Knee replacement | EPFL Graph Search

Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability, most commonly offered when joint pain is not diminished by conservative sources. It may also be performed for other knee diseases, such as rheumatoid arthritis. In patients with severe deformity from advanced rheumatoid arthritis, trauma, or long-standing osteoarthritis, the surgery may be more complicated and carry higher risk. Osteoporosis does not typically cause knee pain, deformity, or inflammation, and is not a reason to perform knee replacement. Knee replacement surgery can be performed as a partial or a total knee replacement. In general, the surgery consists of replacing the diseased or damaged joint surfaces of the knee with metal and plastic components shaped to allow continued motion of the knee. The operation typically involves substantial postoperative pain and includes vigorous physical rehabilitation. The r

Numerical model of Total Knee Replacement replicating chair rising

Tshahé Auria Anongba Varela

Although the procedure of total knee replacement (TKR) has been improved for the last decades, patients may still face postoperative complications. Specially, causes of complications related to patellar resurfacing, such as osteonecrosis, patellar bone fracture, anterior knee pain and implant failure, are still unclear. Predicting strain state of the patellar bone after TKR by means of numerical modeling may help in understanding and possibly preventing such complications. First TKR model has been already developed within LBO (built in Abaqus/Standard). The model replicates loaded squat movement (Oxford rig). As the model is planned to be applied to the real TKA patients and compared with their real kinematics, squat movement could be problematic to accomplish for these patients. Thus we want also ask them to perform chair rising movement. In the project we propose to extend existing model of squat to “chair rising” movement. First, the student should study existing in vivo studies of chair rising to estimate kinematics during the movement. And then to implement this movement in Abaqus. The aim is to estimate patellar bone strain during this movement.

2014

Design and integration of an instrumented knee prosthesis

Matteo Simoncini

Total knee arthroplasty is nowadays one of the most important orthopedic surgery. It consists of a procedure in which parts of the knee are replaced by a prosthesis. The largest indication for total knee arthroplasty is osteoarthritis, a knee disease that can cause the cartilage of the femur and tibia to wear away, so that the bones rub together with use. The major risk factors for osteoarthritis are aging and obesity. Both the life expectancy and the obesity rate are increasing in the developed countries, thus the number of estimated total knee arthroplasties is growing over the years. Although over one million of prosthetic joints are implanted every year in the developed countries, none of them contains sensors to help the orthopedic surgeons in improving the precision of the replacement surgery. The goal of this study is to design an electronic system to be embedded inside a total knee prosthesis, in order to measure the force applied to it and its kinematics. Providing the orthopedic surgeons with quantitative data on the biomechanics of the prosthetic knee can help them in improving the implant precision and, as a consequence, could reduce the risk of an early revision surgery. In the frame of this thesis, we worked with the F.I.R.S.T. prosthesis by Symbios Orthopedie SA, that was instrumented with sensors and electronics to measure, process and transmit force and kinematics data to an external reader. The constraints in the design have been established by the medical doctors and the prosthesis manufacturer and the technical solutions adopted are presented. In order to simplify a future approval for human tests, we decided to keep the shape of the knee artificial joint. To achieve that, we put all the sensors and the electronics inside the middle part of the prosthesis, constituted of a polyethylene insert located between the metallic parts of the artificial joint and whose function is to reduce the rubbing. An original encapsulation was designed to guarantee the bio-compatibility of the instrumented prosthesis and to avoid a potentially dangerous contact between the electronics and the human body. This should be ensured even in case of extreme wearing of the polyethylene insert, that can occur some years after the prosthesis implant and is one of the main indications for a revision surgery. The sensors were tested by using mechanical simulators of the knee joint and validated by means of reference sensors. Different demonstrators have been designed, from the first, with only the sensors located inside the prosthesis and all the electronics fabricated in a large-scale outside of it, to the last miniaturized versions, that can be entirely embedded inside the prosthesis. Moreover, an autonomous sensor for balancing the ligaments tension during the knee replacement surgery was designed, fabricated and tested. Such a device could be an important help for the medical doctors during the surgery to improve the precision of the implant and, being not-implantable, could easily obtain an approval for human clinical trials.

EPFL2014

Studying the interactions between electro-magnetic elds and biological tissue

Laurine Kolly

Drug delivery systems (DDS) were engineered to overcome the drawbacks of more common methods such as oral pills and intravenous injections. Implantable capsules that release anesthetic drugs locally for pain management after Total Knee Arthroplasty (TKA) are currently in development within the LMIS1. The capsule will be implanted at the site of the wound during the operation and will be controlled wirelessly through resonant inductive coupling, enabling a local release of analgesics. Within this framework, this project aimed to investigate the interaction of electro-magnetic elds with the tissue that separates the transmitting coil of the controller from the implanted capsule. The main aspects that were studied consisted of the penetration of the magnetic eld and the Specic Absorption Rate (SAR). As the receiving coils on the reservoirs of capsule will each resonate at specic frequency between 300 MHz and 1.1 GHz, the aforementioned aspects were assessed at the two ends of the frequency spectrum. This was performed through the means of Finite Element Analysis, using COMSOL simulation software. To do so, models with three dierent types of media were built: air as a baseline, multi-layered tissue as an anatomically representative model, that reproduced remote power transfer to a capsule implanted at the level of the knee, and water as an approximation of the multi-layered tissue model. As a result, it appeared that, at the higher frequencies, the magnetic eld is subject to considerable attenuation, such that the power input necessary to generate sucient eld intensity at the level of the capsule in a multi-layered tissue model must be increased from a baseline of 5 W, to 10 W at 300 MHz and to 50 W at 1.1 GHz. The analysis of the SAR revealed that average peak SAR values reached are higher than the safety limit (in an uncontrolled environment) at a frequency of 1.1 GHz, and that the SAR is proportional to the power input. This implies that there is a trade-o to increasing the power input to adjust the intensity of the magnetic eld that could potentially be resolved by modifying the circuit design. Furthermore, it was concluded that approximating tissue with water may cause for the magnetic eld intensity as well as the SAR to be underestimated, due to the diering dielectric properties and to the density of water being lower than that of skin or tendon. Thus, a more anatomically accurate multi-layered tissue model should be favoured.