Changes In Foot Position Research Articles

The Effect of Static Trial on Knee Adduction Moment During Walking.

Background and aim Sophisticated technologies in rehabilitation, such as three-dimensional gait analysis, allow for measuring kinematic and kinetic variables while performing activities. The first peak external knee adduction moment (EKAM) is considered an important outcome in individuals with knee osteoarthritis (OA) and has been shown to be affected by changes in foot position in static trials. The present study aimed to explore the variables in static trials that may lead to changes in the value of the EKAM while walking. Methods Twelve individuals participated in the current study and were asked to perform three static trials as follows: 20° toe-out, straight (0°), and 20° toe-in. The participants were asked to walk five trials (their own shoes and paces). The first peak EKAM was the main study outcome and was compared between conditions. Linear regression was used to investigate which variables in the static trials significantly predicted the magnitude of change in the EKAM while walking. Results The first peak EKAM significantly decreased by 8.2% while walking when changing the foot position in static trials from 20° toe-in to 20° toe-out. The magnitude of change in the EKAM was significantly (p<0.01) predicted by the magnitude of change in the knee joint frontal plane angle, shank transverse plane angle, ankle joint frontal plane angle, and hip joint frontal plane angle during static trials between 20° toe-in and 20° toe-out. The model was able to predict 94% of the variation in the EKAM due to changes in foot position during static trials. Conclusion Modifications in foot position during static trials led to a change in the first peak EKAM while walking. Researchers should focus on controlling the knee joint frontal plane angle, shank transverse plane angle, ankle joint frontal plane angle, and hip joint frontal plane angle during static trials when conducting longitudinal or crossover studies. Controlling these variables is necessary to reduce the likelihood of the EKAM being affected by static trials and to ensure that the EKAM changes in dynamic trials are not masked or increased by static trials.

Effect of 3 Weeks of Strict Head‑Down Tilt Bed Rest on Human Muscle Fuction and Architecture

The aim of this study was to first, experimentally measure in vivo changes in the length, fiber angle and thickness of the medial gastrocnemius muscle (MG) in young men in response to changes in foot position and joint moment during isometric plantar flexion and, in secondly, to compare the changes in the above characteristics of the muscular architecture that occur during the transition from a state of rest to a given isometric intensity during plantar flexion. The internal architecture of the MG was determined after 21-day of strict head‑down tilt bed rest (HDT). MG scanning was performed using ultrasound at rest at ankle joint angles of –15° (dorsiflexion), 0° (neutral), +15° and +30° (plantar flexion). Additional ultrasounds were performed during maximal voluntary contraction (MVC) and additionally at 80, 60, 40, and 20% of the MVC with the ankle in neutral position. In each position, longitudinal ultrasound images of the MG were obtained in a relaxed (passive) state with the determination of the length (Lf) and angles of fascicles (Θf) relative to the aponeurosis. After HDT, the thickness of the MG during graduated isometric force up to 80% of the MVC in the neutral position of the ankle joint remained constant. Various Lf and Θf and their changes after HDT can be a limiting factor in the generation of muscle contractile functions. The results of the study show that the change in muscle structure during contraction compared to rest, as measured by changes in muscle architecture, can be used to assess muscle mechanical output.

Plain Radiographs are Insufficient for Evaluation of First Metatarsal Pronation in Patients Undergoing Surgery for Hallux Valgus

