Search Results
Viscoelastic inserts are commonly used as artificial shock absorbers to prevent neuropathic foot ulcerations by decreasing pressure on the sole of the foot. Unfortunately, there is little scientific information available to guide physicians in the selection of appropriate insole materials. Therefore, a novel methodology was developed to form a rational platform for biomechanical characterizations of insole material durability, which consisted of in vivo gait analysis and in vitro bioengineering measurements. Results show significant differences in the compressive stiffness of the tested insoles and the rate of change over time in both compressive stiffness and peak pressures measured. Good correlations were found between pressure-time integral and Young's modulus (r2 = 0.93), and total energy applied and Young's modulus (r2 = 0.87).
Reduction in first metatarsophalangeal joint maximum degree of dorsiflexion with dorsiflexion of the first ray has been proposed to be the predominant cause of hallux abducto valgus and hallux rigidus. We sought to determine whether orthoses made from a cast with the first ray plantarflexed and a 4-mm medial skive could increase the maximum degree of dorsiflexion in patients with functional hallux limitus in stance and gait. Forty-eight feet of 27 subjects were casted for orthoses with the first ray plantarflexed and in the customary neutral rearfoot position with locked midtarsal joint. First metatarsophalangeal joint maximum dorsiflexion was measured with and without orthoses in stance, and subhallux pressure was measured with and without orthoses at heel-off. Changes in mean maximum dorsiflexion in stance and in mean maximum subhallux pressure in gait with orthoses were significant. We investigated the relationship between this increase in dorsiflexion and gender, shoe size, resting calcaneal stance position, and change in resting calcaneal stance position with the use of orthoses. These correlations were not statistically significant. The biomechanical implication of increasing limited first metatarsophalangeal joint dorsiflexion with orthoses is discussed and related to the clinical treatment of deformities, including hallux valgus and hallux rigidus. The use of orthoses to decrease subhallux pressure is also discussed. (J Am Podiatr Med Assoc 96(6): 474–481, 2006)
Background:
We sought to investigate the different configurations of Kirschner wires used in distal femur Salter-Harris (SH) type 2 epiphyseal fracture for stabilization after reduction under axial, rotational, and bending forces and to define the biomechanical effects on the epiphyseal plate and the fracture line and decide which was more advantageous.
Methods:
The SH type 2 fracture was modeled using design software for four different configurations: cross, cross-parallel, parallel medial, and parallel lateral with two Kirschner wires, and computer-aided numerical analyses of the different configurations after reduction were performed using the finite element method. For each configuration, the mesh process, loading condition (axial, bending, and rotational), boundary conditions, and material models were applied in finite element software, and growth cartilage and von Mises stress values occurring around the Kirschner wire groove were calculated.
Results:
In growth cartilage, the stresses were highest in the parallel lateral configuration and lowest in the cross configuration. In Kirschner wires, the stresses were highest in the cross configuration and lowest in the cross-parallel and parallel lateral configurations. In the groove between the growth cartilage and the Kirschner wire interface, the stresses were highest in the parallel lateral configuration and lowest in the cross configuration.
Conclusions:
The results showed that the cross configuration is advantageous in fixation. In addition, in the SH type 2 epiphyseal fracture, we believe that the fixation shape should not be applied in the lateral configuration.
Abstract
Background: Flat feet change lower extremity alignment, and it may change the load distribution on Achilles tendon during exercise. The purpose of the present study was to investigate the immediate effect of cumulative transverse strain via resistive ankle plantarflexion exercise on the Achilles tendon in individuals with flat feet.
Methods: Fourteen individuals with flat feet and 14 age-matched individuals with normal foot posture were enrolled in the present study. Achilles tendon thickness was measured by an ultrasonography device with a linear probe at 3 points: 1 cm (AT-1), 2 cm (AT-2), and 3 cm (AT-3) proximal to the superior aspect of the calcaneus. Ultrasonography measurements were performed before and after participants completed 90 repetitions of double-leg calf raise exercises which included moving the foot from full ankle dorsiflexion to full ankle plantarflexion.
Results: Achilles tendon thickness at all points measured was thinner in the flat feet group at both pre- and post-exercise conditions compared with that of the control group (p<0.05). Achilles tendon thickness at AT-1, AT-2, and AT-3 decreased after the exercise in both groups (p<0.001). The differences in Achilles tendon thickness at all points measured between pre- and post-exercise conditions were lower in individuals with flat feet than those of the control group (p<0.05).
Conclusion: There was a significant decrease in Achilles tendon thickness after exercise in both groups; however, the tendon thickness markedly diminished in individuals with normal foot posture. The results are thought to result from changes in tendon structure and in load distribution on the Achilles tendon.
Background
Wearing high-heeled shoes and carrying asymmetrical loads are common in ladies. However, knowledge of the effects of wearing high-heeled shoes on balance and lower-extremity biomechanics in experienced and novice high-heeled shoe wearers is lacking. The study aims to examine the effects of high-heeled shoes and asymmetrical load carrying on joint kinematics and kinetics of the lower extremity during walking as well as balance in experienced and novice high-heeled shoe wearers.
