Trimline Severity Significantly Affects Rotational Stiffness of Ankle-Foot Orthosis

Bielby, Shea A.; Warrick, Tim J.; Brooks, R. L.; Skewes, E; Alvarez, Estefania; Dunning, Christopher; DesJardins, John D.

doi:10.1097/jpo.0b013e3181f9082e

Cited by 17 publications

(16 citation statements)

References 9 publications

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“…Therefore, the challenge in the design process of an AFO is to be able to provide a desired range of motion with minimal stress concentration over the material. Bielby et al [17] designed three different trimlines (conservative, moderate, aggressive approaches) in the medial and lateral sections of the orthosis at different depths and compared the stiffness of the AFOs. The models with different trimline depths resulted in significantly different stiffness measures, except for the moderate and aggressive cuts along the transverse plane.…”

Section: A Novel Dorsal Trimline Approach For Passive-dynamic Ankle-fmentioning

confidence: 99%

A Novel Dorsal Trimline Approach for Passive-Dynamic Ankle-Foot Orthoses

Sürmen¹,

Akalan²,

Fetvaci³

et al. 2018

SV-JME

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An ankle-foot orthosis (AFO) is an externally applied assistive device that encompasses the lower leg, ankle, and foot of the human body. In the current one-piece passive-dynamic AFO design, the trimming process is performed from lateral and medial parts of the ankle to ensure desired rotational displacement (hereafter referred to as Design I). In most cases, stress concentrations occurring over the trimmed regions during walking can cause permanent damage to the AFO. In this study, to reduce the stress concentration and ensure a homogeneous stress distribution, a new trimming approach is presented, in which the trim zones were transferred from lateral and medial to dorsal (hereafter referred to as Design II). Finite element analyses of the Designs I and II models were carried out. Displacement and von Mises stress values for both models under the same loading and boundary conditions were obtained. Maximum displacement values were 8.51 mm and 9.05 mm for Design I and Design II, respectively. Maximum stress values were 15.19 MPa and 6.70 MPa for Design I and Design II, respectively. For the similar range of motion of ankle joint, the novel design produced less stress and more homogeneous stress distribution than the currently used design, thus indicating that Design II would be more resistant to plastic deformation than Design I.

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Section: A Novel Dorsal Trimline Approach For Passive-dynamic Ankle-fmentioning

confidence: 99%

A Novel Dorsal Trimline Approach for Passive-Dynamic Ankle-Foot Orthoses

Sürmen¹,

Akalan²,

Fetvaci³

et al. 2018

SV-JME

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“…Given the same type of thermoplastic the stiffness is directly related to structure characteristics such as thickness of the wall, 8 and position of the trimline in solid AFOs. [9][10][11] In clinical practice, tremendous effort is made to align the joint of AFO with respect to the anatomical ankle joint (i.e. talocrural joint) as close as possible.…”

Section: Introductionmentioning

confidence: 99%

Effects of joint alignment and type on mechanical properties of thermoplastic articulated ankle-foot orthosis

Gao

Carlton

Kapp

2011

Prosthetics &Amp; Orthotics International

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Background: Articulated or hinged ankle-foot orthosis (AFO) allow more range of motion. However, quantitative investigation on articulated AFO is still sparse. Objective: The objective of the study was to quantitatively investigate effects of alignment and joint types on mechanical properties of the thermoplastic articulated AFO. Study design: Tamarack dorsiflexion assist flexure joints with three durometers (75, 85 and 95) and free motion joint were tested. The AFO joint was aligned with the center of the motor shaft (surrogate ankle joint), 10 mm superior, inferior, anterior and posterior with respect to the motor shaft center. Methods: The AFO was passively moved from 20 plantar flexion to 15 dorsiflexion at a speed of 10 /s using a motorized device. Mechanical properties including index of hysteresis, passive resistance torque and quasi-static stiffness (at neutral, 5, 10 and 15 in plantar flexion) were quantified. Results: Significant effects of joint types and joint alignment on the mechanical properties of an articulated thermoplastic AFO were revealed. Specifically, center alignment showed minimum resistance and stiffness while anterior and posterior alignment showed significantly higher resistance and stiffness. The dorsiflexion assist torques at neutral position ranged from 0.69 AE 0.09 to 1.88 AE 0.10 Nm. Conclusions: Anterior and posterior alignment should be avoided as much as possible. Clinical relevanceThe current study suggested that anterior and posterior alignment be avoided as much as possible in clinical practice due to potential skin irritation and increase in stress around the ankle joint.

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“…3, b) but is still quite similar for all the AFOs. The further reduction of the distance between fixture and loading points leads to rapid growth of stiffness and its scatter (6,(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)3 and 28,4-57,6 N/mm for forces F3 and F4 on scheme Fig. 3, b correspondingly).…”

Section: Resultsmentioning

confidence: 99%

“…The same approach is also used when developing exoskeletons [13,14]. The above mentioned researches and AFOs stiffness investigations under static [15][16][17][18][19] and dynamic [20,21] loading lead us to the conclusion, that along with AFOs overall parameters (strength, longevity, comfort and ease of use etc. ), their stiffness has a special interest of their manufacturers and therapists.…”

Section: Introductionmentioning

confidence: 99%