Using a three-dimensional model of the Ankle–Foot Orthosis/leg to explore the effects of combinations of axis misalignments

Background and Aim: Misaligning the mechanical axes of Ankle–Foot Orthoses with the ankle axis may lead to tissue damage, reduced gait efficiency, and mechanical wear on the orthosis. Previous models developed to describe the consequences of joint misalignments have only been applied to the sagittal plane. In this study, a previously developed three-dimensional model of the Ankle–Foot Orthosis/leg system was used to determine the effects of misalignments in the frontal and transverse planes and how they interact with misalignments in the sagittal plane. Technique: The motion of two corresponding points on the leg and Ankle–Foot Orthosis was calculated for different binary combinations of translational and rotational misalignments of the mechanical axis, and the resulting displacements between those points recorded. Discussion: Misaligning the mechanical joint axis of the Ankle–Foot Orthosis in the transverse plane led to much greater displacements than other misalignments. Results from the model suggest the importance of prioritizing transverse plane alignment by appropriately accounting for tibial rotation. Clinical relevance: Misalignments in the transverse plane had a dominating effect on relative motion between the Ankle–Foot Orthosis and leg emphasizing the importance of including the third dimension in the model and prioritizing accuracy of alignment in the transverse plane.

Download Full-text

A three-dimensional model to assess the effect of ankle joint axis misalignments in ankle–foot orthoses

Prosthetics and Orthotics International ◽

10.1177/0309364614543551 ◽

2014 ◽

Vol 40 (2) ◽

pp. 240-246 ◽

Cited By ~ 1

Author(s):

Stefania Fatone ◽

William Brett Johnson ◽

Kerice Tucker

Keyword(s):

Ankle Joint ◽

Three Dimensional ◽

Foot Orthoses ◽

Two Dimensional ◽

Dimensional Model ◽

Three Dimensional Model ◽

Ankle Foot Orthosis ◽

Joint Axis ◽

Ankle Foot Orthoses ◽

Foot Orthosis

Background: Misalignment of an articulated ankle–foot orthosis joint axis with the anatomic joint axis may lead to discomfort, alterations in gait, and tissue damage. Theoretical, two-dimensional models describe the consequences of misalignments, but cannot capture the three-dimensional behavior of ankle–foot orthosis use. Objectives: The purpose of this project was to develop a model to describe the effects of ankle–foot orthosis ankle joint misalignment in three dimensions. Study design: Computational simulation. Methods: Three-dimensional scans of a leg and ankle–foot orthosis were incorporated into a link segment model where the ankle–foot orthosis joint axis could be misaligned with the anatomic ankle joint axis. The leg/ankle–foot orthosis interface was modeled as a network of nodes connected by springs to estimate interface pressure. Motion between the leg and ankle–foot orthosis was calculated as the ankle joint moved through a gait cycle. Results: While the three-dimensional model corroborated predictions of the previously published two-dimensional model that misalignments in the anterior -posterior direction would result in greater relative motion compared to misalignments in the proximal -distal direction, it provided greater insight showing that misalignments have asymmetrical effects. Conclusions: The three-dimensional model has been incorporated into a freely available computer program to assist others in understanding the consequences of joint misalignments. Clinical relevance Models and simulations can be used to gain insight into functioning of systems of interest. We have developed a three-dimensional model to assess the effect of ankle joint axis misalignments in ankle–foot orthoses. The model has been incorporated into a freely available computer program to assist understanding of trainees and others interested in orthotics.

Download Full-text

A Model to Predict the Effect of Ankle Joint Misalignment on Calf Band Movement in Ankle-Foot Orthoses

Prosthetics and Orthotics International ◽

10.1080/03093640600983873 ◽

2007 ◽

Vol 31 (1) ◽

pp. 76-87 ◽

Cited By ~ 10

Author(s):

Stefania Fatone ◽

Andrew H. Hansen

Keyword(s):

