Prosthetic weight acceptance mechanics in transtibial amputees wearing the Single Axis, Seattle Lite, and Flex Foot

Abstract

Loading response challenges the limb with the dual demands of accepting rapidly moving body weight to both absorb the shock of floor contact and create a stable limb over which the body can advance. Delay in achieving foot flat contact with the floor causes a prolonged period of heel only support and results in an unstable base of support for those persons with transtibial amputations. The purpose of this study was to identify mechanical causes of instability during weight acceptance with three different prosthetic foot designs, Single Axis, Seattle Lightfoot, and Flex Foot. Ten male individuals with transtibial amputations were tested on three separate occasions wearing each prosthetic foot. A comparison group of ten individuals without transtibial amputations was also examined. Mean free walking speed was significantly slower for those with transtibial amputations regardless of the prosthetic foot worn (p < 0:05). Contralateral toe off times were significantly later for each prosthetic foot (p < 0:01). The timing of peak knee flexion was found to be significantly later than normal for each prosthetic foot (p < 0:01). To minimize the impact of initial floor contact, persons with an intact limb used rapid plantar flexion, followed by a slower lowering of the foot to the floor. Dorsiflexion then stimulated knee flexion and foot flat. Two altered functions were found for all three prosthetic feet, reduced knee flexion and prolonged heel only support. Diminished knee flexion reflected delayed dorsiflexion and tibial advancement as a result of the cushioned heel. Lateness in reaching foot flat was also found. To improve the walking abilities of those persons with transtibial amputations, prosthetic foot designs need to incorporate mechanisms which promote early foot flat while preserving limb stability.

Gait characteristics of persons with bilateral transtibial amputations

“…The persons with bilateral transtibial amputations in this study walked with less peak-to-peak stance-phase knee flexion than the nondisabled individuals walking at similar speeds. Other studies have reported decreased stance-phase knee flexion in persons with unilateral transtibial amputations [12,23]. The subjects with amputations may have attempted to reduce stance-phase knee flexion to minimize relative motion between the residual limb and the prosthetic socket and to avoid high, uncomfortable pressures by maintaining the GRF vector orientation nearly coincident with the longitudinal axis of their residual limb.…”

“…The inferior walking performance of persons with amputations is often attributed to the current state of prosthetic technology [11][12]14,[16][17]]. This conclusion is based on gait studies of persons with unilateral transtibial amputations.…”

“…The sagittal-plane ankle motion on the prosthetic side of persons with transtibial amputations is generally smaller than that of nondisabled persons [11]. Peak stance-phase knee flexion on the prosthetic side is typically reduced compared with nondisabled persons [6,12]. During prosthetic swing phase, persons with unilateral transtibial amputations sometimes exhibit hip hiking [13], a compensatory motion in which the pelvis is lifted on the prosthetic side to increase foot clearance.…”

Porous composite prosthetic pylon for integration with skin and bone

“…In the gait of a person with an amputation, the prosthetic joint amplitude is typically lower than in the gait of a nondisabled person [18][19]. Therefore, 15° of dorsiflexion is a reasonable target [20]. We did not consider the moment from the horizontal component of the ground reaction force because it would only decrease the value of M(α) as calculated in Equation 1, but we used the conservative approach to estimate the needed stress for …”

Design and Qualitative Testing of a Prosthetic Foot With Rotational Ankle and Metatarsal Joints to Mimic Physiological Roll-Over Shape

“…While it is known that persons with lower limb amputations have slower self-selected walking speeds [16][17][18], increased nonprosthetic side leg loading [19], and decreased gait symmetry [19][20][21][22][23] compared to persons with no physical impairments, typical, unimpaired gait data were used in calculating the roll-over shape of the prototype in this study. Typical loading is often assumed in measuring the roll-over shape of prosthetic feet through mechanical testing [5,9,24].…”