June 2010

Experts advocate pressure measurement utilization to improve orthotic outcomes

Photo courtesy of Tekscan

Fancy camera systems not required

A pressure measurement system is an essential clinical tool for maximizing orthotic outcomes that too many practitioners are not yet utilizing, according to two presentations at the FIP meeting in Amsterdam.

Pressure mapping can quantify the effects of an orthotic intervention, alerting the practitioner immediately as to whether any further adjustments might be needed. The same technology can be used pre- and post-operatively to assess whether a surgical intervention has had the desired results. And some clinicians might be surprised to learn that this can be done without the need for expensive three-dimensional multi-camera motion analysis systems.

“If we only use pressure measurement can we predict the motion of the foot? Yes we can,” said Paul van Neerven, a podotherapist in the Amsterdam suburb of Zeist. “That is only for movement of the foot. If you need to look at movement of the knee or higher up, you will need video. My opinion is that when you have a sports podiatry practice you need video, but if you don’t have a sports podiatry practice then you don’t need it.”

Jeffrey Ross, DPM, MD, associate clinical professor of medicine at Baylor College of Medicine and chief of the diabetic foot clinic at Ben Taub County Hospital, both in Houston, TX, spoke at the FIP meeting about the use of pressure measurement for orthotic treatment of patients with diabetes, but said the same concepts could be applied to sports medicine or other clinical areas.

For patients with diabetes in particular, Ross identifies areas of high pressure as potential ulceration sites, then looks for pressure reductions at those sites once orthoses have been fitted. He also uses pressure measurement to analyze pressure-time integral (PTI), since duration of plantar loading is as important as magnitude.

In one example, he showed that orthoses decreased peak pressure at a particular site from 61 psi to 42 psi. In another example, PTI decreased from 26.6 psi/sec to 9.9 psi/sec.

“Based on the scan data, we can find a better treatment and reduce the amount and time of loading of the forefoot by redistributing the pressure and offloading the forefoot,” Ross said. “Once we put in a functional orthotic, we can eliminate that high pressure and excessive time.”

Van Neerven described a case in which a patient with plantar fasciitis was given an orthotic device that had been corrected by about 4°, lifting the medial arch to relieve tension on the fascia. But a pressure scan showed that in fact the plantar pressure was still elevated medially, so that the orthosis was not providing the desired relief. After the device had been adjusted with a cut-out under the first metatarsal head, a subsequent pressure scan showed that the pressure distribution had lateralized.

“By just using a mat you can see what the foot does with your insole therapy,” van Neerven said. “If the insole is not good, you can correct it immediately. If I don’t, then the patient will have to come back another time, so it’s better to do it at one time.”

In patients with diabetes, pressure measurement might save a patient more than time. It might save his or her limb.

“We have a way to try to intervene ahead of time by looking at the etiology,” Ross said. “I’m not looking at where the problem is now, I’m looking at where it came from and where it’s going.”

A German study comparing bonded and vulcanized insoles found that 470 km of running had surprising effects on each.

Researchers from the Munster University of Applied Sciences compared the two manufacturing techniques on a single runner, who wore a bonded insole on his left foot and a vulcanized insole on his right foot. The mechanical properties of the insoles and the associated heel pressures were assessed after one week of wear and again after six weeks, by which time they had been subjected to 470 km of distance running.

The thickness and density of the vulcanized insole did not change. The soft upper layer of the bonded insole decreased in thickness by nearly half, but the density increased by only 8%, suggesting a molecular change that may be related to sweating, according to researcher Klaus Peikenkamp, PhD, who presented the findings at the ISPO meeting in Leipzig.

Also surprising was that despite the decreased thickness, the mean heel pressure associated with the bonded insole remained almost constant (8.9 N/cm2 vs 9.0 N/cm2). Meanwhile, the mean heel pressure under the vulcanized insole increased over time (from 7.8 N/cm2 to 8.3 N/cm2) even though the thickness and density did not change, perhaps suggesting adjustments in running pattern made by the subject to reduce the interlimb asymmetry, Peikenkamp said.

“We have to consider that the results were based on one subject only,” he said. “However, there are some surprising ones.”

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