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BACKGROUND: Lower limb amputees have a high incidence of comorbidities, such as osteoarthritis, which are believed to be caused by kinetic asymmetries. A lack of prosthetic adaptation to different terrains requires kinematic compensations, which may influence these asymmetries. METHOD: Six SIGAM grade E-F trans-tibial amputees (one bilateral) wore motion capture markers while standing on force plates, facing down a 5° slope. The participants were tested under three prosthetic conditions; a fixed attachment foot (FIX), a hydraulic ankle (HYD) and a microprocessor foot with a 'standing support' mode (MPF). The resultant ground reaction force (GRF) and support moment for prosthetic and sound limbs were chosen as outcome measures. These were compared between prosthetic conditions and to previously captured able-bodied control data. RESULTS: The distribution of GRF between sound and prosthetic limbs was not significantly affected by foot type. However, the MPF condition required fewer kinematic compensations, leading to a reduction in sound side support moment of 59% (p=0.001) and prosthetic side support moment of 43% (p=0.02) compared to FIX. For the bilateral participant, only the MPF positioned the GRF vector anterior to the knees, reducing the demand on the residual joints to maintain posture. CONCLUSIONS: For trans-tibial amputees, loading on lower limb joints is affected by prosthetic foot technology, due to the kinematic compensations required for slope adaptation. MPFs with 'standing support' might be considered reasonable and necessary for bilateral amputees, or amputees with stability problems due to the reduced biomechanical compensations evident.
RESUMEN
INTRODUCTION: Asymmetrical limb loading is believed to cause health problems for lower limb amputees and is exacerbated when walking on slopes. Hydraulically damped ankle-feet improve ground compliance on slopes compared to conventional prosthetic feet. Microprocessor-controlled hydraulic ankle-feet provide further adaptation by dynamically adjusting viscoelastic damping properties. METHOD: Using a case series design, gait analysis was performed with four trans-tibial amputees. There were two walking conditions (ramp ascent and descent) and two prosthetic foot conditions (microprocessor-control on and off - MPF-on and MPF-off). Total support moment integral ( M I sup ) and degree-of-asymmetry were compared across foot conditions. RESULTS: During ramp descent, the transition of prosthetic ankle moment from dorsiflexion to plantarflexion occurred earlier in stance phase with MPF-on, slowing the angular velocity of the shank. During ramp ascent, the MPF-on dorsiflexion/plantarflexion moment transition occurred later, meaning less resistance to shank rotation in early stance and increasing walking speed by up to 6%. For both slope conditions, sound limb M I sup was universally decreased with MPF-on (4-13% descent, 3-11% ascent). DISCUSSION: Microprocessor-control of hydraulic ankle-feet reduced the total loading of the sound limb joints, for both walking conditions, for all participants. This may have beneficial consequences for long-term joint health and walking efficiency.
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INTRODUCTION: Trans-femoral amputees are at risk of musculoskeletal problems that are in part caused by loading asymmetry during activities, such as prolonged standing, particularly on uneven or sloped ground. METHODS: Four prosthetic conditions were tested; microprocessor knee 'standing support' mode activated (ON) and deactivated (OFF), combined with a rigidly attached foot (RA) and with an articulating, hydraulic ankle-foot (HA). Five trans-femoral amputees and five able-bodied controls were measured using a motion capture system and a force plate while standing, facing down a 5° slope. Ground reaction force distributions and centre-of-pressure root-mean-square (COP RMS) were calculated as outcome measures. RESULTS: Compensatory kinematic adjustments were observed for RA conditions but not for HA conditions. HA-OFF reduced ground reaction force degree-of-asymmetry for all five amputees, compared to RA-OFF. RA-ON reduced ground reaction force degree-of-asymmetry for four amputees, compared to RA-OFF. In terms of balance, the HA conditions reduced the mean inter-limb COP RMS by 24-25% compared to equivalent RA conditions, while ON conditions reduced it by 9-11%, compared to equivalent OFF conditions. CONCLUSIONS: It is important to consider both prosthetic knee and ankle technologies when prescribing devices to trans-femoral amputees. The combination of hydraulic ankle and knee standing support technologies produced outcomes closest to normal biomechanics.
RESUMEN
Most clinically available prosthetic feet have a rigid attachment or incorporate an "ankle" device allowing elastic articulation during stance, with the foot returning to a "neutral" position at toe-off. We investigated whether using a foot with a hydraulically controlled articulating ankle that allows the foot to be relatively dorsiflexed at toe-off and throughout swing would increase minimum toe clearance (MTC). Twenty-one people with unilateral transtibial amputation completed overground walking trials using their habitual prosthetic foot with rigid or elastic articulating attachment and a foot with a hydraulic ankle attachment (hyA-F). MTC and other kinematic variables were assessed across multiple trials. When using the hyA-F, mean MTC increased on both limbs (p = 0.03). On the prosthetic limb this was partly due to the device being in its fully dorsiflexed position at toe-off, which reduced the "toes down" foot angle throughout swing (p = 0.01). Walking speed also increased when using the hyA-F (p = 0.001) and was associated with greater swing-limb hip flexion on the prosthetic side (p = 0.04), which may have contributed to the increase in mean MTC. Variability in MTC increased on the prosthetic side when using the hyA-F (p = 0.03), but this did not increase risk of tripping.