Total knee arthroplasty is a widely performed surgical technique. the early 70s, a new concept for TKA prosthesis was introduced: total condylar prosthesis. Previously encountered problems of hinged prosthesis have been solved using 850649-61-5 IC50 this semiconstrained design that recreates both the patellofemoral and femorotibial joints. The total condylar prosthesis, as represented in Figure 1, is composed of three main parts for recreating the tibiofemoral joint: a femoral component, an ultra-high molecular weight polyethylene (UHMWPE) insert and a tibial component. Additionally, on the knee cap, a patella button can be assembled, which slides on the anterior part of the femoral component. Figure 1. Total condylar RFC4 prosthesis. Although the design of such prostheses has seen some minor improvements, their functional principle is similar to that of the one created by Insall TKA has now become a common operation, with over 600,000 surgeries per year in the United States alone [3] and it is the most efficient tool for solving OA-related knee pain. The success of this surgery has led to more and ever younger patient implantations, hence a need for improving stability and longevity of the implant and reducing the number of heavy revision surgeries. Smart or instrumented prosthesis contain sensors that enable monitoring the position or mechanical state of the prosthesis through some telemetric method. Research efforts have been focused on using different technologies for force sensing such as strain gauges or Bragg gratings [4]. Instrumented implants typically rely on modifying the shape and functionality of the prosthetic parts, affecting surgical protocols and prosthesis performance thereby reducing the acceptance of the device amongst surgeons and patients. Most instrumented knee prosthesis prototypes alter the metallic tibial component of the prosthesis [5C10]. However those devices involved thickening and extending the tibial part, leading to more bone removal during surgery. Additionally, they showed low remote powering efficiency [10]. The integration of the sensors and electronics in the polymer inserts [11C15] allows for wireless communication and a better remote powering efficiency [14] without adding any component or changing the external surface or function of the insert. However, the insert is a place of high strain and potential wear 850649-61-5 IC50 where the sensing system could potentially increase risk of failure. Such prosthesis malfunction or aging should be detected by monitoring the insert mechanical behavior. Intra-operative devices based on insert instrumentation were designed for force measurement in the condyles [16]. Such tools, knee prosthesis implantation. In this study, we fabricate and test a device for measuring force in each condylar compartment of a UHMWPE knee prosthesis insert. We propose to incorporate a thin film microfabricated strain sensor in a hollowed stack of FR4 PCB layers: measuring 850649-61-5 IC50 the deflection of this harder and low-creep material. This structure overcomes the viscoelastic limitations previously encountered and creates a versatile space for potential integration of remote powering and wireless communication units or vibration and kinematics sensors [19]. The device is an interesting surgical and diagnostic tool that could improve surgery quality and provide follow-up information. Furthermore, this implementation leads to a surgically non-disruptive insert 850649-61-5 IC50 in which the surface and behavior are not modified, hence potentially fostering its 850649-61-5 IC50 acceptance. 2.?Sensor Design, Fabrication and Packaging The device presented here integrates two force sensing gauges to measure forces separately in each condyle compartment of a total condylar prosthesis. The strain gauges are placed 15.5 mm away from the center of the intercondylar fossa under the condyle. They are positioned under the contact points between.