Reliability of the step phase detection using inertial measurement units: pilot study.

The use of inertial sensors for the gait event detection during a long-distance walking, for example, on different surfaces and with different walking patterns, is important to evaluate the human locomotion. Previous studies demonstrated that gyroscopes on the shank or foot are more reliable than accelerometers and magnetometers for the event detection in case of normal walking. However, these studies did not link the events with the temporal parameters used in the clinical practice; furthermore, they did not clearly verify the optimal position for the sensors depending on walking patterns and surface conditions. The event detection quality of the sensors is compared with video, used as ground truth, according to the parameters proposed by the Gait and Clinical Movement Analysis Society. Additionally, the performance of the sensor on the foot is compared with the one on the shank. The comparison is performed considering both normal walking and deviations to the walking pattern, on different ground surfaces and with or without constraints on movements. The preliminary results show that the proposed methodology allows reliable detection of gait events, even in case of abnormal footfall and in slipping surface conditions, and that the optimal location to place the sensors is the shank.

Effects of laterally wedged insoles on knee and subtalar joint moments.

OBJECTIVE: To assess the biomechanic effects of wearing a lateral wedge on the knee joint varus moment during gait in elders with and without knee osteoarthritis (OA). DESIGN: Crossover design whereby subjects walked under 2 different insole conditions: a 0 degrees control wedge and a 6 degrees lateral wedge. SETTING: A gait laboratory with 3-dimensional motion analysis and force platform equipment. PARTICIPANTS: Thirteen healthy subjects and 13 knee patients with OA. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Frontal plane angles and moments at the knee and subtalar joints, ground reaction forces, and center of pressure. Moments were derived by using a 3-dimensional inverse dynamics model of the lower extremity. RESULTS: The 6 degrees lateral wedge significantly reduced knee joint varus moment and increased subtalar joint valgus moment in both groups when compared with no wedge. All patients had a greater knee joint varus moment with a similar subtalar joint valgus moment compared with the people without OA. There were diverse, sometimes reversed effects with the insole among the patients. CONCLUSIONS: The 6 degrees lateral wedge did not consistently reduce the knee joint varus moment in patients with knee OA. The biomechanic indications and limitations of laterally wedged insoles should be confirmed by a larger study.

Gait analysis of people walking on tactile ground surface indicators.

Tactile ground surface indicators installed on sidewalks help visually impaired people walk safely. The visually impaired distinguish the indicators by stepping into its convexities and following them. However, these indicators sometimes cause the nonvisually impaired to stumble. This study examines the effects of these indicators by comparing the kinematic and kinetic variables of walking on paths with and without indicators. The results suggest that walking on the indicators causes extra movements of the lower extremities such as increased minimum toe heights during the midswing phase, increased peak hip flex moments, and increased peak hip heights. This study also suggests that a functional leg length discrepancy while walking on the indicators is one of the reasons for the extra movements of the lower extremities. Therefore, we designed a new recessed tactile surface to offset the differences of surface depth while walking on the path containing indicators, and found that the newly designed recessed tactile surface was effective in reducing the extra movements while walking on the path in which indicators were installed. These indicators may help both the visually impaired and elderly people with normal vision to walk safely.

Changes of joint moments in the gait of normal subjects wearing laterally wedged insoles.

OBJECTIVE: The purpose of this study was to assess the kinematic and kinetic effects of wearing a laterally wedged insole on the knee joint moment during gait, specifically in the frontal plane, in normal healthy adults. DESIGN: Motion analyses were conducted with (1) a three-dimensional motion analysis system and (2) ground reaction force analysis using force platforms when subjects walked under three different insole conditions: no wedge, a low wedge with a 3-degree lateral angle, and a high wedge with a 6-degree lateral angle. RESULTS: The high-wedge insole significantly reduced the knee joint varus moment during gait compared with the gait with the no-wedge insole. The actual segment angles at the subtalar and knee joints did not show any changes due to insole conditions. In contrast, the subtalar joint valgus moment increased for the high-wedge insole. This finding was correlated with a greater moment arm of the subtalar joint valgus moment with the high-wedge insole. CONCLUSIONS: These results indicate that, under dynamic conditions, the subjects wearing laterally wedged insoles had both changes of moments at the subtalar and knee joints via the more laterally shifted location of the center of pressure.