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Biomechanical Efficacy of Shear-Reducing Diabetic Insoles

Elaborations on Future Design Criteria

Yavuz, Metin, DEng; Ersen, Ali, PhD; Richardson, Mike, PT, DPT; Adams, Linda S., BSME; Holmes, Clayton F., PT, EdD, MS, ATC; Wijesundara, Muthu B.J., PhD; Wukich, Dane K., MD; La Fontaine, Javier, DPM, MS

JPO: Journal of Prosthetics and Orthotics: April 2019 - Volume 31 - Issue 2 - p 82–86
doi: 10.1097/JPO.0000000000000241
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Introduction Increasing evidence suggests that plantar shear forces and related stresses play a major role in diabetic foot ulcerations. Several orthotic devices are commercially available to reduce plantar shear forces within the shoe. The biomechanical efficacy of these devices was not tested in vivo. To measure spatiotemporal characteristics of gait to assess the efficacy of such shear-reducing insoles (SRIs), control insoles were also tested for comparison purposes.

Material and Methods Eighteen healthy volunteers walked along a 30.5-m line while wearing three types of insoles in randomized order. Spatiotemporal parameters of gait were quantified. Statistical comparisons between the control and SRIs were conducted using repeated measures analysis of variance. Intraclass correlation coefficients (ICCs) were also calculated to reveal the repeatability of the trials. Step length, gait speed, and cadence of the subjects remained similar regardless of the insole type.

Results No significant difference was observed in any variable. The ICC values revealed excellent repeatability.

Conclusions The lack of changes in gait parameters in these results suggest that shear-reducing diabetic inserts did not decrease plantar shear forces as intended. This might be caused by unrealistic in vitro testing conditions during the prototype development. Future designs should also consider friction at the lateral walls of the inserts, an increase in step repetition that accompanies a decrease in gait speed and/or step length, and a possible temperature increase within the shoe. We conclude that the future SRIs need to be redesigned based on comprehensive biomechanical guidelines.

METIN YAVUZ, DEng; ALI ERSEN, PhD; MIKE RICHARDSON, PT, DPT; and LINDA S. ADAMS, BSME, are affiliated with the Department of Physical Therapy, University of North Texas Health Science Center, Fort Worth, Texas.

CLAYTON F. HOLMES, PT, EdD, MS, ATC is affiliated with Arkansas Colleges of Health Education, Physical Therapy, Fort Smith, Arkansas.

MUTHU B.J. WIJESUNDARA, PhD, is affiliated with the University of Texas at Arlington Research Institute, Fort Worth, Texas.

DANE K. WUKICH, MD, is affiliated with the Department of Orthopaedic Surgery, University of Texas Southwestern Medical Center, Dallas, Texas.

JAVIER LA FONTAINE, DPM, MS, is affiliated with the Department of Plastic Surgery, University of Texas Southwestern Medical Center, Dallas, Texas.

Disclosure: The authors declare no conflict of interest.

Correspondence to: Metin Yavuz, DEng, Department of Physical Therapy, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, Texas 76107; email: Metin.Yavuz@unthsc.edu

© 2019 by the American Academy of Orthotists and Prosthetists.