scans, with the segmented parts indicating important tissues. The segmentation results were concluded in the original stack, which avoided constructing only a 3D graphical model of structures but made it possible to maintain information about all Hounsfield Units (HU) values. It resulted in an interactive visualization that allowed one to display tissues, implant and conduct bone segmentations simultaneously or one at a time, depending on the surgical situation (Figure 1 and Figure 4) visualizations of the fixed implant. The processed CT data set was visualized as holograms using dedicated software.
Pre-procedural planning and hospitalization
On the basis of computer tomography data and visualizations, an operation plan was prepared. The plan included important values: hip center of rotation, acetabular inclination, anteversion, and the direction, method and zones of implant mounting. The position of the implant was determined by bone and anatomical points, while the appropriate configuration was additionally confirmed after setting the trial head of the prosthesis and clinical checking of the implant's stability during the procedure. Post-operative CT was performed in order to confirm the correct position of the implant. The position of the screws was planned on the basis of the CT by the engineer and surgeon, which allowed to avoid contact of the screws with the vascular-nerve structures and their damage (Figure 5). The acetabular defect was classified as 3B Paprosky classification34. Type 3B is the most severe destruction of all acetabular structures, including walls and columns34. The clinical HHS score before surgery was 44 (Table 1).
Activities to prepare the patient for the procedure included internal medicine consultation and standard laboratory tests. Essential examinations were also necessary: ECG and X-ray: chest X-ray, pelvic X-ray. The control image was also taken after surgery. The patient received standard thromboprophylaxis (Clexane 40 mg, 1 x 1 s.c.) and antibiotic prophylaxis (Tarsime 3 x 1.5 g i.v.) during hospitalization. Individualized pain therapy was included. All other medications were taken according to the patient's standard recommendations.
In January 2019, an arthroplasty revision of the left hip was performed, which included the replacement of a loose acetabular component with the custom-made implant: Triflanged acetabular component, Polyethylene insert, constrained, Fastening screws-10 pieces, Co-Cr-Mo constrained modular head (36 mm), and a 9 mm neck.
The operation lasted for 4 h and was executed without complications. Verticalization with the help of a walker took place on the second day after the procedure. The patient was discharged on day 14 in a good general condition (long rehabilitation time due to foot paralysis after cerebral palsy). Control visits took place following the appointed dates. Radiological control-CTs and X-rays were performed before the surgery (Figure 3, Figure 6, and Figure 7), after the surgery (Figure 2 and Figure 8) and after 2 years (Figure 9). Implant placement was performed in accordance with the assumptions of the project. The offset, range of motion, and length of the limbs were restored. The function and patient's quality of life were relatively good on the subsequent visit and improved significantly since the initial diagnosis. Before the operation, the patient moved to a wheelchair because of pain-the patient's subjective assessment on the 10-point visual analog pain-intensity scale was 8 (VAS 8). After surgery, during rehabilitation, she stopped using two orthopedic crutches. The patient currently walks with one crutch due to foot drop-peroneal nerve palsy after previous surgery in another hospital. According to the authors' knowledge, it was the first such procedure in Poland and one of the first in the world. It was a medical student research team that proposed the idea of using modern technology in the Department of Orthopedics and Traumatology of the Musculoskeletal System.
Anatomical structures that require surgical intervention must be visible for adequate implant fixation as planned. In the case of non-standard patients with significant bone defects and deformation, the appropriate visualization and adjustment of a custom-made prosthesis are of fundamental importance for the treatment process. Proper implant fixation reduces the risk of postoperative complications such as loosening or instability. The technology of mixed reality allows without risk and in a non-invasive way to accurately visualize the pelvis, bones, and soft tissues, increasing the chances of good implant placement and even possibly shortening the time of surgery in the future. The ability to manipulate the image, for example, zooming in the selected fragments of the complex anatomical structures, allows excluding the imperfections of the surgeon's eye (Figure 10 and Figure 11). In summary, a precise, fully personalized complex revision arthroplasty was performed. The authors see opportunities for the further development of mixed reality in orthopedics, not only in arthroplasty and traumatology, but also in orthopedic oncology, where it is often necessary to perform very extensive resections with a high level of precision. The appropriate visualization of difficult-to-access anatomical areas with surrounding neurovascular structures can make surgery easier for the surgeon and safer for the patient.
