Trouble Underfoot: 3D Scanning and Printing the Next Step in Alleviating Foot Pain

Dustin Hoffman’s portrayal of down-and-out Ratso Rizzo in Midnight Cowboy (Best Picture, 1970) earned him a nomination for best actor. Had he won, he might have thanked a pebble in his acceptance speech.

The only X-rated movie to ever win Best Picture, Midnight Cowboy left the world with unshakeable, gritty depictions of a desperate class of people in New York eking out a living, hustling, stealing and scamming the rich and well-off. Ratso is also unforgettable for a permanent limp, which Dustin Hoffman had to portray for all the days of filming. Once he put a pebble in his shoe, he no longer had to think about it. That was enough to change his gait, his mannerisms—and make him an entirely different person.

Those with foot problems can relate. A painful foot changes everything.

Go ahead, you won’t break it. Tiger 3D scanner has a total of nine cameras—some mounted vertically on each side, the rest underneath—to take accurate 3D measurements of the weighted foot. (Picture courtesy of RSscan.)

Foot Care Then. It’s a Grind.

Corrections or compensations for biomechanical irregularities, from injuries or inherited, have been attempted for thousands of years. There is evidence of wool or felt being placed in ancient shoes. Craftsmen have plied a trade in custom-created shoes and inserts for hundreds of years. Today’s orthopedic industry credits an orthopedist who, during 1905 in Boston, placed a metal support under fallen arches as the birth of the modern orthotic industry. That device was replaced by lighter metal insoles by Dr. William Scholl in 1910, who went on to create numerous foot-care products for the company that bore his name, whose cut-and-insert foam liners hang in every drugstore.

It doesn’t even have toes. The tools of the trade include a wooden last, a grossly simplified copy of a patient's foot that has been used to fashion an orthotic for hundreds of years. Custom orthotics have been the work of craftsmen who starting with plaster, foam, wood. They use shapers, cutters, grinders to make the last as well as the orthotic. It would take infinite skill and patience to make a block into the complex shape of a foot so they settle on a rough shape that is somehow representative of the human foot. The last is used to impress what will be the orthotic insert or shoe sole. (Picture courtesy of Bayer.)

While cut-and-insert insoles offer some degree of customization, more is offered by inserts that are custom fit to an individual’s feet. The made-to-order orthotics industry is projected to grow to $1.7 billion by 2022, according to Statista.

Moving Parts

While this shape is only a gross approximation of a foot, even Michelangelo would have been no help with an accurate carving of a foot from a resting or standing model. Under a static load, the metatarsals splay, making the foot wider. The flesh spreads underneath phalangeal joints (ball of the foot) and the calcaneus (heel bone). The arch falls. Walking or running relies on 26 bones with 20 articulated joints. Toes go every which way. Pressure points form and disappear.

Under pressure. Center of pressure line calculated from pressure contours. Knowing the area where pressure occurs will help make an orthotic that is able to relieve it. (Picture courtesy of RSscan.)

To create an effective orthotic from a model of an unweighted foot model has been an art rather than a science. The sculptor/technician/podiatrist uses their knowledge of foot loading and dynamics to transform the foot last (called the positive) and/or the impression (the negative) to fashion the insole and in the end, give some relief to the patient.

It is a process in need of transformation, a dose of technology.

Foot Care of the Future—Enter HP

For Elaine Tara, and many like her, bunion surgery has left lingering discomfort. Off the rack orthotic insoles have been no help. Here, she walks on a foot pad that records pressure gradients in her foot in the hope of getting a custom made orthotic that relieves pressure points.

Enter HP, a company that has chosen to have Innovate as their tag line, like they mean it. As an example, they intend to take the lowly foot and elevating it to tech star status.

At its annual convention, the America Academy of Pediatric Sports Medicine near Fisherman’s Wharf in San Francisco, Paul Linton of Go 4-D, Inc., shows how his equipment changes everything. Go 4-D is a reseller of FitStation, powered by HP.

Paul Linton, CEO of Go 4-D, Inc. No one has put scans of weighed and unweighted feet together to solve the orthotics problem, he says.

A Tiger 3D foot scanner has nine cameras behind glass that move front to back of the foot of a seated patient, all the time taking images that create a 3D mesh model. A separate walk pad about 6 feet long records the forces as the patient walks. Pressure readouts from the walk pad are combined with gait analysis and the scanned model automatically (though exactly how this is done is not sufficiently clear at this point).

This is a way more accurate method, says Linton. The craftsman’s idea of a loaded foot and what its orthotic should be shaped was largely a matter of conjecture because the foot model was made from an unweighted foot.

Another technology unavailable to the old-world craftsman was 3D printing. We have that too, says Jim Christensen of HP, referring to their Jet Fusion 3D printing systems. The exact shape of the orthotic comes out of the Go 4-D system with an STL file which is sent directly to the 3D printer.

Limp Not, Waste Not

The savings in materials is enormous, say Linton and Christensen. The 50-year, laborious and wasteful tradition of making casts and mold can end with our approach.

We learn how involved it was. The patient first has a plaster cast made of their foot. The plaster cast is used to make the foot model, then discarded. The foot model is pressed into material to make the mold for the orthotic. The foot model, having served its purpose, may be stored for some time, but is eventually discarded. Same for the mold into which the orthotic material is poured. All these processes take time and all the material costs money.

By contrast, Go 4-D will take a digital model of the foot and use it to create a matched surface on an orthotic that is 3D printed. The only material used is the cup full of powder in the 3D printer. All the powder that is not fused together to make the orthotic is used in the next build.