The pedograph as a window to the gait cycle
Have you ever studied footprints on the beach or looked at the print left by a wet foot when you get out of the water? These are some of the most primitive types of pedographs.
The pedograph, 1st described by Harris and Beath in 1947 is a rubber mat surface with multiple protruding, small grid lines on one side, which, when covered with ink, imprints an underlying sheet of paper when weight (usually a foot) passes over it. Relative plantar pressures are indicated by the size and density of the inked area, creating a “footprint” reflecting passages of force through the foot at that instance in time. They have fallen into and out of usage over the years, often discarded for more expensive technology such as pedobarographs, individual pressure sensors, and pressure sensitive mats, which have computer interfaces and can provide many useful measurements and calculations to assist the clinician with rendering a diagnosis. These systems, though more precise in some ways (provided a controlled, reproducible testing procedure) are often thousands of dollars, require a computer and the necessary skills, and have a substantial learning curve.
The pedograph in contrast is simplistic, inexpensive, and reliable and only requires that the user have an intact visual pathway and cerebral cortex and knowledge of the events occurring in the gait cycle. With some practice and a good knowledge base, the subtle nuances detected by the sensitive pedograph (nuances that can be undetected with high end computer driven plantar pressure devices) can offer information critical to a precise diagnosis and give solid clues to gait flaws and compensations. With minimal training using a pedograph, reproducible “prints” can be produced for analysis, in light of your findings clinically. They also make wonderful educational tools for your patients and clients!
An essential part of a comprehensive patient evaluation should include examination of the entire kinetic chain both in a static and dynamic fashion. Often what you see statically is either directly translated to or compensated for in the dynamic evaluation. (It is important to note that many of the available foot scan units available from orthotic companies scan a patient in a static standing position and give little information on how the feet and lower limb dynamically engage the ground during movement.) The pedograph is a useful visual tool representing a 2 dimensional image of tridimensional motion, and you are seeing the end product and compensation (or lack thereof) of the individuals mechanics at that point in time. Because of the specificity of what you are seeing refers to a particular point in time, technique and reproducibility are of paramount importance. Prints should be performed several times to insure what you are looking at is what you are looking at, and not movement artifact, because of the way the patient stepped on to or off of the mat.
With a pedograph, seeing is believing. When you have objective data about how an individual moves through space and how their joints and motor system help them to accomplish that, you have a better appreciation for the type or form of therapy which may be most appropriate. In the hands of a skilled clinician, seeing abnormal plantar pressures tells you where the biomechanical fault lies, and thus where manipulation may be appropriate, which muscles need strengthening and where neuromotor coordination is lacking and gait rehabilitation is needed.
excerpted from the 1st edition of our Book “Pedographs and Gait Analysis: Clinical Pearls and Case Studies” Trafford Publishing