0
Technical Briefs

Biomechanical Validation of Finite Element Models for Two Silicone Metacarpophalangeal Joint Implants

[+] Author and Article Information
A. I. Hussein

Department of Mechanical and Industrial Engineering, Engineering Mechanics and Design Laboratory, University of Toronto, Toronto, ON, M5S 3G8, Canada; Department of Mechanical Engineering, Boston University, 110 Cummington Street, Boston, MA 02215amirah@bu.edu

J. C. Stranart

Department of Mechanical and Industrial Engineering, Engineering Mechanics and Design Laboratory, University of Toronto, Toronto, ON, M5S 3G8, Canada; University of Toronto, 63 Norgrove Crescent, Toronto, ON, M9P 3C7, Canadajcstranart@hotmail.com

S. A. Meguid

Department of Mechanical and Industrial Engineering, Engineering Mechanics and Design Laboratory, University of Toronto, Toronto, ON, M5S 3G8, Canada; Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, ON, M5S 3G8, Canadameguid@mie.utoronto.ca

E. R. Bogoch1

Department of Surgery, University of Toronto, Toronto, ON, M5C 1R6, Canada; Li Ka Shing Knowledge Institute and the Mobility Program Clinical Research Unit, St. Michael’s Hospital, Toronto, ON, M5C 1R6, Canadabogoche@smh.ca

1

Corresponding author. 55 Queen Street East, Suite 800, Toronto, ON, M5C 1R6, Canada.

J Biomech Eng 133(2), 024501 (Jan 31, 2011) (6 pages) doi:10.1115/1.4003311 History: Received February 03, 2010; Revised December 19, 2010; Posted December 22, 2010; Published January 31, 2011; Online January 31, 2011

Silicone implants are used for prosthetic arthroplasty of metacarpophalangeal (MCP) joints severely damaged by rheumatoid arthritis. Different silicone elastomer MCP implant designs have been developed, including the Swanson and the NeuFlex implants. The goal of this study was to compare the in vitro mechanical behavior of Swanson and NeuFlex MCP joint implants. Three-dimensional (3D) finite element (FE) models of the silicone implants were modeled using the commercial software ANSYS and subjected to angular displacement from 0 deg to 90 deg. FE models were validated using mechanical tests of implants incrementally bent from 0 deg to 90 deg in a joint simulator. Swanson size 2 and 4 implants were compared with NeuFlex size 10 and 30 implants, respectively. Good agreement was observed throughout the range of motion for the flexion bending moment derived from 3D FE models and mechanical tests. From 30 deg to 90 deg, the Swanson 2 demonstrated a greater resistance to deformation than the NeuFlex 10 and required a greater bending moment for joint flexion. For larger implant sizes, the NeuFlex 30 had a steeper moment-displacement curve, but required a lower moment than the Swanson 4, due to implant preflexion. On average, the stress generated at the implant hinge from 30 deg to 90 deg was lower in the NeuFlex than in the Swanson. On average, starting from the neutral position of 30 deg for the preflexed NeuFlex implant, higher moments were required to extend the NeuFlex implants to 0 deg compared with the Swanson implants, which returned spontaneously to resting position. Implant toggling within the medullary canals was less in the NeuFlex than in the Swanson. The differential performance of these implants may be useful in implant selection based on the preoperative condition(s) of the joint and specific patient functional needs.

FIGURES IN THIS ARTICLE
<>
Copyright © 2011 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Diagram of joint simulator designed for this study to test flexible MCP joint implants. (A) Implant is held in a plaster-filled tube and (B) the metacarpal end is clamped in place. (C)The proximal phalanx is rotated incrementally throughout the range of motion using (D) a stepper motor. A pin attached to (B) the metacarpal casing provides contact with (E) the force sensor. Digital image correlation was used to track the position of landmarks (“x”) in order to calculate the moment arms and flexion angle.

Grahic Jump Location
Figure 2

Forces acting on the metacarpal stem of the implants in the MCP joint simulator. The proximal stem was clamped via the tube holder shown in Fig. 1 after each flexion/extension displacement increment. FN=normal reaction force at sensor; Ff=friction force; R, r1, and r2=moment arms; and mg=weight of the tube and its contents. The bending moment required to flex the implants was calculated using MB=FNR±mgr1±Ffr2.

Grahic Jump Location
Figure 3

Comparison of the flexion angle versus the magnitude (not polarity/direction) of the bending moment from the three-dimensional finite element analysis and the mechanical test for (a) the smaller Swanson 2 (SW2) and NeuFlex 10 (NF10) implants, and (b) the larger Swanson 4 (SW4) and NeuFlex 30 (NF30) implants. The bending moment for flexion as calculated by three-dimensional finite element analysis demonstrated good agreement with the mechanical tests over the entire range of motion. The NeuFlex implants required less bending moment to flex over the functional range of motion for activities of daily living (33–73 deg) than the Swanson implants.

Grahic Jump Location
Figure 4

Comparison of implant behavior based on three-dimensional finite element analysis over the entire ROM: (a) the maximum von Mises stress in the hinge region of the Swanson 2 and NeuFlex 10 implants and (b) the maximum von Mises stress in the hinge region of the Swanson 4 and NeuFlex 30 implants. The NeuFlex 10 implant had lower stresses than the Swanson 2 implant from 20 deg to 78 deg. The NeuFlex 30 implant had lower stresses than the Swanson 4 implant from 18 deg to 68 deg. At high flexion angles, stress in the Swanson implant was less than in the NeuFlex implant.

Grahic Jump Location
Figure 5

von Mises stress distribution in the hinge region at 70 deg flexion angle in (a) sectioned Swanson 2 implant and (b) sectioned NeuFlex 10 implant. The maximum von Mises stresses were localized at the inner hinge region off the symmetry plane in the Swanson implant. The NeuFlex implant demonstrated maximum von Mises stresses at the volar side during flexion at the symmetry plane. NeuFlex implants demonstrated a smaller volume of high stress regions.

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In