A quantitative method for comparing external foot shapes has been developed and evaluated for potential application to custom shoes/orthoses and orthopedic research. The system employs a laser scanner and custom software to obtain more than 16,000 points (every 3 degrees radially, every 2 mm proximal-distal) over the entire foot (dorsal and plantar aspects). The high-resolution images are transferred to a computer workstation where the foot shapes are aligned, compared and relative differences between the shapes are graphically displayed. The accuracy, reproducibility and performance of the foot comparison system are well within the tolerances required for clinical use. When comparing measurements on objects of known size and shape to those determined by the system, the maximum aggregate system error (both hardware and software) was less than 1 mm. The numerical algorithm for digital alignment of scanned feet is reproducible to 1 degree and .01 mm translation. The average computer time for comparison of scanned images in this study was 10 seconds; the entire process, including digitizing, took less than 15 minutes. Although this system unrealistically treats the foot and shoe as rigid entities, it is consistent with the goal of providing shoes and insoles that reduce the risk of ulceration in insensate feet during shoe break-in or normal activity.
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Borchers et al. (1995) studied this question.