Foot kinematics in patients with two patterns of pathological plantar hyperkeratosis

Background: The Root paradigm of foot function continues to underpin the majority of clinical foot biomechanics practice and foot orthotic therapy. There are great number of assumptions in this popular paradigm, most of which have not been thoroughly tested. One component supposes that patterns of plantar pressure and associated hyperkeratosis lesions should be associated with distinct rearfoot, mid foot, first metatarsal and hallux kinematic patterns. Our aim was to investigate the extent to which this was true. Methods: Twenty-seven subjects with planter pathological hyperkeratosis were recruited into one of two groups. Group 1 displayed pathological plantar hyperkeratosis only under metatarsal heads 2, 3 and 4 (n = 14). Group 2 displayed pathological plantar hyperkeratosis only under the 1st and 5th metatarsal heads (n = 13). Foot kinematics were measured using reflective markers on the leg, heel, midfoot, first metatarsal and hallux. Results: The kinematic data failed to identify distinct differences between these two groups of subjects, however there were several subtle (generally <3°) differences in kinematic data between these groups. Group 1 displayed a less everted heel, a less abducted heel and a more plantarflexed heel compared to group 2, which is contrary to the Root paradigm. Conclusions: There was some evidence of small differences between planter pathological hyperkeratosis groups. Nevertheless, there was too much similarity between the kinematic data displayed in each group to classify them as distinct foot types as the current clinical paradigm proposes

Neuromechanical response of the upper body to unexpected perturbations during gait initiation in young and older adults

Background: Control of upper body motion deteriorates with ageing leading to impaired ability to preserve balance during gait, but little is known on the contribution of the upper body to preserve balance in response to unexpected perturbations during locomotor transitions, such as gait initiation. Aim: To investigate differences between young and older adults in the ability to modify the trunk kinematics and muscle activity following unexpected waist lateral perturbations during gait initiation. Methods: Ten young (25 ± 2 years) and ten older adults (73 ± 5 years) initiated locomotion from stance while a lateral pull was randomly applied to the pelvis. Two force plates were used to define the feet centre-of-pressure displacement. Angular displacement of the trunk in the frontal plane was obtained through motion analysis. Surface electromyography of cervical and thoracic erector spinae muscles was recorded bilaterally. Results: A lower trunk lateral bending towards the stance leg side in the preparatory phase of gait initiation was observed in older participants following perturbation. Right thoracic muscle activity was increased in response to the perturbation during the initial phase of gait initiation in young (+ 68%) but not in older participants (+ 7%). Conclusions: The age-related reduction in trunk movement could indicate a more rigid behaviour of the upper body employed by older compared to young individuals in response to unexpected perturbations preceding the initiation of stepping. Older adults’ delayed activation of thoracic muscles could suggest impaired reactive mechanisms that may potentially lead to a fall in the early stages of the gait initiation

Validity and reliability of a kinematic protocol for determining foot contact events

Timing of foot contact events provides important information for gait studies. The aim of the study is to validate the use of kinematic data, collected at 50 Hz to define foot contact events during gait initiation. Simultaneous kinetic and kinematic data recordings of four discrete foot contact events were made for normal adults. Raters were asked to estimate the timing of the events from kinematic data curves and these timings were compared with those derived from the kinetic data. For the four events, between 88 and 98% of all ratings were accurate to within 0.03 s. Inter-rater reliability was extremely high, reflecting the precision of the definitions used

Determination of Gait events using an externally mounted shank accelerometer

Biomechanical analysis requires the determination of specific foot contact events. This is typically achieved using force platform information, however when force platforms are unavailable, alternative methods are necessary. A method was developed for the determination of gait events using an accelerometer mounted to the distal tibia, measuring axial accelerations. The aim of the investigation was to determine the efficacy of this method. Sixteen participants ran at 4.0m.s-1 ±5 %. Synchronized axial tibial accelerations and vertical ground reaction forces were sampled at 1000 Hz as participants struck a force platform with their dominant foot. Events determined using the accelerometer were compared to the corresponding events determined using the force platform. Mean errors for heel strike events of 1.68 and 5.46 ms for average and absolute errors respectively. For toe-off events average and absolute errors of -3.59 and 5.00 ms were calculated. Mean and absolute errors of 5.18 and 11.47 ms were also found for the duration of the stance phase. Strong correlations r=0.96 were also observed between duration of stance obtained using the two different methods. The error values compare favourably to other alternative methods of predicting gait events. This suggests that shank mounted accelerometers can be used to accurately and reliably detect gait events