June 2017

INSOLE MODELING: Computer analysis facilitates foot orthosis development

By Jordana Bieze Foster

Computer modeling is facilitating advances in insole development for patients with diabetic neuropathy and rheumatoid arthritis, according to data presented in May at the 2017 ISPO World Congress in Cape Town, South Africa.

Researchers from the UK have pioneered the use of finite element analysis (FEA) in creating models of the foot on which to base plantar pressure-based insole design, in 2016 publishing a simplified version of the process to make it more clinically useful.

More recently, in 18 patients with diabetic neuropathy, the investigators compared the effects on plantar pressure of insoles made using three different techniques: the standard method involving a foam box and CNC (computerized numerical control) manufacturing, a method involving FEA-based design and CNC manufacturing, and a third method involving FEA and 3D printing.

Before the intervention, all patients had significantly elevated plantar pressures under the metatarsal heads but no active foot ulcers. When the insoles were worn, the devices created using the two FEA-based methods were associated with significantly greater reductions in those plantar pressures than the conventional method.

“We feel we’ve made some promising insights with regard to moving this forward,” said James Woodburn, PhD, interim director of the Institute for Applied Health at Glasgow Caledonian University, who presented the preliminary findings in Cape Town.

Researchers from Aalborg University in Denmark are using a different type of modeling—using patient-specific bone geometry based on magnetic resonance imaging—to determine the effect of patient-specific insoles on ankle mechanics in patients with early stage rheumatoid arthritis.

In four women, the investigators found that the optimized insoles were associated with lower ankle plantar flexion moments during stance phase and toe-off, as well as less soleus muscle force—all of which could help decrease pain—compared with a control insole from a running shoe.

Sources:

Woodburn J. Precision orthotics to improve the effectiveness of orthopedic assistive devices: foot orthoses. Presented at the International Society of Prosthetics & Orthotics World Congress, Cape Town, South Africa, May 2017.

Telfer S, Erdemir A, Woodburn J, Cavanagh PR. Simplified versus geometrically accurate models of forefoot anatomy to predict plantar pressures: a finite element study. J Biomech 2016;49(2):289-294.

Simonsen MB, Naesborg-Andersen K, Kowalski MR, et al. Patient-specific musculoskeletal modelling of foot orthotics effect on rheumatoid arthritis patients ankle joint loading. Presented at the International Society of Prosthetics & Orthotics World Congress, Cape Town, South Africa, May 2017.

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