A Clinical Comparison of Variable-Damping and Mechanically Passive Prosthetic Knee Devices

TLDR

Variable‑damping knee prostheses promise improvements over mechanically passive designs for transfemoral amputees, yet evidence for benefits at self‑selected walking speeds remains limited. This study compares two variable‑damping knees—the hydraulic‑based Otto Bock C‑leg and the magnetorheological‑based Ossur Rheo—to a mechanically passive hydraulic Mauch SNS in eight unilateral amputees walking at self‑selected speeds on an indoor track. Metabolic, kinetic, kinematic, and electromyographic data were collected from the participants while walking at self‑selected speeds across a 10‑m laboratory walkway and an indoor track. Variable‑damping knees reduced metabolic rate by 5% versus the passive Mauch and 3% versus the C‑leg, and improved gait smoothness, hip work, peak hip flexion moment, and peak hip power, indicating overall advantages over passive designs and suggesting magnetorheological systems may outperform hydraulic ones.

Abstract

Although variable-damping knee prostheses offer some improvements over mechanically passive prostheses to transfemoral amputees, there is insufficient evidence that such prostheses provide advantages at self-selected walking speeds. In this investigation, we address this question by comparing two variable-damping knees, the hydraulic-based Otto Bock C-leg and the magnetorheological-based Ossur Rheo, with the mechanically passive, hydraulic-based Mauch SNS.For each prosthesis, metabolic data were collected on eight unilateral amputees walking at self-selected speeds across an indoor track. Furthermore, kinetic, kinematic, and electromyographic data were collected while walking at self-selected speeds across a 10-m walkway in a laboratory.When using the Rheo, metabolic rate decreases by 5% compared with the Mauch and by 3% compared with the C-leg. Furthermore, for the C-leg and Rheo knee devices, we observe biomechanical advantages over the mechanically passive Mauch. These advantages include an enhanced smoothness of gait, a decrease in hip work production, a lower peak hip flexion moment at terminal stance, and a reduction in peak hip power generation at toe-off.The results of this study indicate that variable-damping knee prostheses offer advantages over mechanically passive designs for unilateral transfemoral amputees walking at self-selected ambulatory speeds, and the results further suggest that a magnetorheological-based system may have advantages over hydraulic-based designs.