Biomechanical analysis of different levels of constraint in TKA during daily activities

Abstract

Background Numerous total knee prosthetic implants are currently available on the orthopedic market, and this variety covers a set of different levels of constraint: among the various models available, a significant role is covered by mobile bearing cruciate-retaining design with an ultra-congruent insert, mobile bearing cruciate-retaining design, fixed-bearing posterior stabilized prosthesis and fixed-bearing constrained condylar knee. A biomechanical comparative study among them could therefore be helpful for the clinical decision-making process. This study aimed to compare the effect of these different levels of constraint in the knee biomechanics of a patient, in three different configurations representing the typical boundary conditions experienced by the knee joint during daily activities. Method The investigation was performed via finite element analysis with a knee model based on an already published and validated one. Four different types of prosthesis designs were analyzed: two mobile-bearing models and two fixed-bearing models, each one having a different level of constraint. The different designs were incorporated in to the 3D finite element model of the lower leg and analyzed in three different configurations reproducing the landing and the taking-off phases occurring during the gait cycle and chair-rising. Implant kinetics (in terms of polyethylene contact areas and contact pressure), polyethylene and tibial bone stresses were calculated under three different loading conditions for each design. Results The tibial stress distribution in the different regions of interest of the tibia remains relatively homogeneous regardless of the type of design used. The main relevant difference was observed between the mobile and fixed-bearing models, as the contact areas were significantly different between these models in the different loading conditions. As a consequence, significant changes in the stress distribution were observed at the interface between the prosthetic components, but no significant changes were noted on the tibial bone. Moreover, the different models exhibited a symmetrical medial and lateral distribution of the contact areas, which was not always common among all the currently available prostheses (i.e. medial pivot designs). Conclusion The changes of the prosthetic implant did not induce a big variation of the stress distribution in the different regions of the tibial bone, while they significantly changed the distribution of stress at the interface between the prosthetic components.

Application strategy of finite element analysis in artificial knee arthroplasty

“…The results showed that the contact area of the mobile-bearing prosthesis polyethylene insert was 400-800 mm 2 , while that of the fixed-bearing prosthesis polyethylene insert was 200-250 mm 2 . The findings confirmed that the contact area of the tibiofemoral joint of the mobile-bearing prosthesis was higher than that of the fixedbearing prosthesis; thus, the contact stress of the mobile-bearing prosthesis was lower than that of the fixed-bearing prosthesis because the contact pressure was inversely proportional to the contact area Castellarin et al (2023) (Table 1). Stukenborg-Colsman et al (2002) performed an FEA study on cadavers and reached the same conclusion: compared with fixed-bearing prostheses, mobile-bearing prostheses maximized the contact area of the tibiofemoral joint and reduced the peak contact pressure, so that the mobile-bearing prosthesis polyethylene insert provides more movement for the prosthesis and minimizes polyethylene wear compared to the fixed-bearing prosthesis model (Heesterbeek et al, 2018;Andreani et al, 2020), resulting in improved implant survival and performance.…”

“…However, biomechanical problems such as prosthesis loosening, periprosthetic fracture and prosthesis wear after knee arthroplasty remain to be solved ( Wang et al, 2021 ). At present, FEA models can be observed at any angle, and operations on the model, such as determining the osteotomy thickness, analysing the stress of different prosthetic materials ( Castellarin et al, 2023 ), and measuring the alignment between prostheses, can be simulated. FEA methods can overcome the shortcomings of traditional mechanical research methods, such as the long cycles, non-repeatable operations and high costs.…”

Survivorship and complications of cementless compared to cemented posterior-stabilized total knee arthroplasties: A systematic review and meta-analysis

“…However, these studies mainly report the results of unconstrained prostheses. Among the different types of TKA, posterior-stabilized (PS) constraints TKA is popular due to its potential for increased stability [11]. Currently, it is one of the most widely implanted TKA, representing 20%-50% of implants in implant registries [2,3].…”

“…Currently, it is one of the most widely implanted TKA, representing 20%-50% of implants in implant registries [2,3]. The posterior-stabilized designs are classified as partially constrained compared to cruciate retaining implants, as they aim to substitute the PCL with a post-cam system to provide a more stable component interface [11]. PS TKA has demonstrated excellent lifetime survivorship in cemented TKA.…”

“…PS TKA has demonstrated excellent lifetime survivorship in cemented TKA. The main issue when using these prostheses lies in the contact occurring at the post-cam interface, which causes polyethylene wear at the level of the cam mechanism and results in higher stress on the polyethylene insert itself [11]. Therefore, the use of a PS design in cementless TKA remains controversial due to unpredictable results from stresses placed on the tibial interface from the cam/post interaction.…”