Are wearable insoles a validated tool for quantifying transfemoral amputee gait asymmetry?

Abstract

Background: Amputee gait is known to be asymmetrical, especially during loading of the lower limb. Monitoring asymmetry could be useful in quantifying patient performance during rehabilitation. Wearable insoles can provide normal ground reaction force asymmetry in real-life conditions. Objectives: To characterize the validity of Loadsol® insoles versus force plates in quantifying normal ground reaction force and gait asymmetry. To determine the influence walking speed has on loading asymmetry in transfemoral amputees. Study design: This is a prospective study. Methods: Six transfemoral amputees, wearing Loadsol® insoles, walked at three self-selected speeds on force plates. Validity was assessed by comparing normal ground reaction force data from the insoles and force plates. The Absolute Symmetry Index was used to calculate gait loading asymmetry at each speed. Results: Normalized root mean square errors for the normal ground reaction forces were 6.6% (standard deviation = 2.3%) and 8.9% (standard deviation = 3.8%); correlation coefficients were 0.91 and 0.95 for the prosthetic and intact limb, respectively. The mean error for Absolute Symmetry Index parameters ranged from −2.67% to 4.35%. Loading asymmetry increased with walking speed. Conclusion: This study quantified the validity of Loadsol® insoles in assessing loading asymmetry during gait in transfemoral amputees. The calibration protocol could be improved to better integrate it into a clinical setting. However, our results support the relevance of using such insoles during the clinical follow-up of transfemoral amputees. Clinical relevance This is the first study to validate Loadsol® insoles versus force plates and report on loading asymmetry during gait at three different speeds in transfemoral amputees. Loadsol® insoles, which provide visual and audio feedback, are clinically easy to use and could have beneficial application in the amputee’s rehabilitation and follow-up.

Gait event detection using inertial measurement units in people with transfemoral amputation: a comparative study

“…Reference GEs were obtained using pressure insoles (Loadsol, Novel, Germany, 100 samples s −1 ). These insoles have been reported to be reliable and to accurately estimate both vertical ground reaction force and stance phase duration in TF [8] and were, thus, considered a valid gold standard.…”

“…Reference IC and FC events were identified using a 20 N threshold on the insoles' ground reaction force signals [8,18].Regarding the IMUs' signals, five GE detection algorithms were selected based on a literature review. The first three algorithms were the only one retrieved that were specifically designed for people with lower-limb amputation.…”

“…In recent years, wearable sensors, such as pressure insoles or inertial measurement units (IMUs), have been proposed as a portable and low-cost alternative to force platforms, instrumented mats, or treadmills for the detection of GEs. While some specific pressure insoles have been validated against force platforms [7,8], their use is limited to the obtention of GEs and vertical ground reaction forces. On the other hand, IMUs, which include accelerometers and gyroscopes, can provide kinematic information in addition to GE detection.…”

“…Although there have been some attempts in performing comparative studies in the literature [16,24,27,28], none focused on people with transfemoral amputation (TF). In addition, as most algorithms rely on the extraction of specific features from IMU signals, some may not be relevant for the population of TF because of deviations in their gait pattern, such as hip hiking, vaulting, delayed knee flexion, and temporal and spatial asymmetries [2,8].…”

“…Furthermore, the robustness to different walking speeds was also investigated. Data from pressure insoles validated against force platforms in people with transfemoral amputation [8] were used for reference values assessment.…”