Figure 1: Visualization of the fixed implant. Please click here to view a larger version of this figure.
Figure 2: X-ray one day after the surgery. The letter 'L' represents the left side of the body on the X-ray. In this case, a photo of the left hip. Please click here to view a larger version of this figure.
Figure 3: X-ray before the surgery. Please click here to view a larger version of this figure.
Figure 4: Visualization of the fixed implant. Visualization is prepared in the process of preoperative planning. It shows the potential fixation of the implant. The blue color in the visualization is the border of the implant. Please click here to view a larger version of this figure.
Figure 5: 3D project for insertion of implant fixing screws. Colors are used by engineers for better and more accurate visualization. This makes it easy to distinguish bolts having different parameters-length, cross-section. The mounting sequence can also be taken into account. The colors are illustrative and are used in the pre-operative planning process. In the process of planning the implant mounting, it is important to exclude intraoperative damage to blood vessels and nerves. Please click here to view a larger version of this figure.
Figure 6: CT-3D reconstruction before the surgery shows the hip joints and part of the femur. Visible degeneration and destruction of bone structures, pelvic asymmetry. Please click here to view a larger version of this figure.
Figure 7: CT-3D reconstruction before the surgery. Please click here to view a larger version of this figure.
Figure 8: X-ray 6 weeks after the surgery. The implant was fitted correctly, it did not come loose. Visible left hip endoprosthesis with fixing elements. X-ray in combination with the clinical examination of the patient confirms the success of the operation. Please click here to view a larger version of this figure.
Figure 9: X-ray 2 years after the surgery. Please click here to view a larger version of this figure.
Figure 10: Mixed reality user's point of view – pelvis from the front. Please click here to view a larger version of this figure.
Figure 11: Mixed reality user's point of view – pelvis from the side. Please click here to view a larger version of this figure.
Figure 12: Mixed reality user's point of view – the photo taken during the surgery – the hologram shows a part of the pelvis. Please click here to view a larger version of this figure.
Figure 13: The photo taken during the surgery – main operator, Prof. Łęgosz uses mixed reality technology. Please click here to view a larger version of this figure.
HSS SCORE | |||
BEFORE SURGERY | 6 WEEKS AFTER SURGERY | 6 MONTH AFTER SURGERY | 12 MONTH AFTER SURGERY |
44 | 74,5 | 80 | 82 |
Table 1: HHS Score table – presenting the patient's results according to the Harris Hip score before the procedure, 6 weeks after the procedure, 6 months after the procedure, 12 months after the procedure.
Primary and revision hip arthroplasty may require personalization to ensure effectiveness of treatment. However, the use of custom implants requires longer preparation for surgery compared to standard procedures. Custom-made 3D printed implants are the solution that gives a chance to restore function in non-typical patients whose disease has caused significant bone destruction29. Standard prostheses are insufficient due to advanced degenerative disease developing rapidly, bone defects caused by primary bone tumors or metastases, as well as complicated injuries or multiple revision procedures16. Custom-made implants are prepared for a specific patient with complete individualization considering anatomical anomalies and current clinical condition. The process of creating an implant requires the cooperation of orthopedic surgeons with engineers and is based on CT or magnetic resonance imaging (MRI). The preparation of the virtual implant model is complicated. It is performed by engineers who precisely determine the forces acting between the bone and the implant. The preliminary virtual 3D model is consulted with the surgeon and, after its approval, the production of the custom-made implant begins. The correct implant is delivered along with PDF file instructions for the operating team. It is accompanied by a precise plastic model of the pelvic bones and implant for training purposes and intraoperative fitting.
Preoperative planning is of great importance, especially in the context of revision arthroplasty. When qualifying a patient for the procedure, it is necessary to take into account their general clinical condition, the burden of comorbidities, and the current history of the disease15. After the team leader makes the decision, the results of computer tomography are sent to the manufacturer of the implant, and then the 6-week-long procedure begins, which includes producing a 3D model and the final version of the implant.
