The aim of this thesis was to determine the biomechanical adaptations made by active unilateral trans-tibial amputees when they used a prosthesis incorporating a hydraulically-damped, articulating ankle-foot device compared to non-hydraulically attached devices. Kinematic and kinetic data were recorded while participants ambulated over a flat and level surface at their customary walking speeds and at speeds they perceived to be faster and slower using the hydraulic device and their habitual foot. Use of the hydraulic device resulted in increases in self-selected walking speeds with a simultaneous reduction in intact-limb work per meter travelled. Use of the device also attenuated inappropriate fluctuations in the centre-of-pressure trajectory beneath the prosthetic foot and facilitated increased residual-knee loading-response flexion and prosthetic-limb load bearing during stance. These changes occurred despite the hydraulic device absorbing more, and returning less, energy than the participants’ habitual ankle-foot devices. The changes were present across all walking speeds but were greatest at customary walking speeds. The findings suggest that a hydraulic ankle-foot device has mechanical benefits, during overground gait, for active unilateral trans-tibial amputees compared to other attachment methods. The findings also highlight that prosthetic ankle-foot device ‘performance’ can be evaluated using surrogate measures and without modelling an ‘ankle joint’ on the prosthetic limb.

Yes / 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.

Yes / If a prosthetic foot creates resistance to forwards shank rotation as it deforms during loading, it will exert a braking effect on centre of mass progression. The present study determines whether the centre of mass braking effect exerted by an amputee's habitual rigid ‘ankle’ foot was reduced when they switched to using an ‘Echelon’ hydraulic ankle–foot device. Nineteen lower limb amputees (eight trans-femoral, eleven trans-tibial) walked overground using their habitual dynamic-response foot with rigid ‘ankle’ or ‘Echelon’ hydraulic ankle–foot device. Analysis determined changes in how the centre of mass was transferred onto and above the prosthetic-foot, freely chosen walking speed, and spatio-temporal parameters of gait. When using the hydraulic device both groups had a smoother/more rapid progression of the centre of pressure beneath the prosthetic hindfoot (p ≤ 0.001), and a smaller reduction in centre of mass velocity during prosthetic-stance (p < 0.001). As a result freely chosen walking speed was higher in both groups when using the device (p ≤ 0.005). In both groups stance and swing times and cadence were unaffected by foot condition whereas step length tended (p < 0.07) to increase bilaterally when using the hydraulic device. Effect size differences between foot types were comparable across groups. Use of a hydraulic ankle–foot device reduced the foot's braking effect for both amputee groups. Findings suggest that attenuation of the braking effect from the foot in early stance may be more important to prosthetic-foot function than its ability to return energy in late stance.

The aim of this thesis was to determine the biomechanical adaptations made by active unilateral trans-tibial amputees when they used a prosthesis incorporating a hydraulically-damped, articulating ankle-foot device compared to non-hydraulically attached devices. Kinematic and kinetic data were recorded while participants ambulated over a flat and level surface at their customary walking speeds and at speeds they perceived to be faster and slower using the hydraulic device and their habitual foot. Use of the hydraulic device resulted in increases in self-selected walking speeds with a simultaneous reduction in intact-limb work per meter travelled. Use of the device also attenuated inappropriate fluctuations in the centre-of-pressure trajectory beneath the prosthetic foot and facilitated increased residual-knee loading-response flexion and prosthetic-limb load bearing during stance. These changes occurred despite the hydraulic device absorbing more, and returning less, energy than the participants’ habitual ankle-foot devices. The changes were present across all walking speeds but were greatest at customary walking speeds. The findings suggest that a hydraulic ankle-foot device has mechanical benefits, during overground gait, for active unilateral trans-tibial amputees compared to other attachment methods. The findings also highlight that prosthetic ankle-foot device ‘performance’ can be evaluated using surrogate measures and without modelling an ‘ankle joint’ on the prosthetic limb.

Yes / Background Previous research has shown that use of a dynamic-response prosthetic foot (DRF) that incorporates a small passive hydraulic ankle device (hyA-F), provides certain biomechanical benefits over using a DRF that has no ankle mechanism (rigA-F). This study investigated whether use of a hyA-F in unilateral trans-tibial amputees (UTA) additionally provides metabolic energy expenditure savings and increases the symmetry in walking kinematics, compared to rigA-F. Methods Nine active UTA completed treadmill walking trials at zero gradient (at 0.8, 1.0, 1.2, 1.4, and 1.6 of customary walking speed) and for customary walking speed only, at two angles of decline (5° and 10°). The metabolic cost of locomotion was determined using respirometry. To gain insights into the source of any metabolic savings, 3D motion capture was used to determine segment kinematics, allowing body centre of mass dynamics (BCoM), differences in inter-limb symmetry and potential for energy recovery through pendulum-like motion to be quantified for each foot type. Results During both level and decline walking, use of a hyA-F compared to rigA-F significantly reduced the total mechanical work and increased the interchange between the mechanical energies of the BCoM (recovery index), leading to a significant reduction in the metabolic energy cost of locomotion, and hence an associated increase in locomotor efficiency (p < 0.001). It also increased inter-limb symmetry (medio-lateral and progression axes, particularly when walking on a 10° decline), highlighting the improvements in gait were related to a lessening of the kinematic compensations evident when using the rigA-F. Conclusions Findings suggest that use of a DRF that incorporates a small passive hydraulic ankle device will deliver improvements in metabolic energy expenditure and kinematics and thus should provide clinically meaningful benefits to UTAs’ everyday locomotion, particularly for those who are able to walk at a range of speeds and over different terrains. / Engineering and Physical Sciences Research Council(EPSRC, reference EP/H010491/1).