TY - JOUR
T1 - A quantitative analysis of optimum design for rigid ankle foot orthoses
T2 - The effect of thickness and reinforcement design on stiffness
AU - Chatzistergos, Panagiotis E.
AU - Eddison, Nicola
AU - Ganniari-Papageorgiou, Evangelia
AU - Chockalingam, Nachiappan
N1 - Publisher Copyright:
© 2023 International Society for Prosthetics and Orthotics.
PY - 2024/4/1
Y1 - 2024/4/1
N2 - Background: An ankle foot orthosis (AFO) which is prescribed to be rigid should only deform a small amount to achieve its clinical goals. Material thickness and the design of reinforcing features can significantly affect AFO rigidity, but their selection remains based on anecdotal evidence. Objectives: To quantify the effect of these parameters on AFO stiffness and to set the basis for quantitative guidelines for the design optimisation of rigid AFOs. Study design: Experimental and computational study. Methods: A polypropylene AFO was produced according to UK standard practice and its stiffness was experimentally measured for 30Nm of dorsiflexion. Its geometry and mechanical characteristics were utilised to create a finite element (FE) model of a typical AFO prescribed to be rigid. Following validation, the model was used to quantify the effect of material thickness and reinforcement design (i.e., reinforcement placement, length) on stiffness. A final set of AFO samples was produced to experimentally confirm key findings. Results and conclusions: For a specific AFO geometry and loading magnitude, there is a thickness threshold below which the AFO cannot effectively resist flexion and buckles. FE modelling showed that stiffness is maximised when reinforcements are placed at the anterior-most position possible. This key finding was also experimentally confirmed. The stiffness of an AFO reinforced according to standard practice with lateral and medial ribbing was 4.4 6 0.1 Nm/degree. Instructing the orthotic technician to move the ribbings anteriorly increased stiffness by 22%. Further stiffening is achieved by ensuring the reinforcements extend from the footplate to at least two-thirds of the AFO’s total height.
AB - Background: An ankle foot orthosis (AFO) which is prescribed to be rigid should only deform a small amount to achieve its clinical goals. Material thickness and the design of reinforcing features can significantly affect AFO rigidity, but their selection remains based on anecdotal evidence. Objectives: To quantify the effect of these parameters on AFO stiffness and to set the basis for quantitative guidelines for the design optimisation of rigid AFOs. Study design: Experimental and computational study. Methods: A polypropylene AFO was produced according to UK standard practice and its stiffness was experimentally measured for 30Nm of dorsiflexion. Its geometry and mechanical characteristics were utilised to create a finite element (FE) model of a typical AFO prescribed to be rigid. Following validation, the model was used to quantify the effect of material thickness and reinforcement design (i.e., reinforcement placement, length) on stiffness. A final set of AFO samples was produced to experimentally confirm key findings. Results and conclusions: For a specific AFO geometry and loading magnitude, there is a thickness threshold below which the AFO cannot effectively resist flexion and buckles. FE modelling showed that stiffness is maximised when reinforcements are placed at the anterior-most position possible. This key finding was also experimentally confirmed. The stiffness of an AFO reinforced according to standard practice with lateral and medial ribbing was 4.4 6 0.1 Nm/degree. Instructing the orthotic technician to move the ribbings anteriorly increased stiffness by 22%. Further stiffening is achieved by ensuring the reinforcements extend from the footplate to at least two-thirds of the AFO’s total height.
KW - AFO
KW - dorsiflexion
KW - finite element modeling
KW - orthoses
KW - stiffness
UR - http://www.scopus.com/inward/record.url?scp=85190394253&partnerID=8YFLogxK
U2 - 10.1097/PXR.0000000000000247
DO - 10.1097/PXR.0000000000000247
M3 - Article
C2 - 37314325
AN - SCOPUS:85190394253
SN - 0309-3646
VL - 48
SP - 204
EP - 212
JO - Prosthetics and Orthotics International
JF - Prosthetics and Orthotics International
IS - 2
ER -