The Bergmann Foot Scanner and automated design system has two distinct functions. One function is the ability to capture the
foot and change it into a digitized form that can be evaluated, shown on a computer and used in the production of a functional orthotic
device. The second function is the ability of the pedorthist to precisely manipulate and change the shape of this digitized
data to form more accurate cast corrections so that an orthotic fabricated using this digitized image will be both more comfortable
and effective in controlling the patient's biomechanical condition. Secondarily, but no less important, the system helps to
explain the basics of biomechanics to patients and others in a clear and concise way, and it has the ability to evolve into a research
tool that can be used to expand and verify our knowledge about orthotics and biomechanics.
In the realm of orthotic automation,
there are currently two methods of capturing the image of the foot, contact and non contact digitization.
Contact Digitization
This method uses a probe to collect data on the foot and a computer to analyze the data. As
this method requires numerous samples to accurately capture the image of the foot, most systems using this technology spread out the
data samplings to get a basic contour of the plantar aspect of the foot. This image is then compared to previously stored digitized
foot shapes until the closest match is found. In essence, this is like fitting a wide range of prefabricated orthotics to the
patients foot until one is found that matches that foot the closest. At best this is a poor representation of custom design.
Non Contact Digitization
Non-contact digitization, in use in the Bergmann scanner, consists of a video camera, a
light source (optical laser) and a computer to analyze the date. Data samplings are obtained every 40 thousandths of an inch,
giving a very detailed representation of the contour of the foot. And subsequently, orthotics will fit precisely to the foot
shape. It is very important to note that an automated orthotic is only as accurate as its least accurate measuring point.
The least accurate point is the image capture. If data samplings have been taken 1/4 of an inch apart, then orthotic accuracy
is 1/4 of an inch. Even if milling processes are accurate to a tenth of a thousandths of an inch, the orthotic will only be
accurate to 1/4 of an inch because that was the image capture resolution. The Bergmann scanner takes about 9000 data samplings
of the plantar, medial and lateral aspects of the foot, in about six seconds. In comparing plaster casting to optical casting,
both methods rely on the clinician holding the foot in the correct neutral position for accuracy. Both methods give an accurate
three dimensional contour of the foot. Plaster casting is total contact, and optical casting is a data sampling every 400 hundredths
of an inch. Optical casting has been found to be, overall, more accurate because the clinician can more precisely check the
optical scan on the computer to see if it corresponds to the biomechanical examination. If discrepancies are apparent, another
scan be taken with little effort and waste of time.
