Introduction. Both measured resection technique and gap balancing technique have been important surgical concepts in total knee arthroplasty (TKA). Modified gap technique has been reported to be beneficial for the intra-operative soft tissue balancing in
Introduction. Mid-flexion stability is believed to be an important factor influencing successful clinical outcomes in total knee arthroplasty. The post of a
Introduction. Patellar crepitus and clunk are tendofemoral-related complications predominantly associated with
Introduction. When evaluating the biomechanical performance of a total knee arthroplasty (TKA) implant design, device companies are usually required to select the “worst case scenario” for testing by the regulatory bodies. However, most test standards (e.g., ASTM, ISO) do not explicitly specify how the “worst case” should be determined. It is quite often that an extreme size (the smallest or the largest) in a system is taken as the “worst case” size. The smallest size is sometimes selected under the rationale that it has the smallest geometry thus the weakest mechanical structure. While the largest size is sometimes selected under the rationale that it is used on the biggest patients associated with the highest loads. However, implant geometry and in vivo load are two compounding factors that together determine the implant's biomechanical challenge. As the result, the true “worst case” must be determined considering both factors, and the choice could be design-specific. This study evaluated the femorotibial contact stress of a TKA implant system, and demonstrated that the extreme sizes may not simply be the “worst case”. Methods. The femorotibial contact stress of a
Introduction:. While survivorship of total knee arthroplasty (TKA) is excellent, up to 25% of patients remain dissatisfied with their outcome [1, 2]. Knee instability, which is common during high demand activities, contributes to patient dissatisfaction [3]. As younger patients undergo TKA, longevity requirements and functional demands will rise [4]. Design factors influence the functional outcome of the procedure [5, 6], although in clinical studies it can be difficult to distinguish joint mechanics differences between designs due to confounding variability in patient-related factors. The objective of the current study was to assess the stability and mechanics of several current TKA designs during high-demand dynamic activities using a computational model of the lower limb. Methods:. Three high-demand dynamic activities (gait, stepdown, squat) were simulated in a previously described lower limb model (Fig. 1) [7]. The model included calibrated tibiofemoral (TF) soft-tissue structures, patellofemoral (PF) ligaments and extensor mechanism [8]. Loading conditions for the simulations were derived from telemetric patient data in order to evaluate TKA designs under physiological kinematic and loading conditions [7, 9]. Four fixed-bearing TKA designs (both cruciate-retaining (CR) and
Introduction. Increasing attention to the functional outcome of total knee arthroplasty (TKA) has demonstrated that many patients experience limitations when attempting to perform demanding activities that are normal for age-matched peers, primarily because of knee symptoms. Episodes of instability following TKA are most commonly reported during activities in which significant transverse or torsional forces are supported by the joint with relatively low joint compression forces, including stair-descent and walking on sloped or uneven surfaces. This study was performed to examine the influence of conformity between the femoral and tibial components on the Antero-Posterior (AP) stability of knee during stair descent. Methods. Six cadaveric knees were loaded in a six degree-of-freedom joint simulator, with the application of external forces simulating the action of the quadriceps and hamstring muscles and the external loads and moments occurring during stair descent, including the stages of terminal swing phase, weight-acceptance phase (prior to and after quadriceps contraction) and mid-stance. During these manoeuvres, the displacement and rotation of the femur and the tibia were measured with a multi-camera high resolution motion analysis system (Fig. 1). Each knee was tested in the intact and ACL deficient condition – and after implantation of total knee prosthesis with Cruciate-Retaining (CR), Cruciate-Sacrificing with an intact PCL (CS + PCL), Cruciate-Sacrificing with an absent PCL (CS-PCL) and