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Common methods of measuring feet for orthotics are inaccurate

Telfer S, Gibson KS, Hennessy K, Steultjens MP, Woodburn J. Computer-aided design of customized foot orthoses: reproducibility and effect of method used to obtain foot shape. Arch Phys Med Rehabil. 2012 May;93(5):863–70. PubMed #22541310.
Tags: treatment, orthotics, devices, biomechanics, foot, leg, limbs, pain problems, etiology, pro, self-treatment

PainSci summary of Telfer 2012?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided at the bottom of the page, as often as possible. ★★★☆☆?3-star ratings are for typical studies with no more (or less) than the usual common problems. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.

Foot orthotics are made from basic measurements and captured images of the foot (plaster casting, foam box impressions, or three-dimensional computer images). None of these techniques is very accurate (<80%), especially with measuring the peak arch height. Skilled 3D computer imaging may be the most accurate. Basic measurement is particularly inaccurate.

~ Paul Ingraham

original abstract

OBJECTIVE: To determine, for a number of techniques used to obtain foot shape based around plaster casting, foam box impressions, and 3-dimensional scanning, (1) the effect the technique has on the overall reproducibility of custom foot orthoses (FOs) in terms of inter- and intracaster reliability and (2) the reproducibility of FO design by using computer-aided design (CAD) software in terms of inter- and intra-CAD operator reliability for all these techniques.

DESIGN: Cross-sectional study.

SETTING: University laboratory.

PARTICIPANTS: Convenience sample of individuals (N=22) with noncavus foot types.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Parameters of the FO design (length, width at forefoot, width at rearfoot, and peak medial arch height), the forefoot to rearfoot angle of the foot shape, and overall volume match between device designs.

RESULTS: For intra- and intercaster reliability of the different methods of obtaining the foot shape, all methods fell below the reproducibility quality threshold for the medial arch height of the device, and volume matching was <80% for all methods. The more experienced CAD operator was able to achieve excellent reliability (intraclass correlation coefficients>0.75) for all variables with the exception of forefoot to rearfoot angle, with overall volume matches of>87% of the devices.

CONCLUSIONS: None of the techniques for obtaining foot shape met all the criteria for excellent reproducibility, with the peak arch height being particularly variable. Additional variability is added at the CAD stage of the FO design process, although with adequate operator experience good to excellent reproducibility may be achieved at this stage. Taking only basic linear or angular measurement parameters from the device may fail to fully capture the variability in FO design.

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