Unilateral below-knee amputees commonly experience asymmetrical gait patterns and develop comorbidities in their intact (non-amputated) and residual (amputated) legs, with the mechanisms leading to these asymmetries and comorbidities being poorly understood. Prosthetic feet have been designed in an attempt to minimize walking asymmetries by utilizing elastic energy storage and return (ESAR) to help provide body support, forward propulsion and leg swing initiation. However, identifying the influence of walking speed and prosthetic foot stiffness on amputee gait mechanics is needed to develop evidence-based rationale for prosthetic foot selection and treatment of comorbidities. In this research, experimental and modeling studies were performed to identify the influence of walking speed and prosthetic foot stiffness on amputee walking mechanics. The results showed that when asymptomatic and relatively new amputees walk using clinically prescribed prosthetic feet across a wide range of speeds, loading asymmetries exist between the intact and residual knees. However, knee intersegmental joint force and moment quantities in both legs were not higher compared to non-amputees, suggesting that increased knee loads leading to joint disorders may develop in response to prolonged prosthesis usage or the onset of joint pathology over time. In addition, the results showed that decreasing ESAR foot stiffness can increase prosthesis range of motion, mid-stance energy storage, and late-stance energy return. However, the prosthetic foot contributions to forward propulsion and swing initiation were limited due to muscle compensations needed to provide body support and forward propulsion in the absence of residual leg ankle muscles. A study was also performed that integrated design optimization with forward dynamics simulations of amputee walking to identify the optimal prosthetic foot stiffness that minimized metabolic cost and intact knee joint forces. The optimal stiffness profile stiffened the toe and mid-foot while making the ankle less stiff, which decreased the intact knee joint force during mid-stance while reducing the overall metabolic cost of walking. These studies have provided new insight into the relationships between prosthetic foot stiffness and amputee walking mechanics, which provides biomechanics-based rationale for prosthetic foot prescription that can lead to improved amputee mobility and overall quality of life. / text

Yes / Background Disruptions to the progress of the centre-of-pressure trajectory beneath prosthetic feet have been reported previously. These disruptions reflect how body weight is transferred over the prosthetic limb and are governed by the compliance of the prosthetic foot device and its ability to simulate ankle function. This study investigated whether using an articulating hydraulic ankle attachment attenuates centre-of-pressure trajectory fluctuations under the prosthetic foot compared to a fixed attachment. Methods Twenty active unilateral trans-tibial amputees completed walking trials at their freely-selected, comfortable walking speed using both their habitual foot with either a rigid or elastic articulating attachment and a foot with a hydraulic ankle attachment. Centre-of-pressure displacement and velocity fluctuations beneath the prosthetic foot, prosthetic shank angular velocity during stance, and walking speed were compared between foot conditions. Findings Use of the hydraulic device eliminated or reduced the magnitude of posteriorly directed centre-of-pressure displacements, reduced centre-of-pressure velocity variability across single-support, increased mean forward angular velocity of the shank during early stance, and increased freely chosen comfortable walking speed (P ≤ 0.002). Interpretation The attenuation of centre-of-pressure trajectory fluctuations when using the hydraulic device indicated bodyweight was transferred onto the prosthetic limb in a smoother, less faltering manner which allowed the centre of mass to translate more quickly over the foot.

While amputee gait has been studied in great detail, the influence of prosthetic foot sagittal and coronal plane stiffness on amputee walking biomechanics is not well understood. In order to investigate the effects of sagittal and coronal plane foot stiffness on amputee walking, a framework for manipulating the stiffness of a prosthetic foot needs to be developed. The sagittal and coronal plane stiffness of a low profile carbon fiber prosthetic foot was manipulated through coupling with selective-laser-sintered prosthetic ankles. The carbon fiber foot provided an underlying non-linear stiffness profile while the ankle modified the overall stiffness of the ankle-foot combination. A design of experiments was performed to determine the effect of four prosthetic ankle dimensions (keel thickness, keel width, space between the ankle top and bottom faces, and the location of the pyramid connection) on ankle-foot sagittal and coronal plane stiffness. Ankles were manufactured using selective laser sintering and statically tested to determine stiffness. Two of the dimensions, space between the ankle top and bottom faces and the location of the pyramid connection, were found to have the largest influence on both sagittal and coronal plane stiffness. A third dimension, keel thickness, influenced only coronal plane stiffness. A number of prosthetic ankle-foot combinations were created that encompassed a range of sagittal and coronal plane stiffness levels that were lower than that of the low profile carbon fiber foot alone. To further test the effectiveness of the framework to manipulate sagittal and coronal plane stiffness, two ankle-foot combinations, one stiffer than the other in the sagittal and coronal planes, were used in a case study analyzing amputee walking biomechanics. Differences in stiffness were large enough to cause noticeable changes in amputee kinematics and kinetics during turning and straight-line walking. Future work will expand the range of ankle-foot stiffness levels that can be created using this framework. The framework will then be used to create ankle-foot combinations to investigate the effect of sagittal and coronal plane stiffness on gait mechanics in a large sample of unilateral transtibial amputees. / text

Subject of this diploma thesis is a design of a prosthetic foot for an additive manufacturing. It is a dynamic foot made of plastic, designed for an 80 kg patient with a second level of a movement aktivity. From a few concepts is chosen one, which is then optimalized and printed with a MJF method. Functional sample is then undergoing static and cyclic tests according to ISO 10328.

Yes / Introduction: Clinicians typically use findings from cohort studies to objectively inform judgements regarding the potential (dis)advantages of prescribing a new prosthetic device. However, before finalising prescription a clinician will typically ask a patient to ‘try out’ a change of prosthetic device while the patient is at the clinic. Observed differences in gait when using the new device should be the result of the device’s mechanical function, but could also conceivably be due to patient related factors which can change from day-to-day and can thus make device comparisons unreliable. To determine whether a device’s mechanical function consistently has a more meaningful impact on gait than patient-related factors, the present study undertook quantitative gait analyses of a trans-tibial amputee walking using two different foot-ankle devices on two occasions over a year apart. If the observed differences present between devices, established using quantitative gait analysis, were in the same direction and of similar magnitude on each of the two occasions, this would indicate that device-related factors were more important than patient-related factors. Methods: One adult male with a unilateral trans-tibial amputation completed repeated walking trials using two different prosthetic foot devices on two separate occasions, 14 months apart. Walking speed and sagittal plane joint kinematics and kinetics for both limbs were assessed on each occasion. Clinically meaningful differences in these biomechanical outcome variables were defined as those with an effect size difference (d) between prosthetic conditions of at least 0.4 (i.e. ‘medium’ effect size). Results: Eight variables namely, walking speed, prosthetic ‘ankle’ peak plantar- and dorsi- flexion and peak positive power, and residual knee loading response flexion, peak stance-phase extension and flexion moments and peak negative power, displayed clinically meaningful differences (d > 0.4) between foot devices during the first session. All eight of these showed similar effect size differences during the second session despite the participant being heavier and older. Conclusions: Findings suggest that a prosthetic device’s mechanical function consistently has a more meaningful impact on gait than patient-related factors. These findings support the current clinical practice of making decisions regarding prosthetic prescription for an individual, based on a single session evaluation of their gait using two different devices. However, to confirm this conclusion, a case series using the same approach as the present study could be undertaken.

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).