Mechanical performance of cementless total knee replacements: It is not all about the maximum loads

Abstract

Finite element (FE) models are frequently used to assess mechanical interactions between orthopedic implants and surrounding bone. However, FE studies are often limited by the small number of bones that are modeled; the use of normal bones that do not reflect the altered bone density distributions that result from osteoarthritis (OA); and the application of simplified load cases usually based on peak forces and without consideration of tibiofemoral kinematics. To overcome these limitations, we undertook an integrated approach to determine the most critical scenario for the interaction between an uncemented tibial component and surrounding proximal tibial bone. A cementless component, based on a modern design, was virtually implanted using computedtomography scans from 13 patients with knee OA. FE simulations were performed across a demanding activity, stair ascent, by combining in vivo experimental forces from the literature with tibiofemoral kinematics measured from patients who had received the same design of knee component. The worst conditions for the bone-implant interaction, in terms of micromotion and percentage of interfacial bone mass at risk of failure, did not arise from the maximum applied loads. We also found large variability among bones and tibiofemoral kinematics sets. Our results suggest that future FE studies should not focus solely on peak loads as this approach does not consistently correlate to worst-case scenarios. Moreover, multiple load cases and multiple bones should be considered to best reflect variations in tibiofemoral kinematics, anatomy, and tissue properties. ß

Effect of varus alignment on the bone‐implant interaction of a cementless tibial baseplate during gait

“…Interestingly, the increase in micromotion (79% for total and 37% for shear) was larger than the 22% increase in the varus‐valgus joint moment (from 27.7 to 33.7 Nm). Our findings are consistent with prior studies that found that the worst‐case scenario for the bone‐implant interaction involves submaximal loads 20–22,32 . Moreover, our values of shear micromotion are within the range 26 to 63 µm found experimentally by Chong et al 20 …”

Multiacquisition Variable-Resonance Image Combination Magnetic Resonance Imaging to Study Detailed Bone Apposition and Fixation of Cementless Knee System Compared to Cemented Total Knee Replacements

“…However, aseptic loosening continues to be the leading cause of revision for TKA, accounting for 31%-39% of revision cases [ 1 , 2 ]. Cement fixation provides robust initial fixation; however, it is subject to tensile and shear forces, which are not well tolerated and can lead to micromotion and component loosening [ 25 , 26 ]. Cementless fixation provides the opportunity for biologic ingrowth with the potential for long-term remodeling and eliminates the risk of cement particle third-body debris [ 25 , 26 ].…”

“…Cement fixation provides robust initial fixation; however, it is subject to tensile and shear forces, which are not well tolerated and can lead to micromotion and component loosening [ 25 , 26 ]. Cementless fixation provides the opportunity for biologic ingrowth with the potential for long-term remodeling and eliminates the risk of cement particle third-body debris [ 25 , 26 ]. This biologic fixation may lower the incidence of aseptic loosening and could provide a superior option for patients most at risk of loosening, namely young and obese patients [ 27 , 28 ].…”

Biomechanical evaluation of total ankle arthroplasty. Part II: Influence of loading and fixation design on tibial bone–implant interaction

“…These load conditions are not representative of the complex and dynamic loading environment at the ankle during daily activities, which includes multiaxial forces and moments. In other implant systems, such as the tibial component of total knee arthroplasty, the most critical scenario for the interaction between the implant and the bone has been shown to be the result of complex combinations of submaximal loads and relatively high multiaxial moments 9–12 . Thus, even though McInnes et al 7 and Sopher et al 8 showed that different fixation designs respond differently to applied loads, it remains unclear how these same fixation designs would behave under the complex loading scenarios.…”