| Summary: | 碩士 === 國立臺灣大學 === 物理治療學研究所 === 92 === Plantar fascia is the main load-bearing structure beneath the foot, which is noted to be vulnerable to excessive or abnormal stress acting on it. It is essential to study the mechanical properties of the plantar fascia to reveal the patho-mechanism of plantar fasciitis. In the past, researchers explored the mechanical properties of the plantar fascia via in vitro methods, which may not be able to reflect the properties of the fascia in a living system. The only in vivo study used the fluoroscopy, a series of X-ray, to obtain the image of the foot. This method may risk the participants in radiation exposure, avoided this method to be widely or repetitively used in the clinic.
It is, therefore, necessary to develop a method to detect the mechanical properties of the plantar fascia. To measure the resonance frequency of the plantar fascia and to clarify the relationship between the resonance frequency and the load acting on the foot, 13 healthy young participants were recruited in this study. A vibrator mounted with accelerometer was attached to the dorsum of the foot. The Doppler ultrasonography was used to detect the vibration speed of the plantar fascia beneath the foot. Through the acceleration of the vibrator detected by the accelerometer and the speed of the vibrating plantar fascia from the Doppler ultrasonography, amplitudes of vibration of the vibrator and the plantar fascia could be determined. By dividing the amplitude of the plantar fascia by the amplitude of the accelerometer, the resonance frequency of the plantar fascia was determined as the peak value of the frequency spectrum. The reliability was tested in the standing condition repetitively. The intra-class correlation coefficient (ICC) and the standard error of measurement (SEM) were used to represent the reliability of the test. The resonance frequency was also detected for the sitting, standing, and loaded conditions. For the sitting condition, participants were asked to sit on a high chair with their foot place on the platform. Their hands were not allowed to place on their thighs to avoid unexpected loads on the foot. For the standing condition, the participants were asked to stand on two acrylic testing platforms with their feet apart at shoulder width and to keep their trunk upright when the data were collected. The loaded condition was the same as the standing condition except the participants were asked to wear a weight jacket in order to create a loaded condition of 50% of body weight on the body. ANOVA with repeated measures was used to examine the differences of various loading conditions. Level of significance was set at ?.05 and the differences were considered as significant. If any significance was noted from the ANOVA with repeated measures, the post-hoc comparisons were performed for each two conditions and level of significance was adjusted to ?= .05 / 3 = .0167.
The results showed that the reliability was at fair to good level. The resonance frequency was 20.4�b1.2 Hz for the sitting condition, 25.4�b1.0 Hz for the standing condition, and 27.5�b1.1 Hz for the loaded condition, respectively. There was significant difference between the sitting and the standing condition (p<0.001) and between the sitting and the loaded condition (p<0.005) but not between the standing and the loaded condition.
The present study provided an innovative method to detect the resonance frequency of the plantar fascia in vivo. Before it can be served as clinical implementation, further research should be directed to investigate the relationship between the resonance frequency and plantar fasciitis, and to establish the normal value of the resonance frequency of the plantar fascia.
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