Position of the Subtalar Joint Axis and Resistance of the Rearfoot to Supination

2003 ◽  
Vol 93 (2) ◽  
pp. 131-135 ◽  
Author(s):  
Craig Payne ◽  
Shannon Munteanu ◽  
Kathryn Miller
Keyword(s):  
Subtalar Joint ◽  
Sagittal Plane ◽  
Metatarsal Head ◽  
Foot Orthoses ◽  
Joint Axis ◽  
Foot Function ◽  
Two Parameters ◽  
The Relationship ◽  
Clinical Determination

Determination of the position of the subtalar joint axis is being more widely used clinically to facilitate the prescription of foot orthoses and the understanding of foot function, but clinical determination of the axis has not been widely investigated. The aim of this study was to determine the relationship between clinical determination of the subtalar joint axis and the amount of force needed to supinate the foot. The transverse plane position of the subtalar joint axis was determined in 47 subjects. The sagittal plane orientation of the subtalar joint axis was determined using the relative amounts of forefoot adduction and abduction obtained when the rearfoot was supinated and pronated. The amount of force needed to supinate the foot was measured using a device designed to measure resistance to supination. The only two parameters that were correlated to supination resistance of the rearfoot were body weight (r = 0.52) and the perpendicular distance from the fifth metatarsal head to the subtalar joint axis (r = 0.59). The model on which determination of the subtalar joint axis is based may not be valid, but it might help determine how much force is needed to supinate a foot using foot orthoses. (J Am Podiatr Med Assoc 93(2): 131-135, 2003)

The medial heel skive technique. Improving pronation control in foot orthoses

1992 ◽  
Vol 82 (4) ◽  
pp. 177-188 ◽  
Author(s):  
KA Kirby
Keyword(s):  
Subtalar Joint ◽  
New Method ◽  
Foot Orthoses ◽  
Posterior Tibial ◽  
Joint Axis ◽  
Flat Feet ◽  
Foot Orthosis

A new method of foot orthosis modification that enhances the pronation controlling ability of foot orthoses is presented. The medial heel skive technique involves selectively removing small amounts of the medial portion of the plantar heel of the positive cast of the foot to create a unique varus wedging effect within the heel cup of the foot orthosis. The resulting increase in supination moment across the subtalar joint axis of the foot clinically produces significantly improved pronation control on pediatric flexible flat feet, posterior tibial dysfunction, and other types of excessively pronated feet.

Filament Fragmentation Phenomena

1989 ◽  
Vol 170 ◽  
Author(s):  
Juan C. Figueroa ◽  
Linda S. Schadler ◽  
Campbell Laird
Keyword(s):  
Strain Energy ◽  
Stress Transfer ◽  
Fiber Surface ◽  
Yield Information ◽  
The Matrix ◽  
Two Parameters ◽  
The Relationship

AbstractThe effect of fiber surface treatments on the relationship between the tensile strength of a filament and the shear strength of its interphase is one of the central issues facing composite materials technologists today. We demonstrate here that analysis of fragmentation phenomena in monofilament composites can simultaneously yield information about these two parameters. Characterization of shear stress transfer zones in non-critical fragments has led us to the determination of interphase strength.A phenomenological treatment that highlights the role of the matrix in the fragmentation process is presented here. This analysis considers issues such as the strain energy exchange between a failing fiber and the matrix, as well as interphase relaxation due to the viscoelastic nature of the matrix. Our observations of the fragmentation phenomena in AU4/polycarbonate monofilament composites indicate that the fiber/matrix interaction in this system is governed by micromechanical locking.

scholarly journals Three-dimensional Analysis of the Talocrural Joint Axis

2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0003
Author(s):  
Christian Plaass ◽  
Leif Claassen ◽  
Christina Stukenborg-Colsman ◽  
Daiwei Yao ◽  
Kiriakos Daniilidis ◽  
...  
Keyword(s):  
Sagittal Plane ◽  
Articular Surface ◽  
Three Dimensional ◽  
Frontal Plane ◽  
High Standard ◽  
Patient Specific ◽  
Rotational Axis ◽  
Talocrural Joint ◽  
Joint Axis

Category: Ankle Introduction/Purpose: The total ankle replacement (TAR) is increasingly used in cases of severe ankle arthritis. Although the knowledge about joint kinematics is crucial for designing and positioning of TAR there is no consensus about the talocrural joint axis. The aim of the present study was the determination of the kinematic rotational axis of the talocrural joint as an orientation for prosthesis positioning. Methods: We analyzed 96 CT-scans of full cadaver caucasien legs. With the software Mimic, 3-Matic (both Materialize) and GOM inspect we generated three-dimensional reconstruction models of the talus and a best fitting cone orientated to the talar articular surface. The kinematic rotational axis was defined to be the axis of this cone. Results: The determination of the kinematic rotational axis showed a high inter- and intrarater reliability. The kinematic rotational axis of the talocrural joint is orientated from lateral-distal to medial-proximal (84.9° ± 8.5 compared to mechanical tibial axis in frontal plane), from dorsal-proximal to anterior-distal (93.1° ± 42.3 compared to mechanical tibial axis in sagittal plane) and from dorsal-lateral to anterior-medial (169.0° ± 6.7 compared to mechanical tibial axis in axial plane). A high standard deviation especially in the sagittal plane was noteworthy. Conclusion: With the present study we present a new reproducable single-axis model of the talocrural joint. Our data showed relevant interindividual variations. The consideration of these variations might support the development of patient-specific TAR implantation techniques.

