Assessment of Safety and Performances of a 3D Printed Prosthetic Foot: A Pilot Study

Adverse events may be: falling, stumbling, lower back pain as consequence of the prosthesis foot use, stump pain as consequence of the prosthesis foot use, breakage of the prosthesis foot

The IMUs record joints kinematics while subjects perform a series of motor tasks, i.e. walk of flat surfaces at a self-selected speed and ascend/descend stairs and ramps. In particular, the following variables are measured: range of motion of ankle joint (prosthetic ankle), knee joint, and hip joint of the impaired lower limb. The measured angles are normalized on a gait cycle (0% = heel strike, 100% = toe off). The outocome variable is computed as mean difference between the normalized measured angles and the normalized reference value taken from the literature.

The optoelectronic system records joints kinematics while subjects walk of a flat surfaces at a self-selected speed. In particular, the following variables are measured: range of motion of ankle joint (prosthetic ankle), knee joint, and hip joint of the impaired lower limb. The measured angles are normalized on a gait cycle (0% = heel strike, 100% = toe off). The outocome variable is computed as mean difference between the normalized measured angles and the normalized reference value taken from the literature.

Hill Assessment Index (HAI) is a 12-points ordinal scale used to evaluate ramp ascending quality; the higher the score the better the gait quality while ascending ramps (0 = cannot do/refuse to do, 11 = even step, without assistive device) .

Stair Ascending Index (SAI) is 14-points ordinal scale used to quantify stair ascending qualty; the higher the score the better the gait quality while ascending stairs (0 = cannot do/refuse to do, 13 = Without rail or assistive device, step-over-step pattern)

The subject is asked to stand still on a force plate for 30 seconds. The sway path of the Centre of Pressure (COP) is recorded. The higher the valure the sway path, the lower the equilibrium in orthostatism. This outcome measure is performed with the eyes open and closed

The subject is asked to sit on a chair with both the feets (sound foot and prosthesis foot) on different force plates. At the "Start" signal, the subject stands up, stands still for 5 seconds and sits down. The weigth distribution on the lower limbs is recorded during the entire task. The symmetry index is computed as the ratio between: the difference between the load peak of the ground reaction force (GRF) measured in the sound side and the load peak of the ground reaction force (GRF) measured in the impaired side ON the sum between the load peak of the ground reaction force (GRF) measured in the sound side and the load peak of the ground reaction force (GRF) measured in the impaired side.

Asymmetry index = [(peak GRF sound - peak GRF impaired) / (peak GRF sound + peak GRF impaired)]*100%

AMP is a 21-item objectve measure in which static and dynamic sitting and standing activities, as well as transfer and gait skills of progressing difficulty are performed. Score range is 0-47. Higher scores indicate better mobility. Based on the final score, 4 groups are defined (K1 = 15-26, K2 = 27-36, K3 = 37-42, K4 = 43-47).

The subject starts from a sitting position. At the "Start" signal, the subject stands up from the chair, walks in a closed 10-meters L-shaped path, and sits down on the same chair. The time necessary to complete the path is measured with a stopwatch. The lower the time to complete the path, the higher the functional mobility.

Usability is measured with an ad hoc custom-made 6-items questionnaire. Each item ranges 1 to 5. To compute the final score, each item is summed up (total range: 6-30). The higher the score, the better the usability.