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

Abstract

The increase in the number of revision surgeries after a total knee replacement surgery reaches 19%. One of the reasons for the majority of revisions relates to the debris of the ultra-high molecular weight polyethylene that serves to facilitate the sliding between the femoral and tibial components. This paper addresses the biomechanical properties of ULTEM^TM 1010 in a totally new knee replacement design, based on one of the commercial models of the Stryker manufacturer. It is designed and produced through additive manufacturing that replaces the tibial component and the polyethylene in such a way as to reduce the pieces that are part of the prosthetic assembly to only two: the femoral and the tibial (the so-called "two-component knee prosthesis"). The cytotoxicity as well as the live/dead tests carried out on a series of biomaterials guarantee the best osteointegration of the studied material. The finite element simulation method guarantees the stability of the material before a load of 2000 N is applied in the bending angles 0°, 30°, 60°, 90°, and 120°. Thus, the non-metallic prosthetic material and approach represent a promising alternative for metal-allergic patients.

Keywords: ULTEMTM 1010 biomaterial; additive manufacturing; biomechanical design; live/dead; non-metallic knee prosthesis; two-component knee prosthesis.

Figure 1

Some parts of cemented knee prothesis, from left to right: femoral component, polyethylene, tibia component [31].

Figure 2

Characteristics of the new bicomponent knee prosthesis proposal.

Figure 3

Parts manufactured by FDM technology: (a) femoral part; (b) tibial part; (c) 1BA specimens for tensile tests (XY-XZ-YZ orientation).

Figure 4

Bending angles considered in the analysis.

Figure 5

Main characteristics considered in the pre-processor: (a) contact properties; (b) definition of the fixation; (c) definition of the applied force.

Figure 6

Penetration assay in the bone: (a) pork bone used; (b) skewer geometry; (c) section of the cancellous bone where the skewers will be inserted.

Figure 7

Experimentally measured mechanical properties: (a) tensile modulus, E; (b) tensile stress, σ; (c) stress–strain averaged curves XY, XZ, YZ.

Figure 8

Results of the FEM simulation. (Top) Stress frictional (lower femoral part viewpoint of the observer), shear stress and von Mises stress (top tibial part viewpoint of the observer) to flexion angles 0°; 30°;60°. (Bottom) Penetration contact and shear stress to 90°;120°.

Figure 9

Ratio of live/dead cells of the biomaterials after 7 days.

Figure 10

Penetration assay images and fixation of skewers to the bone: (a) skewers driven into cancellous bone; (b) orthogonal views of the exposure to RX. Top view) Holes formed by the skewers are represented and one of them is sectioned by AA’ cutting plane. AA’ View) Sectional representation that indicates the height of the skewer.