Function of the Windlass Mechanism in Excessively Pronated Feet

2001 ◽  
Vol 91 (5) ◽  
pp. 245-250 ◽  
Author(s):  
Anna Aquino ◽  
Craig Payne
Keyword(s):  
Subtalar Joint ◽  
Gait Cycle ◽  
Length Ratio ◽  
Chi Square ◽  
Foot Length ◽  
Joint Axis ◽  
Visual Evidence ◽  
Foot Function ◽  
Axis Position ◽  
Chi Square Analysis

The foot postures of 39 subjects were evaluated for excessive pronation by means of six static weightbearing and five nonweightbearing measurements, and two types of footprint indexes. Visual evidence of windlass function was recorded by video. Chi-square analysis revealed that excessive pronation does not affect the establishment of the windlass mechanism. The position of the forefoot relative to the rearfoot, subtalar joint axis position, and navicular drift/foot length ratio were significantly associated with dynamic windlass function. These results suggest that selected static measurements may have value in predicting some aspects of dynamic foot function during the propulsive phase of the gait cycle. (J Am Podiatr Med Assoc 91(5): 245-250, 2001)

Determination of subtalar joint axis location by restriction of talocrural joint motion

2007 ◽  
Vol 25 (1) ◽  
pp. 63-69 ◽  
Author(s):  
Gregory S. Lewis ◽  
Kevin A. Kirby ◽  
Stephen J. Piazza
Keyword(s):  
Subtalar Joint ◽  
Joint Motion ◽  
Talocrural Joint ◽  
Joint Axis

The Subtalar Angle: A Proposed Measure of Rearfoot Structure

1996 ◽  
Vol 17 (8) ◽  
pp. 499-502 ◽  
Author(s):  
Irene McClay ◽  
James Bray
Keyword(s):  
Subtalar Joint ◽  
Sagittal Plane ◽  
Lateral View ◽  
In Vivo Studies ◽  
Good Reliability ◽  
Mean Values ◽  
Joint Axis ◽  
The Mean

The purpose of this study was to propose a new measure of rearfoot structure to further enhance the understanding of the function of the foot. Landmarks visible on sagittal plane radiographs were used to represent the approximate direction of the subtalar joint axis in the sagittal plane based upon descriptions from the literature of its orientation. Four landmarks were chosen, resulting in four calculated angles. One hundred lateral view radiographs were analyzed. The mean values ranged from 28.7° to 47.7°. These values are within the ranges reported from both cadaver and in vivo studies. Tests of repeatability of the measures resulted in intraclass coefficient values between 0.94 and 0.98, suggesting good reliability. All four angles correlated highly among each other ( r = 0.88–0.97). Examination of the validity of any one of these measures is left to those who are able to accurately calculate the orientation of the subtalar joint axis.

Intratest Reliability in Determining the Subtalar Joint Axis Using the Palpation Technique Described by K. Kirby

2012 ◽  
Vol 102 (2) ◽  
pp. 122-129 ◽  
Author(s):  
Joris De Schepper ◽  
Ken Van Alsenoy ◽  
Johan Rijckaert ◽  
Sophie De Mits ◽  
Tom Lootens ◽  
...  
Keyword(s):  
Subtalar Joint ◽  
Spatial Position ◽  
Biomechanical Analysis ◽  
Clinical Variable ◽  
Foot Orthoses ◽  
Joint Axis ◽  
Exact Determination ◽  
Different Levels

Background: Exact determination and classification of the spatial position of the subtalar joint axis could be a predictive clinical variable in biomechanical analysis and a valuable tool in the design of functional foot orthoses. Methods: Three clinicians with different levels of experience determined and classified the subtalar joint axis location, three times, on 52 individuals, using the clinical palpation, allocation and interpretation technique, as described by K. Kirby. Results: High intratester precision (ICC 0.72 to 0.93) was found for determining the axis location (SEM, 3.72° for angle/0.27 cm for X-axis); however, classification of the spatial position of the axis has large intertester variation (κ = 0.243 to 0.494) Conclusions: The clinical palpation technique itself is reliable; the consistent attribution of a classification, in other words, interpretation, is weak. (J Am Podiatr Med Assoc 102(2): 122–129, 2012)

Stability of Doublet III plasmas against axisymmetric resistive MHD modes

1981 ◽  
Vol 26 (3) ◽  
pp. 431-440 ◽  
Author(s):  
Fred W. McLain ◽  
Torkil H. Jensen
Keyword(s):  
Plasma Current ◽  
Plasma Flux ◽  
Current Profile ◽  
Dimensional Parameter ◽  
Numerical Examples ◽  
Plasma Surface ◽  
Two Parameters ◽  
The Relationship ◽  
Toroidal Geometry

Stability of doublet plasmas in the Doublet III device against resistive axisymmetric MHD modes has been studied. The real characteristics of the device were modelled as accurately as possible. Thus, for example, the actual toroidal geometry was used, the field shaping coils (F-coils) which surround the plasma were included, and the location of real limiters was incorporated for determination of the plasma surface. We have used two parameters to model the plasma current distribution and the equilibrium boundary conditions: one describes the flatness of the current profile, the other describes the fraction of the poloidal plasma flux contained within the separatrix. Thus we have determined stability as a function of these two parameters. If the fluxes at the F-coils are kept fixed, there are stable as well as unstable regimes in this two-dimensional parameter space. If the F-coil fluxes are controlled to imitate the presence of virtual F-coils with fixed fluxes located closer to the plasma, it is possible to stabilize the plasma. This stabilization is discussed in the paper and numerical examples are given. Finally, the relationship between the results of this paper and experimental observations from Doublet III is discussed.

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