Shock absorption during transtibial amputee gait: Does longitudinal prosthetic stiffness play a role?
BACKGROUND
Reduced-stiffness components are often prescribed in lower-limb prostheses, but their efficacy in augmenting shock absorption has been inconclusive.


OBJECTIVE
To perform a systematic variation of longitudinal prosthetic stiffness over a wide range of values and to evaluate its effect on shock absorption during gait.


METHODS
Repeated-measures crossover experiment.


METHODS
Twelve subjects with a unilateral transtibial amputation walked at normal and fast self-selected speeds. Longitudinal prosthetic stiffness was modified by springs within a shock-absorbing pylon: normal (manufacturer recommended), 75% of normal (medium), 50% of normal (soft), and rigid (displacement blocked). The variables of interest were kinematic (stance-phase knee flexion and pelvic obliquity) and kinetic (prosthetic-side ground reaction force loading peak magnitude and timing).


RESULTS
No changes were observed in kinematic measures during gait. A significant difference in peak ground reaction force magnitudes between medium and normal ( p = 0.001) during freely selected walking was attributed to modified walking speed ( p = 0.008). Ground reaction force peaks were found to be statistically different during fast walking, but only between isolated stiffness conditions. Thus, altering longitudinal prosthesis stiffness produced no appreciable change in gait biomechanics.


CONCLUSIONS
Prosthesis stiffness does not appear to substantially influence shock absorption in transtibial prosthesis users. Clinical relevance Varying the level of longitudinal prosthesis stiffness did not meaningfully influence gait biomechanics at self-selected walking speeds. Thus, as currently prescribed within a transtibial prosthesis, adding longitudinal stiffness in isolation may not provide the anticipated shock absorption benefits. Further research into residual limb properties and compensatory mechanisms is needed.
1 Northwestern University Prosthetics-Orthotics Center, Chicago, IL, USA.
Erin
E
Boutwell
1 Northwestern University Prosthetics-Orthotics Center, Chicago, IL, USA.|2 Jesse Brown VA Medical Center, Chicago, IL, USA.
Rebecca
R
Stine
1 Northwestern University Prosthetics-Orthotics Center, Chicago, IL, USA.|2 Jesse Brown VA Medical Center, Chicago, IL, USA.
Steven
S
Gard
D000054:Acceleration; D000328:Adult; D000368:Aged; D000674:Amputees / Q000534:rehabilitation*; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D005684:Gait / Q000502:physiology*; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D017755:Prosthesis Fitting / Q000379:methods; D012307:Risk Factors; D013314:Stress, Mechanical
Biomechanics of prosthetic/orthotic devices; gait analysis; testing of prosthetic and orthotic components