Local plantar pressure relief in therapeutic footwear: design guidelines from finite element models

Erdemir, Ahmet; Saucerman, Jeffrey J.; Lemmon, David; Loppnow, Bryan; Turso, Brie; Ulbrecht, Jan S.; Cavanagh, Peter Re

doi:10.1016/j.jbiomech.2004.09.009

« Previous Next »Journal of Biomechanics
Volume 38, Issue 9 , Pages 1798-1806, September 2005

Local plantar pressure relief in therapeutic footwear: design guidelines from finite element models

Ahmet Erdemir
- Department of Biomedical Engineering/ND20, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
Jeffrey J. Saucerman
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA
David Lemmon
- The Methodology Center, The Pennsylvania State University, University Park, PA 16802, USA
Bryan Loppnow
- Center for Locomotion Studies, The Pennsylvania State University, University Park, PA 16802, USA
Brie Turso
- Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA
Jan S. Ulbrecht
- Departments of Biobehavioral Health and Medicine, The Pennsylvania State University, University Park, PA 16802, USA
Peter Re Cavanagh
- Department of Biomedical Engineering/ND20, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
- Orthopaedic Research Center, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA
- Corresponding author. Tel.: 2164456980; fax: 2164456083.

Accepted 2 September 2004. published online 23 November 2004.

Abstract

A major goal of therapeutic footwear in patients with pain or those at risk for skin injury is to relieve focal loading under prominent metatarsal heads. One frequent approach is to place plugs of compliant material into the midsole of the shoe. This study investigated 36 plug designs, a combination of three materials, six geometries, and two placements using a two-dimensional (2D) finite element model. Realistic loading conditions were obtained from plantar pressures (PP) recorded during walking in five subjects who wore control midsoles manufactured using Microcell Puff. Measured peak pressures underneath the second metatarsal head were similar to the results of the control model. PP obtained from simulations with the plugs built into a firm midsole were compared to the simulation results of the control midsole. Large plugs (e.g. 40mm width), made out of Microcell Puff Lite or Plastazote Medium, placed at peak pressure sites, resulted in highest reductions in peak pressures (18–28%). Smaller plugs benefited from tapering when placed at high pressure areas. Case studies were completed on a healthy male subject and a diabetic female patient to address the efficacy of a plug design favored by our simulations (pressure based placement, 40×20mm, Plastazote Medium). Successful reductions of second metatarsal head pressures were observed with a mediolateral load redistribution that was not represented by our model. 2D computer simulations allowed systematic investigation of plug properties without the need for high volume experimentation on human subjects and established basic guidelines for plug selection. In particular, plugs that are placed based on plantar pressure measurements were proven to be more effective when compared to those positioned according to the projection of the bony landmark on the foot-shoe plantar contact area.

Keywords: Footwear, Insole, Midsole, Soft tissue, Plantar pressure, Finite element model