Impact of a prosthetic foot on lower limb amputees gait

Gait is a pattern of locomotion defined as "manner of walking", it involves the use of both limbs to alternatively provide support and propulsion. Insights on the neuromuscular state of a subject are inferred from gait analysis as non-invasive technique of diagnosis and follow up for medical treatment, and, beyond clinical perspectives, to assess quality of life. Particularly, prosthesis are commonly evaluated by their closeness to its classic paradigm. This work inspects the existence of a statistically significative difference in spatio-temporal parameters of lower limb amputees gait when compared to non-amputee walkers. Amputee sample is constituted by eighteen Trans Tibial and three Trans Femoral patients fitted with the novel passive foot prosthesis of the company "Axiles Bionics" and compared to a sample of fourteen intact-limbed individuals. Subjects are tested on treadmill with two-minute trials for three different speed, data is collected by inertial measurements units (IMUs). Divergences from physiological gait might occur in the form of limb variation of parameters for subject of the same population, generating asymmetries, and differences in singular limb comparison of samples with different pathological/physiological conditions. Even if both samples ideally had equal asymmetries, differences might still occur when limbs of different populations are compared. Assessment is carried on as it follows: best set of asymmetry indexes is chosen in order to select the most informative combination and reduce redundancy, consequently, evaluation of differences is performed. Employed discrete indexes are: Limp Index (LI), Degree of Asymmetry (DoA), Symmetry Angle (SA), Gait Asymmetry (GA) and Temporal Asymmetry index (TAI). The first four provide a parameter-specific asymmetry assessment, the last one accounts for a global evaluation. Correlation is stronger between the first three, with no significative differences in standard deviations when changing variable, index and speed. Prosthetic device has the same dispersion in asymmetry measurements, for each index and speed, in amputees and non-amputees. This works reveals that robust choice for asymmetry analysis are: SA, provides the actual measurement and indicates limb prevalence, and TAI for its globality. Outcome of the second section shows amputees to have significantly different impairments, increasing with speed, despite not sensed by TAI index. Stance and single support are prevalent for sound limb, while swing and trail double support are longer for prosthetic foot. Amputees display lower speed and cadence but higher stride and step durations. Gait difference evaluation highlights some features of the device. Amputees rely more on their intact limb, which might be a sign of non complete adjustment, however, passive nature of the prosthesis causes the increase of its step and rapid load transmission to it, faster than that on sound limb, interpretable as confidence with the prosthesis and enthusiasm in testing a new device. These considerations are enforced by the qualitative assessment resulting from surveys collected from amputees after gait trials: the prosthesis was defined as stable and capable of restoring a natural feeling, generally better than their current one.