Ankle Joint ◽

Walking Speed ◽

Sagittal Plane ◽

Plantar Flexion ◽

Dimensional Model ◽

Ankle Foot Orthosis ◽

Ankle Joints ◽

Ankle Foot Orthoses ◽

Foot Orthosis ◽

Anterior Posterior

Accurate alignment of anatomical and mechanical joint axes is one of the major biomechanical principles pertaining to articulated orthoses, yet knowledge of the potential effects of axis misalignment is limited. The purpose of this project was to model the effects of systematic linear (proximal-distal and anterior-posterior) misalignments of single axis mechanical ankle joints in an ankle-foot orthosis (AFO) in order to determine the degree and direction of calf band travel that would occur over a functional range of motion. Sagittal plane misalignments of the ankle joint centres of an AFO were simulated using a simple two-dimensional model for both a range of ankle angles and a typical able-bodied ankle kinematic curve for self-selected normal walking speed. The model assumed that no movement occurred between the foot and the foot-plate of the AFO. The model predicted that for anterior (positive horizontal) misalignments, dorsiflexion movements would cause the calf band to travel proximally (i.e., up the leg) and plantar flexion movements would cause the calf band to travel distally (i.e., down the leg). The opposite was predicted for posterior (negative horizontal) misalignments. Proximal (positive vertical) misalignments would cause only distal movements of the calf band while distal (negative vertical) misalignments would cause only proximal movements of the calf band. Anterior-posterior misalignments were found to have a much larger effect on the amount of calf band travel than proximal-distal misalignments.

Download Full-text

Muscling in on the third dimension

eLife ◽

10.7554/elife.06430 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 2

Author(s):

Mohsen Afshar Bakooshli ◽

Penney M Gilbert

Keyword(s):

Skeletal Muscle ◽

Muscle Tissue ◽

Human Skeletal Muscle ◽

Three Dimensional ◽

Dimensional Model ◽

Three Dimensional Model ◽

Muscle Disorders ◽

The Third ◽

Third Dimension ◽

Skeletal Muscle Disorders

The development of a functional three-dimensional model of human skeletal muscle tissue could accelerate progress towards new and personalized treatments for skeletal muscle disorders.

Download Full-text

The effect of custom carbon ankle-foot orthosis alignment on roll-over shape and center of pressure velocity

Prosthetics and Orthotics International ◽

10.1177/0309364620971407 ◽

2020 ◽

pp. 030936462097140

Author(s):

Elizabeth Russell Esposito ◽

Mitchell D Ruble ◽

Andrea J Ikeda ◽

Jason M Wilken

Keyword(s):

Lower Limb ◽

Sagittal Plane ◽

Center Of Pressure ◽

Heel Strike ◽

Control Group ◽

Foot Orthoses ◽

Ankle Foot Orthosis ◽

Ankle Foot Orthoses ◽

Foot Orthosis ◽

Center Of Pressure Velocity

Background: Maintaining an optimal rolling of the foot over the ground is thought to increase the stability and efficiency of pathologic gait. Ankle-foot orthoses are often prescribed to improve gait mechanics in individuals with lower extremity injuries; however, their design may compromise how the foot rolls over the ground. Objectives: The aim of this study was to investigate the effects of the sagittal plane ankle-foot orthosis alignment on roll-over shape and center of pressure velocity in individuals with lower limb reconstructions. Study design: Randomized cross-over study with a control group comparison. Methods: In total, 12 individuals with lower limb reconstruction who used a custom carbon ankle-foot orthosis and 12 uninjured controls underwent gait analysis. Ankle-foot orthosis users were tested in their clinically-provided ankle-foot orthosis alignment, with an alignment that was 3° more plantarflexed, and with an alignment that was 3° more dorsiflexed. Components of roll-over shape and center of pressure velocity were calculated from heel strike on the ankle-foot orthosis limb to contralateral heel strike. Results: Roll-over shape radius was not affected by 3° changes to alignment and was not significantly different from controls. Aligning the ankle-foot orthosis in more dorsiflexion than clinically provided resulted in a smaller peak center of pressure velocity that occurred later in stance. Conclusion: Individuals using custom carbon ankle-foot orthoses can accommodate 3° alterations in the dorsiflexion or plantarflexion alignment.

Download Full-text

Use and tolerability of a side pole static ankle foot orthosis in children with neurological disorders

Prosthetics and Orthotics International ◽

10.1177/0309364616640946 ◽

2016 ◽

Vol 41 (2) ◽

pp. 134-140 ◽

Cited By ~ 1

Author(s):

Céline Delvert ◽

Pascal Rippert ◽

Françoise Margirier ◽

Jean-Pierre Vadot ◽

Carole Bérard ◽

...

