Microprocessor knees with ‘standing support’ and articulating, hydraulic ankles improve balance control and inter-limb loading during quiet standing

Abstract

Introduction Trans-femoral amputees are at risk of musculoskeletal problems that are in part caused by loading asymmetry during activities, such as prolonged standing, particularly on uneven or sloped ground. Methods Four prosthetic conditions were tested; microprocessor knee ‘standing support’ mode activated (ON) and deactivated (OFF), combined with a rigidly attached foot (RA) and with an articulating, hydraulic ankle-foot (HA). Five trans-femoral amputees and five able-bodied controls were measured using a motion capture system and a force plate while standing, facing down a 5° slope. Ground reaction force distributions and centre-of-pressure root-mean-square (COP RMS) were calculated as outcome measures. Results Compensatory kinematic adjustments were observed for RA conditions but not for HA conditions. HA-OFF reduced ground reaction force degree-of-asymmetry for all five amputees, compared to RA-OFF. RA-ON reduced ground reaction force degree-of-asymmetry for four amputees, compared to RA-OFF. In terms of balance, the HA conditions reduced the mean inter-limb COP RMS by 24–25% compared to equivalent RA conditions, while ON conditions reduced it by 9–11%, compared to equivalent OFF conditions. Conclusions It is important to consider both prosthetic knee and ankle technologies when prescribing devices to trans-femoral amputees. The combination of hydraulic ankle and knee standing support technologies produced outcomes closest to normal biomechanics.

The Influence of Hydraulic Ankles and Microprocessor-Control on the Biomechanics of Trans-Tibial Amputees During Quiet Standing on a 5° Slope

“…This is defined as the sum of the moments acting at the ankle, knee and hip, where extension moments make up the positive contribution to support and flexion moments provide a negative one. 23 This study expands on the previous work 19 to focus on TTAs and, in particular, how differences in prosthetic foot and ankle technology can influence the way in which they stand on non-level ground. Two hypotheses were tested.…”

“…Hydraulic ankles, which produce a viscoelastic response when loaded, allow a degree of damped movement proximal to the foot springs, 'self-aligning' with the ground and helping to maintain the body's COM position relative to the lower limb joints. 19,22 This action minimises undesirable biased forces and moments acting on the limb, thus it may also reduce the compensations needed to enable effective standing on uneven surfaces. 19 Previous work has used the ground reaction force (GRF) to determine the inter-limb load distribution during transfemoral amputee (TFA) standing tests.…”

“…19,22 This action minimises undesirable biased forces and moments acting on the limb, thus it may also reduce the compensations needed to enable effective standing on uneven surfaces. 19 Previous work has used the ground reaction force (GRF) to determine the inter-limb load distribution during transfemoral amputee (TFA) standing tests. 19 This approach, however, does not consider the loading at individual joints, which could provide greater insight into which joints are most at risk of OA development.…”

Development of a theoretical model for upright postural control in lower limb prosthesis users

“…Utilizing the new model, in conjunction with properly-controlled study designs, we can now begin to explore the individual contributions of the intact and prosthetic side on postural control in this subject group. This could be applied to the assessment of prosthetic components effects of on upright posture, particularly those devices whose functionality is aimed at stabilizing the lower limb to improve balance 35 . This would shed light not only on the overall performance but also the relative function of each limb and how the individual is responding to the alterations in device set-up.…”

OASIS 1: Retrospective analysis of four different microprocessor knee types

“…14,15 Other frequently utilized MPKs, such as the Pli e (Freedom Innovations, Irvine, California, United States) and the Orion (Blatchford Group, Basingstoke, Hampshire, United Kingdom) received limited consideration in recent literature. 9,11,17 Analyses comparing different MPKs are infrequent, and when they have occurred, they are generally short-term observations on small study cohorts that carry a risk of actual or perceived bias due to direct manufacturer funding and publication. 9,10,12…”