Customized surface-guided knee implant: Contact analysis and experimental test

Abstract

Contact pressure and stresses on the articulating surface of the tibial component of a total knee replacement are directly related to the joint contact forces and the contact area. These stresses can result in wear and fatigue damage of the ultra-high-molecular-weight polyethylene. Therefore, conducting stress analysis on a newly designed surface-guided knee implant is necessary to evaluate the design with respect to the polyethylene wear. Finite element modeling is used to analyze the design's performance in level walking, stair ascending and squatting. Two different constitutive material models have been used for the tibia component to evaluate the effect of material properties on the stress distribution. The contact pressure results of the finite element analysis are compared with the results of contact pressure using pressure-sensitive film tests. In both analyses, the average contact pressure remains below the material limits of ultra-high-molecular-weight polyethylene insert. The peak von Mises stresses in 90° of flexion and 120° of flexion (squatting) are 16.28 and 29.55 MPa, respectively. All the peak stresses are less than the fatigue failure limit of ultra-high-molecular-weight polyethylene which is 32 MPa. The average contact pressure during 90° and 120° of flexion in squatting are 5.51 and 5.46 MPa according to finite element analysis and 5.67 and 8.14 MPa according to pressure-sensitive film experiment. Surface-guided knee implants are aimed to resolve the limitations in activities of daily living after total knee replacement by providing close to normal kinematics. The proposed knee implant model provides patterns of motion much closer to the natural target, especially as the knee flexes to higher degrees during squatting.

Biomechanical Analysis of Non-Metallic Biomaterial in the Manufacture of a New Knee Prosthesis

“…Three-dimensional parts were modeled by performing an exhaustive measurement on the real references. From the obtained models, the parts were exported to the FEM simulation tool (ANSYS/Academic Research of ANSYS Inc., Houston, PA, USA) for analysis in conformity with the ISO 14243-3: 2009 standard [33], to adapt the loading and displacement conditions according to the references [5,25,34], while considering the U1010 physical properties in replacement of UHMWPE. The physical properties of the U1010 material implemented in the simulations were collated in the tensile test described in the previous section.…”

“…The appropriate loading and boundary conditions were applied to the femoral and tibial tray components according to the ISO standard [30,35]. In this particular case, a structural static analysis was carried out for each angle considering a rough-type contact between the two parts and applying a friction coefficient of 0.04 [5,32]. It is possible to apply another type of dynamical analysis, but at first, it is intended to prove the stability, reliability, and performance of the U1010 material to external loads applied normally in this new two-component prosthesis.…”

“…The number of revision surgeries subsequent to primary knee replacement surgery is hence expected to increase. According to [5], in order to reduce the number of revisions of such interventions and to achieve lasting results, it is important to restore joint kinematics, which in turn depends on the implant design as well as on biomechanics [6,7]. The most recent designs are aimed at creating personalized prostheses for the patients.…”

“…The wear of PE is directly related to the size of the contact areas and the magnitude of the contact [25]. The wear of PE produces wear particles around the knee implant that can lead to osteolysis, which can consequently lead to the loosening of the implant in the long run [5].…”

“…Materials 2021, 14, x FOR PEER REVIEW 3 of 13 particles around the knee implant that can lead to osteolysis, which can consequently lead to the loosening of the implant in the long run [5].…”