Category: Midfoot/Forefoot; Bunion Introduction/Purpose: Previous studies using weight-bearing CT (WBCT) have suggested that up to 30% of patients with hallux valgus may have excessive pronation of the first metatarsal when defined as a metatarsal pronation angle (MPA) of greater than 16 degrees (Najefi et al.). The MPA is calculated on coronal slices of a CT or MRI, but axial imaging is not the norm in the assessment of these patients. It is however unclear how accurate radiographs are at determining pronation. This study aimed to assess the degree of pre-operative first metatarsal pronation in patients undergoing surgery for hallux valgus using radiographs and WBCT. Methods: This was a retrospective review of patients undergoing scarf osteotomy for hallux valgus correction. Patients were included if they had both plain radiographs and WBCT. Patients were excluded if they had any prior surgery to the foot in question. Pre-operative weightbearing plain radiographs of the foot were analyzed and the classification by Okuda et al. was used to determine if pronation was present using the shape of the lateral edge of first metatarsal head. Pre-operative WBCTs were reviewed and MPA calculated. Twenty-two feet were included. Results: In total 10 feet (45.5%) had an ‘angular’ first metatarsal head, 9 (40.9%) had an ‘intermediate’ head shape, and 3 (13.6%) had a ‘round’ head on plain radiographic assessment. The overall mean MPA was 16.25 degrees (range 2.1-30), and 12 (54.5%) feet had an MPA of greater than 16 degrees (excessively pronated). There was a strong correlation between increasing MPA and increasing roundness of the metatarsal head (Eta = 0.952). The mean MPA was 14.4 degrees in the angular head group, 17.0 degrees in the intermediate group, and 20.1 degrees in the round head group. In the intermediate and round groups 9 feet (75%) had greater pronation than the normal range. By contrast, only 3 (30%) of feet in the round head group had pronation greater than 16 degrees. Conclusion: In this surgical population of hallux valgus patients, the overall prevalence of excessive first metatarsal pronation was greater than in general cohorts of hallux valgus patients. Patients with intermediate and round shaped heads on plain radiographs tended to have greater first metatarsal pronation than those with angular shaped heads, although the correlation was not perfect. This suggests that plain radiographic assessment of metatarsal rotation may not be accurate as there may be discrepancies due to changes in foot position or angle of beam while acquiring the radiographs. Although further work is still required to determine whether there is clinical benefit from addressing the pronation, axial imaging (such as with WBCT) may be useful in the intermediate and round groups for accurate assessment of pronation and to determine if it is significant. This may be especially relevant in surgical candidates in whom osteotomies such as a scarf are being considered, where pronation cannot be addressed.

First trimester physiological development of the fetal foot position using three‐dimensional ultrasound in virtual reality

AimIn anatomic studies of the embryo, it has been established that during the development of the lower limb, several changes in foot position can be observed defined as a temporary ‘physiological clubfoot’. The aim of this study was to develop and test a measurement tool for objective documentation of the first trimester foot position in vivo and made an attempt to create a chart for first trimester foot position.MethodsWe developed a virtual orthopedic protractor for measuring foot positioning using three‐dimensional virtual reality visualization. Three‐dimensional ultrasound volumes of 112 pregnancies of women examined during the first trimester were studied in a BARCO I‐Space. The frontal angle (plantar flexion) and the lateral angle (adduction) between the leg and foot were measured from 8 until 13 weeks gestational age.ResultsWe observed that the frontal angle steadily decreases, whereas the lateral angle first increases, resulting in transient physiological clubfeet position at 10‐ to 11‐week gestation, followed by a decrease to a normal foot position.ConclusionA transient clubfoot position is present during the normal development of the lower limbs, and it has been measured in vivo for the first time. This study emphasizes that a diagnosis of congenital clubfoot should not be made in the first trimester of pregnancy.

Changes in tibialis anterior architecture affect the amplitude of surface electromyograms

