Category: Limb Restoration Rehabilitation; Technology (e.g. robotics, assistive technology, mHealth)
Objective : To determine the relationship between prosthetic foot stiffness and perception of foot stiffness, intact knee loading, and foot-ankle biomechanics during walking in unilateral transtibial amputees.
Design : Randomized single-blinded crossover trial
Setting : Laboratory setting in VA Medical Center
Participants (or Animals, Specimens, Cadavers) : A volunteer sample of 17 male, ambulatory, transtibial amputees (49±14 years old) with well-fitting prostheses, and without other neuromusculoskeletal comorbidities were enrolled and completed the study.
Each participant was fit in a randomized order with three different stiffness category Ossur Vari-flex commercially available prosthetic feet (i.e., one at the prescribed stiffness category, and one each at a level stiffer, and a level softer). Participants wore each prosthetic foot with their prescribed socket in the community for a two-week accommodation period prior to data collection.
Main Outcome Measure(s) :
Self-reported perception of prosthetic foot stiffness was collected on a 1-5 Likert scale. Peak intact knee adduction moment (IKAM) and prosthetic foot biomechanical variables (roll-over radius and ankle push-off work) were determined via data collected with a motion capture system and force plates.
Results : Increased prosthetic foot stiffness was associated with increased roll-over radius (p = 0.002), and decreased prosthetic ankle push-off work (p = 0.005). Prosthetic foot stiffness was not associated with peak IKAM (p = 0.860). Finally, there was no correlation between prosthetic foot stiffness category and perceived stiffness rating (p = 0.939).
Conclusions : Although varying the stiffness of commercial prosthetic feet objectively alters prosthetic foot-ankle variables during walking, prosthetic users are not able to correctly perceive differences in stiffness between feet. These findings have potential implications for prosthetic foot prescription decision making.
Elizabeth Halsne– Prosthetist Orthotist, University of Washington, Seattle, Washington
Joseph Czerniecki– Professor, VA Puget Sound Health Care System and University of Washington, Seattle, Washington
David Morgenroth– Associate Professor, VA Puget Sound Health Care System and University of Washington, Seattle, Washington