The goal of this project was to develop knowledge and quantitative methods and measurement devices for effective, expeditious, repeatable, and consistent design and manufacture of well-fitting, comfortable, and functional orthopedic footwear. The specific objectives of the project were: (1) to develop a 3-D optical digitizer capable of rapidly and accurately digitizing the spatial geometry and surface topography of peoples' feet and ankles in natural and prescribed alignments, in partial and full weight bearing states, preserving the location of anatomical fiduciary landmarks, and laboratory and clinically test the digitizer on 12 subjects; (2) to evaluate the fit of US Military Women's Lasts and the corresponding footwear manufactured there from on female personnel; (3) to derive measures quantifying footwear fit; (4) to measure the effects of nine commonly prescribed orthopedic footwear components and modifications on people's pedal/shoe interface stresses and strains; and (5) to measure the mechanical properties of materials commonly used to make orthopedic insoles.

I. Define Foot Measurements
II. Foot and Last Variations
III. Data Analysis
IV. Result

Our standard foot measurements

Total length (Lt): The total length from heel to toe end;
Ball length (Lb): The length measured from heel to middle of the ball;
Ball width (Wb): The width measured from the first metatarsal joint to the fifth metatarsal joint;
Ball Girth (Gb): The circumferential length measured around the ball width line;
Heel Width (Wh): The heel width is the maximum width measured at vertical sector that is 0.3 * Lb away from the end of heel and at height no more than 0.25 * Lb;
Heel Width 2 (Wh2): The heel width 2 is measured at the same vertical sector at the height equal to 0.25 * Lb;
Instep Height (Hi): The height is measured at the vertical sector that is 0.7 * Lb away from heel;
Instep Width (Wi): The width is measured at the same vertical sector as instep height;
Toe (box) height (Ht): The height is measure at the vertical sector that is 1.25 * Lb away from heel.
To make comparison easy, all measurements are normalized to its ball length. For example: the total length is Lt, the normalized total length is Lt / Lb, i.e. total length divided by the ball length.back to top

Foot width may vary from narrow to wide.

The ratio of ball width and heel width changes from person to person. A large value of the ratio indicates a V-shape foot while a small value indicates a U-shaped foot.

Instep height varies from low to high

US military lasts have width from AAAAA (narrowest) to EEEEE (widest). back to top

Plot of normalized ball width vs heel width. The foot data points are shown as black diamond; US military lasts (from AA to EEEEE) are shown as blue upward triangles; The suggested U-V shaped lasts are shown as red downward triangles.

Here we define a measurement: Total Fitting Error (Et) in millimeters for shoe fitness. The total fitting error including three components:
(1) Heel Fitting Error: Eh = last heel width - foot heel width, with an extra condition: any last has Eh < -2 mm must be excluded (too tight);
(2) Ball fitting Error: Eb = last ball width - foot ball width, any last has Eb < -1 mm must be excluded (too tight);
(3) Length Error El = Last Length -desired last length (foot length + 12 mm), again any last has El < -2 must be excluded.
The total fitting error is defined as
Et = square root (Eh x Eh + Eb x Eb) + 0.5 x El
Where the square root of (Eh x Eh + Eb x Eb) is the distance from foot point to nearest last point in figure

The plot shows the percentage of population can fit shoes using (a) single width last; (b) current US military lasts; (c) suggested U-V shaped lasts. It indicates without increasing the cost, i.e. using the same number of last, U-V shaped lasts can fit more people at the same level of fitting error than US military lasts. back to top

Result

144 US military footwear Lasts were digitized with the optical digitizer, and the resulting measurement files entered into the VA NYHHS Pedorthic CAD System Last Library, and into the project pedorthic database. Optical scans and manual measurements of the feet and ankles of 51 normal, healthy female and 50 healthy male test subjects of military service age, were acquired and used in quantitative assessment of military footwear/Last fit. Analysis of the scans and measurements showed that US Military Lasts/footwear properly fit only one third of the subjects.

Many commercially available shoes come one width per size. This study shows for "one width fit all shoes" to fit 64% study subject, people have to accept 12 mm of total fitting error. While army last serial last can fit 64% of subject with about 5mm total fitting error. The data shows the army last serial seems shifted to narrow side. The lasts narrower than AA do not fit any subject while EEEEE last is still not wide enough to fit some wide feet. Another problem of the army last serial is that does not address the issue of the U-shaped and V-shaped feet. An improvement maybe needed to fit U-shaped and V-shaped feet better.

The results showed that new Last designs, incorporating multiple heel widths in addition to heel-to-toe length and metatarsal ball width sizes, are needed to make footwear for US military personnel. An initial "U-V" design scheme for such Lasts was developed based on the pedal anthropometric measurements acquired in the project. back to top