Force analysis of three-dimensional finite element models for single radius and multi radius prostheses during flexion and extension in total knee arthroplasty

Abstract

BACKGROUND: For patients with end-stage knee osteoarthritis, total knee arthroplasty is often necessary in clinical practice to address issues such as pain and limited mobility. Although knee replacement surgery has achieved good clinical results in treating severe osteoarthritis, there is still controversy over the clinical efficacy of single radius and multi radius prostheses. OBJECTIVE: To compare the stress characteristics of single radius and multi radius prostheses at different flexion angles in total knee arthroplasty using finite element analysis, and provide a basis for clinical selection. METHODS: Based on normal adult CT data, a three-dimensional skeletal model was established and optimized using Mimics, Geomagic, and SolidWorks. Single radius and multi radius prostheses were assembled, and the 0°-120° flexion state was simulated in Ansys. The peak von Mises stress was used as the observation index to observe the Mises stress distribution and contact area on the tibial prosthesis. RESULTS AND CONCLUSION: (1) In the range of 0°-90°, the contact stress on the tibial insert of both single radius and multi radius prostheses increased with increasing flexion angle; at high flexion angles of 90°-120°, the stress of the multi radius prosthesis gradually decreased, while that of the single radius prosthesis slightly increased. (2) At 0° flexion, the posterior capsular stress of the single radius prosthesis was lower than that of the multi radius prosthesis. (3) In the low and medium flexion range of 0°-90°, the contact area gradually decreased with increasing flexion angle for both prostheses, and the contact area on the polyethylene insert of the single radius prosthesis was always larger than that of the multi radius prosthesis. (4) Both single radius and multi radius knee prostheses can meet clinical needs well; clinically, the appropriate femoral prosthesis should be selected based on patient age, activity level, and functional requirements.

1. Introduction

Knee osteoarthritis is a chronic progressive disease characterized by knee pain, swelling, and even deformity. Total knee arthroplasty (TKA) can significantly relieve pain and restore joint function, and is an effective treatment for end-stage knee osteoarthritis, rheumatoid arthritis, and other knee diseases. With advances in surgical techniques and prosthesis design, the long-term survival rate of TKA has exceeded 90%. However, more than 5% of TKA patients undergo revision surgery within 10 years, mainly due to aseptic loosening (29.8%), infection (14.8%), and pain (9.5%). Except for joint infections, these causes are associated with changes in the mechanical environment within the joint after TKA.

Current efforts to improve patient satisfaction and functional recovery focus on designing implants that mimic the kinematics and geometry of the healthy knee, while ensuring normal use during routine physical activities. The impact of prosthesis design differences on postoperative biomechanical performance remains a clinical focus. Currently, femoral component designs are mainly classified into single radius and multi radius types, with debates centering on knee flexion stability and clinical outcome differences.

Numerous studies have compared single radius and multi radius femoral designs in TKA. Some suggest that single radius designs lead to better clinical and functional outcomes, while others report no significant difference, and some even indicate that multi radius designs may achieve superior clinical results. Theoretically, due to biomechanical advantages, single radius designs may result in less anterior knee pain. However, literature reviews show a lack of objective data on the impact of single radius prostheses on anterior knee pain after TKA. Finite element analysis, as an important biomechanical research tool, can simulate stress distribution under dynamic loading in vitro, overcoming limitations of cadaveric experiments and clinical follow-up. Therefore, this study aims to compare the biomechanical differences between single radius and multi radius prostheses over a 0°-120° flexion range using three-dimensional finite element modeling, focusing on stress distribution and contact area changes on the tibial insert. Using CT data from Asian volunteers and clinical osteotomy standards, a high-precision finite element model including subchondral bone and posterior capsule was established to more realistically simulate the postoperative mechanical environment. The findings are expected to provide a theoretical basis for personalized prosthesis selection in Asian populations and to inform prosthesis design optimization.