Methods
Fifteen experienced and 15 novice high-heeled shoes wearers participated in this study. Using a motion analysis system, kinematic and kinetic data were collected while participants walked at their preferred speed in six conditions created from two types of shoes (9-cm high-heeled shoes and flat-heeled shoes) and three weights of symmetrical load (0%, 5%, and 10% of body weight). Stride time and length, step length, double support time, peak joint angles, and joint moments in a sagittal plane were analyzed. Single-leg and tandem-leg stance tests were performed in each condition.
Results
Compared with experienced high-heeled shoe wearers, novice high-heeled shoe wearers had longer double support time and shorter stride length during 10% of body weight asymmetrical load walking; walked with greater knee flexion angle, smaller knee range of motion, and smaller ankle dorsiflexor moment; and scored lower in the single-leg and tandem-leg stance tests.
Conclusions
Novice high-heeled shoe wearers need to alter their lower-limb joint angles and moments to adjust to high-heeled shoes to achieve balance during gait while carrying an asymmetrical load.
Biomechanical foot function as expressed by the duration of successive ground contact phases and by dynamic variables, such as the peak pressure on different parts of the foot, their respective loading rate, and duration, is compared for two walking and running conditions: overground on a 20-m walkway and on a treadmill. Statistical analysis revealed foot pressure characteristics as measured with a Electrodynogram during walking and running to alter significantly when using a treadmill. The differences were more pronounced for walking than for running. During walking, loading of the forefoot tends to last longer (longer propulsion phase) on a treadmill. Loading rate is decreased for the whole foot during either walking or running. Maximum heel pressure is diminished for walking but increased during running on a treadmill. Moderate variations of treadmill velocity were shown to have no significant influence on the measurements.
This article presents a critical examination of biomechanics studies in the literature that could shed light on or contribute to the development of methods of managing intra-articular calcaneal fractures. An appreciation and understanding of such studies is predicated on a sound knowledge of a number of germane topics: the anatomy of the normal calcaneus, the pathomechanics of the calcaneus, fracture-classification schemes, and fracture-management methods. The first part of this review presents overviews of these topics. The biomechanics studies are then reviewed in detail. The article concludes with a description of research areas that might close the gaps identified in these studies.
Background: Research on foot orthoses has shown that their effect on the kinematics of the rearfoot is variable, with no consistent patterns of changes being demonstrated. It has also been hypothesized that the mechanical effect of foot orthoses could be subject specific. The purpose of our study was to determine if maximally pronated feet have a different response to frontal plane wedging of foot orthoses than do nonmaximally pronated feet during static stance.
Methods: One hundred six feet of 53 healthy asymptomatic subjects were divided into two groups (maximally pronated and nonmaximally pronated) on the basis of their subtalar joint rotational position during relaxed bipedal stance. Functional foot orthoses were constructed for each subject and the relaxed calcaneal stance position was measured while standing on five separate frontal plane orthosis wedging conditions, 10° valgus, 5° valgus, no wedging, 5° varus, and 10° varus, to assess changes in calcaneal position.
Results: Relative to the no-wedging condition, there were statistically significant differences (P < .05) in calcaneal position between the maximally pronated and the nonmaximally pronated feet with the 10° valgus and the 10° varus wedging conditions. No significant differences in calcaneal position were found with the 5° varus and the 5° valgus wedging conditions.
Conclusions: Our study shows that the response to foot orthoses is variable between individuals. Maximally pronated subjects do not exhibit the same response to frontal plane wedging of foot orthoses as do nonmaximally pronated with 10° wedging. Intrinsic biomechanical factors such as subtalar joint position may influence the response to foot orthoses. (J Am Podiatr Med Assoc 99(1): 13–19, 2009)
Abstract
Background: This study aims to evaluate and compare stiffness and the load to failure values of our novel medial malleolus compression plate (MP) and 3,5mm 1/3 tubular plate (TP) in the treatment of vertical shear fractures of medial malleolar fractures.
Methods: Fourteen identical synthetic third generation composite polyurethane bone models of right distal tibia were randomly separated into two groups. Fracture models were created with a custom-made osteotomy guide to provide the same fracture characteristics in every sample (AO OTA type 44A2). Fractures were reduced and novel medial malleolus compression plate was applied to bone models in MP group and tubular plate was applied to TP group. All samples were evaluated biomechanically, force/displacement and the load to failure values were recorded.
Results: The force required to create displacement in MP group was twice of that of the TP group. There was a significant difference between two groups in all amounts of displacement (p = .006, p = .005, p = .007 and .015 for 0.5, 1.0, 1.5, and 2.0 mm, respectively).
Conclusions: In the treatment of vertical shear fractures of the medial malleolus, the strength of fixation with the novel medial malleolar compression plate is biomechanically higher than the one-third semi-tubular plate.
The authors investigated the function of the tarsus and the skeletal segments of the foot in terms of the biomechanical significance of the individual links of the foot-ankle-leg complex. A performance model based on pressure-washed trabecular systems and the interface of the different segments making up the articular foot skeleton is presented and discussed. The biomechanical influence of these segments on each other and on their appendicular companion bones is assessed, and an explanation of their function is provided.