Effect of foot shape on the three-dimensional position of foot bones

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J Orthop Res. 2006 Dec;24(12):2176-86.

Effect of foot shape on the three-dimensional position of foot bones.

Ledoux WR, Rohr ES, Ching RP, Sangeorzan BJ.

RR & D Center of Excellence for Limb Loss Prevention and Prosthetic

Engineering, VA Puget Sound Heath Care System, ms 151, 1660 South

Columbian Way, Seattle, Washington 98108 USA.

To eliminate some of the ambiguity in describing foot shape, we

developed three-dimensional (3D), objective measures of foot type

based on computerized tomography (CT) scans. Feet were classified

via clinical examination as pes cavus (high arch), neutrally aligned

(normal arch), asymptomatic pes planus (flat arch with no pain), or

symptomatic pes planus (flat arch with pain). We enrolled 10

subjects of each foot type; if both feet were of the same foot type,

then each foot was scanned (n = 65 total). Partial weightbearing

(20% body weight) CT scans were performed. We generated embedded

coordinate systems for each foot bone by assuming uniform density

and calculating the inertial matrix. Cardan angles were used to

describe five bone-to-bone relationships, resulting in 15 angular

measurements. Significant differences were found among foot types

for 12 of the angles. The angles were also used to develop a

classification tree analysis, which determined the correct foot type

for 64 of the 65 feet. Our measure provides insight into how foot

bone architecture differs between foot types. The classification

tree analysis demonstrated that objective measures can be used to

discriminate between feet with high, normal, and low arches. ©

2006 Orthopaedic Research Society. © 2006 Orthopaedic Research

Society. This article is a US Government used and, as such, is in

the public domain in the United States of America.