The effects of prosthetic ankle stiffness on ankle and knee kinematics, prosthetic limb loading, and net metabolic cost of trans-tibial amputee gait.
BACKGROUND
Previous studies of commercially-available trans-tibial prosthetic components have been unable to provide clear insight into the relationships between prosthetic mechanical properties and user performance (i.e., gait quality and energy expenditure), the understanding of which is key to improving prosthesis design and prescription. Many of these studies have been limited by not characterising the mechanical properties of the tested prostheses and/or only considered level walking at self-selected speeds. The aim of this study was to conduct a systematic investigation of the effects of ankle rotational stiffness on trans-tibial amputee gait during various walking conditions reflective of those encountered during daily ambulation.


METHODS
Ankle and knee kinematics, prosthetic limb normal ground reaction forces, and net metabolic cost were measured in five traumatic unilateral trans-tibial amputees during treadmill walking on the level, a 5% incline and a 5% decline whilst using an experimental articulated prosthetic foot with four different rotational stiffness setups and without changes in alignment between conditions.


RESULTS
Overall, lower dorsiflexion stiffness resulted in greater prosthetic side dorsiflexion motion and sound side knee flexion, reduced normal ground reaction force during the loading phase of prosthetic stance and reduced net metabolic cost.


CONCLUSIONS
Few differences were observed with changes in plantarflexion stiffness, most likely due to the foot achieving early foot flat. Low dorsiflexion stiffness generally improved gait performance seemingly due to easier tibial progression during stance. However, observed differences were small, suggesting that a wider range of walking and stiffness conditions would be useful to fully explore these effects in future studies.
Northwestern University Prosthetics-Orthotics Center, Northwestern University, Chicago, USA; Centre for Health Sciences Research, University of Salford, Greater Manchester, UK. Electronic address: Matthew-Major@Northwestern.edu.
Matthew J
MJ
Major
Centre for Health Sciences Research, University of Salford, Greater Manchester, UK; UNIPOD - United National Institute for Prosthetics & Orthotics Development, University of Salford, Greater Manchester, UK.
Martin
M
Twiste
Centre for Health Sciences Research, University of Salford, Greater Manchester, UK.
Laurence P J
LP
Kenney
Centre for Health Sciences Research, University of Salford, Greater Manchester, UK.
David
D
Howard
D000674:Amputees; D000843:Ankle Joint / Q000503:physiopathology*; D001186:Artificial Limbs; D001696:Biomechanical Phenomena / Q000502:physiology; D004734:Energy Metabolism; D005080:Exercise Test; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D013977:Tibia; D016474:Weight-Bearing / Q000502:physiology