BackgroundVariations in the amplitude of surface electromyograms (EMGs) are typically considered to advance inferences on the timing and degree of muscle activation in different circumstances. Surface EMGs are however affected by factors other than the muscle neural drive. In this study, we use electrical stimulation to investigate whether architectural changes in tibialis anterior (TA), a key muscle for balance and gait, affect the amplitude of surface EMGs.MethodsCurrent pulses (500 μs; 2 pps) were applied to the fibular nerve of ten participants, with the ankle at neutral, full dorsi and full plantar flexion positions. Ultrasound images were collected to quantify changes in TA architecture with changes in foot position. The peak-to-peak amplitude of differential M waves, detected with a grid of surface electrodes (16 × 4 electrodes; 10 mm inter-electrode distance), was considered to assess the effect of changes in TA architecture on the surface recordings.ResultsOn average, both TA pennation angle and width increased by respectively 7 deg. and 9 mm when the foot moved from plantar to dorsiflexion (P < 0.02). M-wave amplitudes changed significantly with ankle position. M waves elicited in dorsiflexion and neutral positions were ~25% greater than those obtained during plantar flexion, regardless of where they were detected in the grid (P < 0.001). This figure increased to ~50% when considering bipolar M waves.ConclusionsFindings reported here indicate the changes in EMG amplitude observed during dynamic contractions, especially when changes in TA architecture are expected (e.g., during gait), may not be exclusively conceived as variations in TA activation.

A kicking simulator to investigate the foot-ball interaction during a rugby place kick.

Foot-ball interaction is an important aspect in rugby place kicking but has received very little attention in literature. This preliminary study presents an adjustable mechanical kicking simulator used to investigate different foot positions and orientations during the foot-ball interaction on resultant ball motion. It was found that changes in foot position and orientation during ball contact can have a large influence on ball motion. It is believed that with further research an optimal place-kicking technique can be found to maximize energy transfer to the ball while still maintaining accuracy.

Scientific Assessment of Over-the-Counter Foot Orthoses to Determine Their Effects on Pain, Balance, and Foot Deformities

A scientific study was conducted to evaluate the effects of non-custom-molded (over-the-counter) foot orthoses. Several parameters were examined, including foot, knee, hip, and back pain; balance; and reduction in flexible deformities, such as hammer toes and hallux valgus. Wherever possible, objective measurements were used, including measurements of shifts in center of pressure to assess balance and changes in bone position examined on radiographs. Forty-one individuals were analyzed using one of two types of prefabricated, non-custom insoles. Insoles were fit by an assistant trained to follow the fitting recommendations of the manufacturer under the direct supervision of a podiatric physician. Use of these arch supports resulted in a significant reduction in some types of foot pain associated with hallux valgus (P = .04) and pain in the arch area (P = .004), knee (P = .002), and back (P = .007) by week 4. We also measured changes in foot position documented by radiography, although some changes may be attributed to parallax associated with measurement techniques. Improvement in balance was not observed to be significant when the orthoses were worn. Using both subjective and objective measures, we found that these over-the-counter foot orthoses were effective in bringing about changes in foot shape and concomitant relief of certain specific painful conditions. This study indicates that there is a scientific basis for attempting to relieve pain with orthoses.

Differences in 3D kinematics between volleyball and beach volleyball spike movements

The purpose of this study was to identify differences between volleyball and beach volleyball spike jump movements performed on an indoor surface and sand surface respectively. Eight elite male volleyball players performed spike jump movements on both surfaces. An eight-camera motion capturing system (250 Hz) was used to generate 3D kinematic data. Seven groups of variables representing the kinematics of the centre of mass, the countermovement, the approach phase, and the angular amplitudes and maximal velocities of the lower and upper limbs were examined using Hotelling's . Significant differences were observed in the movement of the centre of mass (P < 0.05), the countermovement, the kinematics of the approach phase, and the angular amplitudes of the lower limbs. However, no significant differences were observed either in the maximal angular velocities of the lower and upper limbs, or in the amplitudes of the upper limb motion. In conclusion, the participants showed significant adaptation to changed movement conditions. As a result of the compliance of the sand surface, the participants slowed down their movements, especially during the phase of transition from knee flexion to extension and during the extension phase. Furthermore, the participants demonstrated changes in foot position to reach the greatest height possible.

