Abstract
BackgroundThe foot provides a crucial contribution to the balance and stability of the musculoskeletal system, and accurate foot measurements are important in applications such as designing custom insoles/footwear. With better understanding of the dynamic behavior of the foot, dynamic foot reconstruction techniques are surfacing as useful ways to properly measure the shape of the foot. This paper presents a novel design and implementation of a structured-light prototype system providing dense three dimensional (3D) measurements of the foot in motion. The input to the system is a video sequence of a foot during a single step; the output is a 3D reconstruction of the plantar surface of the foot for each frame of the input.MethodsEngineering and clinical tests were carried out to test the accuracy and repeatability of the system. Accuracy experiments involved imaging a planar surface from different orientations and elevations and measuring the fitting errors of the data to a plane. Repeatability experiments were done using reconstructions from 27 different subjects, where for each one both right and left feet were reconstructed in static and dynamic conditions over two different days.ResultsThe static accuracy of the system was found to be 0.3 mm with planar test objects. In tests with real feet, the system proved repeatable, with reconstruction differences between trials one week apart averaging 2.4 mm (static case) and 2.8 mm (dynamic case).ConclusionThe results obtained in the experiments show positive accuracy and repeatability results when compared to current literature. The design also shows to be superior to the systems available in the literature in several factors. Further studies need to be done to quantify the reliability of the system in clinical environments.
Highlights
The foot provides a crucial contribution to the balance and stability of the musculoskeletal system [1], and accurate foot measurements are important in applications such as designing custom insoles/footwear
The different views usually come from a combination of cameras and projectors. Assessment in this area is usually done by looking at the amount of equipment needed, as well as its reconstruction accuracy and repeatability. When it comes to clinical usability, a primary intent should be to acquire the reconstructions without involving the addition of artifacts to the subjects foot, which could be in the form of markers, socks, paint, and others; abstaining from these additions will ensure the most natural walking patterns possible and provide reconstructions that better reflect the subjects dynamic foot behavior
It is important to note that since the accuracy analysis was obtained with static planar surfaces, the result must be regarded as an experimental upper limit for the accuracy of the system when used with real feet in static and dynamic conditions
Summary
The foot provides a crucial contribution to the balance and stability of the musculoskeletal system, and accurate foot measurements are important in applications such as designing custom insoles/footwear. In order to assess the efficiency and usability of such systems, two factors are of essence, design and implementation, and clinical usability In terms of the former, all systems acquire foot shape using a variation of stereovision, a technique that requires imaging a surface from at least two different views in order to reconstruct its 3D shape [12]. Assessment in this area is usually done by looking at the amount of equipment needed, as well as its reconstruction accuracy and repeatability When it comes to clinical usability, a primary intent should be to acquire the reconstructions without involving the addition of artifacts to the subjects foot, which could be in the form of markers, socks, paint, and others; abstaining from these additions will ensure the most natural walking patterns possible and provide reconstructions that better reflect the subjects dynamic foot behavior. A second important point to consider is the repeatability of the system under clinical trials, to that extent, any design must be able to provide reliable measures of the same foot at different recording times
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