Symmetry in External Work (SEW)

Abstract

Unilateral transtibial amputees (TTAs) show subtle gait variations while using different prosthetic feet. These variations have not been detected consistently with previous experimental measures. We introduce a novel measure called Symmetry in External Work (SEW) for quantifying kinetic gait differences between prosthetic feet. External work is the result of changes in kinetic and potential energy of body center of mass (CoM). SEW is computed by integrating vertical ground reaction forces obtained using F-scan in-sole sensors. Since various prosthetic feet have different designs, we hypothesized that SEW will vary with the type of foot used. This hypothesis was tested with a single unilateral TTA using four prosthetic feet (Proprio, Triasþ, Seattle Lite and SACH). The Proprio (mean symmetry 94.5% + 1.1%) and the Triasþ (92.1% + 2.5%) feet exhibited higher symmetry between the intact and prosthetic limbs, as compared to the Seattle (67.8% + 19.3%) and SACH (35.7% + 11.1%) feet. There was also a good agreement in vertical CoM excursion between the intact foot and prosthetic feet with heel-toe foot plate designs. Results indicate that SEW measure may be a viable method to detect kinetic differences between prosthetic feet and could have clinical applications because of relatively low cost instrumentation and minimal subject intervention.

Active dorsiflexing prostheses may reduce trip-related fall risk in people with transtibial amputation

“…In general, the evidence supporting the use of microprocessor-controlled prosthetic feet for improving balance, function, and/or mobility of people with amputation is limited and has only recently begun to appear in the literature (e.g., references [25][26][27][28][29][30]). At present, there are few English-written studies of the ProprioFoot, and those that exist have focused on socket pressures [31], hip and knee kinematics and kinetics [32][33], gait economy [34][35], and related aspects of gait [36][37] but not on MTC. Our study is the first to quantify MTC at different speeds and inclines and to report a reduced likelihood of tripping by people with TTAs.…”

Application of self-report and performance-based outcome measures to determine functional differences between four categories of prosthetic feet

“…Interestingly, the non-PVD group demonstrated an improvement in their AMPPRO scores after initial training and with the Proprio foot, which would suggest that the Proprio foot improved the function in a select group. The Proprio foot has been described in the literature as a quasipassive prosthetic ankle that can actively change the ankle angle in swing phase of level walking and ascending and descending ramps and stairs in order to improve the knee kinematics of the amputated limb during late stance and throughout the swing phase of gait [41][42][43]. Agrawal et al found that the Proprio foot promoted higher symmetry in level walking between the intact and prosthetic limb than other prosthetic feet [43].…”

“…The Proprio foot has been described in the literature as a quasipassive prosthetic ankle that can actively change the ankle angle in swing phase of level walking and ascending and descending ramps and stairs in order to improve the knee kinematics of the amputated limb during late stance and throughout the swing phase of gait [41][42][43]. Agrawal et al found that the Proprio foot promoted higher symmetry in level walking between the intact and prosthetic limb than other prosthetic feet [43]. Other benefits of the Proprio foot on functional activities such as ascending and descending stairs and ramps have been described in the literature [27][28].…”

Comparison between microprocessor-controlled ankle/foot and conventional prosthetic feet during stair negotiation in people with unilateral transtibial amputation

“…Symmetry in External Work (SEW) is a biomechanical measure that can detect interlimb kinetic asymmetry during stair ascent and descent [11]. In this measure, external work done by the intact and prosthetic limbs is calculated by integrating ground reaction forces (GRFs) and center of mass (COM) displacement over a step [12]. This measure has the potential to be made clinically friendly because it can assess amputation gait kinetics with minimal resources and in the everyday environment.…”

“…This measure has the potential to be made clinically friendly because it can assess amputation gait kinetics with minimal resources and in the everyday environment. During level walking, the SEW measure has been shown to successfully differentiate gait asymmetry between prosthetic feet having diverse designs and functional properties [12]. The purpose of this study was to compare the effect of functional prosthetic ankle dorsiflexion on SEW values between a microprocessor-controlled foot and three conventional prosthetic feet in two groups with unilateral TTA (MFCL K-Level-2 and K-Level-3) as they ascended and descended a staircase with 11 steps.…”