Keyword(s):

Neurological Disorders ◽

Frontal Plane ◽

Neurological Impairment ◽

Transverse Plane ◽

Foot Deformities ◽

Ankle Foot Orthosis ◽

Neurologic Disorders ◽

Ankle Foot Orthoses ◽

Neurological Pathology ◽

Foot Orthosis

Background: Transverse-plane foot deformities are a frequently encountered issue in children with neurological disorders. They are the source of many symptoms, such as pain and walking difficulties, making their prevention very important. Objectives: We aim to describe the use and tolerability of a side pole static ankle foot orthosis used to prevent transverse-plane foot deformities in children with neurologic disorders. Study design: Monocentric, retrospective, observational study. Methods: Medical data were collected from 103 children with transverse-plane foot deformities in one or both feet caused by a neurological impairment. All children were braced between 2001 and 2010. Results: Unilateral orthosis was prescribed for 32 children and bilateral orthosis for 71. Transverse-plane foot deformities were varus in 66% of the cases and an equinus was associated in 59.2% of the cases. Mean age for the first prescription was 8.6 years. For the 23 patients present at the 4-year visit, 84.8% still wore the orthosis daily, and 64.7% wore the orthosis more than 6 h per day. The rate of permanent discontinuation of wearing the orthosis was 14.7%. Conclusion: The side pole static ankle foot orthosis is well tolerated with very few side effects, which promotes regular wearing and observance. Clinical relevance Side pole static ankle foot orthoses are well tolerated and can be safely used for children with foot abnormalities in the frontal plane that have a neurological pathology origin.

Download Full-text

Three-Dimensional Diffusion of Carbon Monoxide in an Alveolar Capillary

Heat Transfer: Volume 1 ◽

10.1115/ht2005-72400 ◽

2005 ◽

Author(s):

Ali A. Merrikh ◽

Jose´ L. Lage

Keyword(s):

Gas Exchange ◽

Three Dimensional ◽

Gas Diffusion ◽

Numerical Results ◽

Gas Transfer ◽

Transfer Model ◽

Two Dimensional ◽

Dimensional Model ◽

Three Dimensional Model ◽

Third Dimension

Theoretical capillary gas exchange models available in the literature are limited to either two-dimensional or axisymmetric configurations. The present study investigates shortcomings of a two-dimensional capillary CO-gas transfer model by comparing it to a more realistic three-dimensional configuration. Numerical results from both models, compared to measurements obtained experimentally via the rebreathing technique, demonstrate that CO-diffusion model results are strongly affected when a third dimension is included. The effect of including a third dimension is to increase the gas exchange from the alveolar region into the RBCs, due to a larger gas diffusion surface within the capillary, leading to a significant increase in the resulting CO diffusing capacity. The results also show a better agreement between the experimental results and the numerical results obtained with the three-dimensional model than with the two-dimensional model. Finally, the strong sensitivity of the results vis-a`-vis the domain lengths (keeping the capillary volume constant) highlight the importance of considering the three-dimensional capillary morphology very carefully.

Download Full-text

Analysis of body-device interface forces in the sagittal plane for patients wearing ankle-foot orthoses

Prosthetics and Orthotics International ◽

10.3109/03093649909071615 ◽

1999 ◽

Vol 23 (1) ◽

pp. 75-81 ◽

Cited By ~ 11

Author(s):

B. McHugh

Keyword(s):

Stance Phase ◽

Muscle Power ◽

Sagittal Plane ◽

Swing Phase ◽

The Body ◽

Loss Of Function ◽

Ankle Foot Orthosis ◽

Ankle Foot Orthoses ◽

Foot Orthosis ◽

Interface Forces

An ankle-foot orthosis (AFO) is employed principally to treat musculoskeletal disorders of the ankle and/or subtalar joints although, occasionally, it may be prescribed to provide stance phase control of the knee. In order to function satisfactorily, an AFO must apply appropriate forces to the lower leg in a manner which does not cause local tissue damage or discomfort. Equally the leg will apply forces to the AFO which it must be capable of withstanding without breakage or loss of function. Thus it is useful to know where the body-device interface forces act during walking and to be able to estimate their magnitudes. This is not well understood and has not been satisfactorily documented. This paper explains the force actions between the AFO and the leg, in the sagittal plane, where there is absence of muscle power. Furthermore, it explores the possibility of estimating the magnitudes of these forces. It is found that the forces are greatest when orthotic assistance is needed to compensate for plantar flexor insufficiency in late stance phase. On the other hand, where the AFO is used to support the foot, in the absence of dorsiflexion power in swing phase, the forces are relatively small. Understanding these force levels is relevant to the design of the AFO in terms of choice and use of materials and components.

Download Full-text