Mixed reality is a hybrid of real and virtual reality in which physical objects coexist with digital holograms, and interaction between them is possible in real-time21. It is now widely used in various fields, including medicine35,36,37, and it is most often used to visualize medical data such as three-dimensional CT scans or MRI38,39,40. This technology makes it possible to plan treatments more precisely, quickly access patient's data in diagnostics, or better visualize the surgical field intraoperatively41. Mixed reality has also found its application in education in basic and clinical sciences at every stage of training, including students, medical residents, and consultants.
As in the case of preparation of custom-made implants, the first stage of cooperation between doctors and engineers is medical imaging data stored in the DICOM standard. More advanced techniques used in radiology and simultaneously developing technological solutions also allow for the integration and usability of dynamic imaging data, e.g., real-time ultrasound. The next stage is rendering-processing the obtained data to make three-dimensional holograms sent to a device. The user can see the visualization as a part of his surroundings and can interact with it easily. The headset placed on the head of the operator or members of the operational team are equipped with sensors (cameras, accelerometer, magnetometer, gyroscope), allowing the holographic data to be seen as a part of the surroundings (Figure 12). The operator can control the holograms with hand gestures and voice commands, which adjust the visualization to his/her specific needs. It is possible to change size, structure, position with maintained sterile conditions. The HoloLens does not adversely affect work comfort and does not limit the field of view during the procedure when the holograms are not displayed. The medical team was previously prepared for the operation through the possibility of getting acquainted with the precise and detailed 3D printing joint and prosthesis models delivered together with the implant, as well as through training with a team of engineers. The use of mixed reality glasses is very intuitive, and the efficient use of uploaded holograms is easy to learn. The mixed reality was an effective solution, both in terms of preparation for the operation and in terms of the conduct of the procedure.
According to authors' knowledge, this is the first report on the use of mixed reality technology in hip revision surgery with the use of the 3D printed acetabular implant. It was the first intraoperative use of the device in the authors' clinical center (Figure 13). Previous publications include primary hip arthroplasty with the use of mixed reality technology. It was presented by Lei Peng-fei et al. in a 59-year-old patient with intertrochanteric fracture42. Custom-made implants and mixed reality are an increasingly popular solution used in different areas of surgery. The combination of both is an innovation with promising results. Currently, these types of treatments are experimental due to high costs and the need for appropriate preparation, there is not enough quantity to create objective original studies; however, in the near future, it will be possible due to the research grants and growing interest of clinicians. In the context of the existing and commonly used solutions during surgical procedures, X-ray or CT projections displayed on a standard 2D monitor have limitations because they do not allow viewing anatomical structures from a different perspective. It is not possible to enlarge and change the position of the structure in space. In the authors' opinion, custom-made implants and mixed reality technology is promising for difficult revision arthroplasty, as well as traumatology and orthopedic oncology. According to the authors, the mixed reality is also applicable for patients qualified for standard endoprostheses, including primary endoprostheses that do not require custom-made implants. Intraoperative navigation augmented by mixed reality allows for better and more precise placement of implants. Pilot studies are currently being carried out with promising results43.
Each stage of planning the procedure and preparing the patient is very important and none of them can be underestimated. The quality of medical imaging and the appropriate cooperation with engineers, both in the design of the implant and in the preparation of the hologram, are important for the success of the surgery. The critical moment during the procedure is the removal of the old implant components and the fixing of the new, personalized one in a previously prepared place. At this stage, holograms are important for the procedure to be performed very precisely.
The authors have nothing to disclose.
Not applicable.
The study was carried out as part of a non-commercial cooperation.
CarnaLifeHolo v. 1.5.2 | MedApp S.A. | ||
Custom-Made implant type Triflanged Acetabular Component | BIOMET | REF PM0001779 | |
Head Constrained Modular Head + 9mm Neck for cone 12/14, Co-Cr-Mo, size 36mm | BIOMET | REF 14-107021 | |
Polyethylene insert Freedom Ringloc-X Costrained Linear Ringloc-X 58mm for head 36mm / 10 * | BIOMET | REF 11-263658 |