A team of researchers designed a prosthetic ankle with the goal of reducing fall risk by dorsiflexing the ankle joint during swing to provide an increase in the minimum clearance between the foot and ground. Unlike previous approaches to providing swing dorsiflexion, such as powered ankles or hydraulic systems with dissipative yielding in-stance, the ankle has a spring-loaded linkage that adopts a neutral angle during stance. The researchers say this allows energy storage and return (ESR) but adopts a dorsiflexed angle during swing.
The ankle design was intended to obtain swing-phase dorsiflexion as well as stance-phase ESR without incorporating other biomechanical features such as slope adaptation to achieve the biomechanical goals without the use of electromechanical or hydraulic componentry, according to the study.
To validate the device, a participant who uses a unilateral transtibial prosthesis completed level-ground walking trials under three conditions: the ankle in an operational configuration, the ankle in a locked configuration (unable to dorsiflex), and the subject’s daily-use ESR prosthesis.
When the ankle was operational, minimum foot clearance increased by 13mm relative to the locked configuration and 15mm relative to the participant’s daily-use prosthesis. Stance-phase energy return was not significantly impacted in the operational configuration. The increase in minimum foot clearance may be sufficient to decrease the rate of falls experienced by prosthesis users in the real world, the study’s authors concluded.
The open-access study, “A passive dorsiflexing ankle prosthesis to increase minimum foot clearance during swing,” was published online by Cambridge University Press.
