Three-dimensional quantitative analysis of healthy foot shape: a proof of concept study.

BACKGROUND: Foot morphology has received increasing attention from both biomechanics researches and footwear manufacturers. Usually, the morphology of the foot is quantified by 2D footprints. However, footprint quantification ignores the foot's vertical dimension and hence, does not allow accurate quantification of complex 3D foot shape. METHODS: The shape variation of healthy 3D feet in a population of 31 adult women and 31 adult men who live in Belgium was studied using geometric morphometric methods. The effect of different factors such as sex, age, shoe size, frequency of sport activity, Body Mass Index (BMI), foot asymmetry, and foot loading on foot shape was investigated. Correlation between these factors and foot shape was examined using multivariate linear regression. RESULTS: The complex nature of a foot's 3D shape leads to high variability in healthy populations. After normalizing for scale, the major axes of variation in foot morphology are (in order of decreasing variance): arch height, combined ball width and inter-toe distance, global foot width, hallux bone orientation (valgus-varus), foot type (e.g. Egyptian, Greek), and midfoot width. These first six modes of variation capture 92.59% of the total shape variation. Higher BMI results in increased ankle width, Achilles tendon width, heel width and a thicker forefoot along the dorsoplantar axis. Age was found to be associated with heel width, Achilles tendon width, toe height and hallux orientation. A bigger shoe size was found to be associated with a narrow Achilles tendon, a hallux varus, a narrow heel, heel expansion along the posterior direction, and a lower arch compared to smaller shoe size. Sex was found to be associated with differences in ankle width, Achilles tendon width, and heel width. Frequency of sport activity was associated with Achilles tendon width and toe height. CONCLUSION: A detailed analysis of the 3D foot shape, allowed by geometric morphometrics, provides insights in foot variations in three dimensions that can not be obtained from 2D footprints. These insights could be applied in various scientific disciplines, including orthotics and shoe design.

Human-robot interaction: kinematics and muscle activity inside a powered compliant knee exoskeleton.

Until today it is not entirely clear how humans interact with automated gait rehabilitation devices and how we can, based on that interaction, maximize the effectiveness of these exoskeletons. The goal of this study was to gain knowledge on the human-robot interaction, in terms of kinematics and muscle activity, between a healthy human motor system and a powered knee exoskeleton (i.e., KNEXO). Therefore, temporal and spatial gait parameters, human joint kinematics, exoskeleton kinetics and muscle activity during four different walking trials in 10 healthy male subjects were studied. Healthy subjects can walk with KNEXO in patient-in-charge mode with some slight constraints in kinematics and muscle activity primarily due to inertia of the device. Yet, during robot-in-charge walking the muscular constraints are reversed by adding positive power to the leg swing, compensating in part this inertia. Next to that, KNEXO accurately records and replays the right knee kinematics meaning that subject-specific trajectories can be implemented as a target trajectory during assisted walking. No significant differences in the human response to the interaction with KNEXO in low and high compliant assistance could be pointed out. This is in contradiction with our hypothesis that muscle activity would decrease with increasing assistance. It seems that the differences between the parameter settings of low and high compliant control might not be sufficient to observe clear effects in healthy subjects. Moreover, we should take into account that KNEXO is a unilateral, 1 degree-of-freedom device.

The added value of an actuated ankle-foot orthosis to restore normal gait function in patients with spinal cord injury: a systematic review.

OBJECTIVE: To provide an overview of robot-assisted rehabilitation devices developed for actuation of the ankle-foot complex and their ability to influence the attributes of normal gait in patients with spinal cord injury. METHODS: A search was conducted in MEDLINE, Web of Knowledge, National Academic Research and Collaborations Information System, and Physiotherapy Evidence Data-base (1985-2011), using, "ankle", "foot", "robotics", "orthotics" and "spinal cord injury" as most relevant keywords. Article inclusion was performed in 3 stages; at the level of: (i) title, (ii) abstract and (iii) full text. RESULTS: The actuated ankle-foot orthoses currently available are characterized by several combinations of an actuator and a control mechanism. Both the actuator and the control strategy substantially influence human-machine interaction and therefore the potential of the device to assist in modifying locomotor function and potentially modify the underlying motor control mechanisms. CONCLUSION: Due to small sample sizes, limited studies in patients with spinal cord injury, and limitations in study design, it is difficult to draw firm conclusions on the effect of different types of actuated ankle-foot orthoses. Based on the limited data available, pneumatic artificial muscles in combination with proportional myoelectric control are suggested to have the potential to meet most of the preconditions to restore the attributes of normal gait and therefore facilitate neuroplasticity.

Effectiveness of robot-assisted gait training in persons with spinal cord injury: a systematic review.

OBJECTIVE: To assess the quality of current evidence as to the effectiveness of robot-assisted gait training in spinal cord injured patients, focusing on walking ability and performance. METHODS: A search was conducted in MEDLINE, Web of Knowledge, Cochrane Library, Physiotherapy Evidence Database (PEDro) and Digital Academic Repositories (DAREnet) (1990-2009). Key words included "spinal cord injury", "(robot-assisted) gait rehabilitation" and "driven gait orthosis". Articles were included when complete and incomplete adult spinal cord injured patients participated in robot-assisted gait training intervention studies. The methodological quality was rated independently by 2 researchers using "van Tulder criteria list" and "evaluation of quality of an intervention study". Descriptive analyses were performed using the Population Intervention Comparison Outcome (PICO) method. RESULTS: Two randomized controlled trials (mean quality score: 11.5/19) and 4 pre-experimental trials (mean quality score: 24.25 (standard deviation; SD 0.28)/48) involving 43 patients with incomplete, acute or chronic lesions between C3 and L1 were analysed. Five studies used the Lokomat and one used the LokoHelp. Although some improvements were reported related to body functions and activities, there is insufficient evidence to draw firm conclusions, due to small samples sizes, methodological flaws and heterogeneity of training procedures. CONCLUSION: There is currently no evidence that robot-assisted gait training improves walking function more than other locomotor training strategies. Well-designed randomized controlled trials are needed.