Effects of prosthetic foot forefoot flexibility on oxygen cost and subjective preference rankings of unilateral transtibial prosthesis users

Abstract

Abstract-The investigators conducted a double-blind randomized crossover study to determine the effects of prosthetic foot forefoot flexibility on oxygen cost and subjective preference rankings of 13 unilateral transtibial prosthesis users. Five experimental feet were fabricated for use in the study: F1, F2, F3, F4, and F5. F1 was most flexible, F5 was least flexible, and F3 was designed to conform to a biomimetic ankle-foot rollover shape. The experimental feet were modeled after the Shape&Roll prosthetic foot (originally produced by Northwestern University, Chicago, Illinois; now in public domain) but had different numbers of saw cuts within the forefoot members, allowing more or less flexibility during walking. Participants walked at the same comfortable, freely selected speed on the treadmill for 7 min with each foot while energy expenditure was measured. No significant difference was found in oxygen cost (mL O 2 /kg/m) between the different feet (p = 0.17), and the order of use was also not significant (p = 0.94). However, the preference ranking was significantly affected by the flexibility of the feet (p = 0.002), with the most flexible foot (F1) ranking significantly poorer than feet F3 (p = 0.003) and F4 (p = 0.004). Users may prefer prosthetic feet that match the flexibility of an intact ankle-foot system, even though we did not detect an energetic benefit at freely selected speeds.

Stance phase mechanical characterization of transtibial prostheses distal to the socket: A review

“…Following selection for relevance and including those resulting from the secondary search, we identified 36 articles that satisfied the criteria [2][3][5][6][7][13][14][15][16][17][18][19][20][21][22]. In addition, five relevant review articles were identified [1,[8][9][11][12].…”

“…As a follow-up to the this study, two additional studies by Klodd et al also used the "Shape&Roll" prosthetic foot in order to study the effects of forefoot roll-over shape on gait kinematics, kinetics, and oxygen cost [21][22]. Changes to forefoot roll-over shape were achieved in a foot of the same length by increasing the number of cutouts made in the dorsal aspect of the forefoot.…”

“…Changes to forefoot roll-over shape were achieved in a foot of the same length by increasing the number of cutouts made in the dorsal aspect of the forefoot. Although the aim was to create five foot conditions with different forefoot stiffnesses, the cutouts were designed such that each foot condition would achieve a specific in vivo rollover shape radius, and hence, primarily geometries, not stiffness properties, were being altered [22]. Furthermore, results indicated that the in vivo roll-over shape remained invariant across conditions apart from a decrease in the in vivo roll-over shape arc length (i.e., forefoot moment arm) with increasing number of cutouts [21].…”

“…Because the primary information distinguishing the prostheses is their trade names and/or classification (e.g., conventional or energy storage and return [ESAR] in the case of prosthetic feet [1]), this approach can only indicate their relative performance but cannot provide information on why a particular prosthesis performs better than the next. A smaller number of studies have characterized prostheses in terms of their AIPPs; however, with notable exceptions [7,[13][14][15][16][17][18][19][20][21][22], very few authors have combined both types of study in an attempt to understand the correlations between AIPPs and their effects on amputee gait (comfort, biomechanics, and physiological performance). Furthermore, these correlations can also be investigated through simulations of amputee gait that incorporate AIPP-based prosthesis models.…”

Effect of prosthetic design on center of pressure excursion in partial foot prostheses

“…As suggested in another study [30], the cuts might have been too close together to function as intended. Future work should investigate a different approach to modulation of forefoot stiffness, such as deepening or widening the cuts.…”