An Investigation of Shock-Absorbing Prosthetic Components

Steven A. Gard, PhD and Dudley S. Childress, PhD, Principle Investigators

Student Investigator:
Sara R. Koehler, MS

Co-Investigators:
Margrit R. Meier, PhD and Rebecca Stine, MS

Funded by: Department of Veterans Affairs (DVA)

Purpose

One of the primary functions of the locomotor unit is to minimize impact forces exerted on the body during the loading response phase of gait (Ref 1).  The lower limb manages these forces through a combination of anatomical shock absorbers, which include soft tissue compression of the heel and relative joint motion at the ankle, knee, hip, and pelvis.  However, persons with transfemoral amputations lack many of these anatomical shock absorbers and, despite slower walking speeds, may be susceptible to gait deviations and higher impact forces on their intact limb and on their prosthetic side at joints proximal to their amputation (Refs 2-4).  To address this issue, shock-absorbing components (SAC) have been designed to decrease the overall stiffness of the prosthetic limb.  The purpose of this study was to compare the effect of a shock-absorbing pylon (SAP) to a stance flexion knee unit on the gait of ten transfemoral amputees. We were particularly interested in relating perceptions of increased comfort with changes in quantitative gait data associated with shock absorption and walking performance.  Ideally, the results from this study will help establish guidelines for prosthetists who fit these components on persons with transfemoral amputations and guide innovations for future SAC designs.

Methodology

The experimental protocol for this study consisted of three gait evaluations in which subjects walked with their conventional prosthesis (baseline), a SAP (Endolite TT Pylon), and a stance flexion knee unit (Otto Bock 3R60 EBS Knee).  During each gait evaluation, subjects were asked to walk over a range of five self-selected speeds.  Subjects were also asked to complete an in-house questionnaire that addressed their perceptions of comfort with each SAC.

References

(1) Perry J. Gait Analysis: Normal and Pathological Function. Thorofare, NJ: SLACK Inc., 1992.

(2) Voloshin A, et al. Force wave transmission through the human locomotor system. J Biomech Eng 1981; 103:1: 48-50.

(3) Snyder RD, et al. The effect of five prosthetic feet on the gait and loading of the sound limb in dysvascular below-knee amputees. J Rehabil Res Dev 1995; 32:4: 309-15.

(4) Ratcliffe RJ, Holt KG. Low frequency shock absorption in human walking. Gait & Posture 1997; 5:93-100.

Related Publications

Koehler, S.R., Gard, S.A., Meier, M.R., Cassar, M., Lipschutz, R. "Stance-Phase Knee Flexion in Persons with Unilateral Transfemoral Amputations Walking on an Otto Bock 3R60 EBS Knee: A Preliminary Report."  9th Annual Meeting, Gait & Clinical Movement Analysis Society, April 21-24, Lexington, KY, USA, 2004.

Koehler, S.R., Gard, S.A., Meier, M.R. "An Investigation of Shock-Absorbing Components in Persons with Unilateral Transfemoral Amputations." 11th World Congress, International Society for Prosthetics & Orthotics, August 1-6, Hong Kong, 2004.

Koehler, S.R., Gard, S.A., Meier, M.R.  "An Investigation of Shock-Absorbing Components in Persons with Unilateral Transfemoral Amputations."  31st Annual Meeting, The American Academy of Orthotists and Prosthetists (AAOP) and The Association of Children’s Prosthetic-Orthotic Clinics (ACPOC), March 16-19, Orlando, FL, USA, 2005.

Koehler, S.R., Gard, S.A., Meier, M.R.  "The Effect of Shock-Absorbing Prosthetic Components on Ground Reaction Force Profiles in Persons with Transfemoral Amputations."  10th Annual Meeting, Gait & Clinical Movement Analysis Society, April 6-9, Portland, OR, USA, 2005.