Effect of foot rotation on knee kinetics and hamstring activation in older adults with and without signs of knee osteoarthritis

Background To determine the effects of changing the natural foot progression angle during gait (internal and external foot rotation) on the knee’s adduction moment, lateral–medial shear force, and the ratio of medial–lateral hamstring muscle activation in those with signs of knee osteoarthritis and a matched healthy control group. Methods Twelve subjects with signs of knee osteoarthritis and 12 matched healthy control subjects were evaluated. A 3D gait analysis system calculated forces and moments at the knee while the subjects walked in three conditions: (1) normal foot position, (2) external foot rotation, (3) internal foot rotation. Medial and lateral hamstring EMG data was also collected simultaneously and used to calculate the medial–lateral hamstring activation ratio during the stance phase of the gait cycle. Repeated measures ANOVAs were used to compare foot rotation conditions within each group; while between group comparisons were performed in the normal rotation condition only using t-tests. Findings Those with knee osteoarthritis (OA) had an increased late stance knee adduction moment and a decreased medial–lateral hamstring activation ratio as compared to the healthy control group. Also, external foot rotation decreased the late stance knee adduction moment, lateral–medial shear force, and hamstring activation ratio. However, internal foot rotation did not increase these measures. Interpretation Changes in foot position during gait have the ability to alter both the external loading of the knee joint and hamstring muscle activation patterns during gait. This may have implication in helping to unload the knee’s articular cartilage.

Representation of passive hindlimb postures in cat spinocerebellar activity.

1. We report here about the modulation of dorsal spinocerebellar tract (DSCT) activity by limb posture. In principle, DSCT activity could represent limb position in one of several ways. According to a classical notion of DSCT function, DSCT activity might be expected to correlate with changes in individual joint angles. However, given the evidence for extensive polysynaptic convergence onto DSCT units, it is reasonable to propose that DSCT activity represents more global variables such as the orientation of limb segments or the length and orientation of the whole limb. 2. In six anesthetized cats we recorded the activity of 96 antidromically identified DSCT neurons while a robot arm passively positioned the left hindfoot in 20 positions distributed in the sagittal plane, holding each position for 8 s. For each position we measured the joint angles, limb segment angles, and the length and orientation of the limb axis (defined as the line connecting the hip joint to the hindpaw). We used regression statistics to quantify 1) possible relationships among geometric variables of the hindlimb and 2) relationships between DSCT firing rate and limb variables. 3. First, we found a statistically significant relationship among the joint angles that could be described by a covariance plane accounting for approximately 70 percent of the total variance. Thus the 3 degrees of freedom represented by the joint angles in the sagittal plane are effectively reduced to only 2 by the coupling between joints. This finding resembles that described for the behaving cat during stance. However, the correlation between the hip and ankle angles in the passively displaced hindlimb was just the opposite of that observed during active stance. Moreover, we observed that the length and the orientation of the limb axis is determined simply by a linear combination of the three joint angles. 4. Most of the DSCT neurons (82 of 96) were significantly modulated by changes in foot position (1-way analysis of variance, P < 0.001). For those cells, we explored systematically how their activity was related to limb geometric variables. We found mostly linear relationships between individual joint or limb segments angles and DSCT firing rates. However, although these relationships were statistically significant, the random variance was often quite high. Moreover, approximately 70% of the cells were modulated by more than one joint or limb segment angle, suggesting that a model incorporating global geometric variables might explain a larger fraction of the variance in the neural data. 5. Consequently we tested how well DSCT activity was modulated by the length and the orientation of the limb axis with the use of a linear regression model with length and orientation (or the equivalent linear combination of joint angles) as predictors. We found that this model explained a larger fraction of the variability in the firing pattern of nearly every modulated cell than did any of the single joint models tested. 6. We also attempted to account for the effect of the mechanical joint covariance on this result by accounting for correlated independent variables in the analysis. We used a regression model incorporating all three joint or limb segment angles and performed a backward elimination of insignificant or redundant variables. The result was that 67% of the neurons were independently modulated by at least two joint angles, indicating that the modulation did not necessarily reflect the biomechanical constraint of joint angle covariation, but rather a central convergence of sensory information from more than a single joint. 7. From these results we conclude that the firing rates of a majority of DSCT neurons encode the position of the hindfoot relative to the hip joint.(ABSTRACT TRUNCATED)