Comparison of two insole materials using subjective parameters and pedobarography (pedar-system)

INTRODUCTION:: The objective of this trial was to investigate two commonly used insole materials prescribed for shock-absorption and cushioning concerning subjective and pedobarographic parameters. The design was prospective, controlled, randomized and single-blinded. MATERIAL AND METHODS:: A convenient sample of six healthy male adults without any history of leg or foot injury or pain wore -- in random order -- the custom-made insoles for one week. For both insoles the same base material (TEPEFON(R)) was used, insole 1 was covered with PLASTAZOTE(R) I, 3 mm, insole 2 with PPT, 3 mm. Both insoles had a metatarsal pad. After one week of wearing, in-shoe plantar pressures, measured at the same time of day and within the same type of indoor tennis shoes (sockliner removed), were obtained using the PEDAR-System(R) (Novel GmbH, Munich, Germany). Before each measurement the PEDAR-insoles were calibrated and the subject walked around for 5 minutes to get aquainted with the device. Three trials were performed for three different conditions and average values were determined: PEDAR-insole alone, with PLASTAZOTE(R) insole, with PPT(R) insole. Data were collected at self selected speed, gait velocity was determined using two optical switches on a 10 m walkway. Pressures were normalized to body weight. Main outcome parameters were 'Maximal Peak Pressure' (MPP) and 'Pressure Time Integral' (PTI). These parameters were determined for the whole footsole, medial and lateral heel, medial and lateral midfoot, medial, middle and lateral forefoot, hallux and toes II-V. Additionally the subjects filled in a questionnaire including: time wearing the insoles daily (in hours), sweating (visual analogue scale -- VAS), wearing comfort (VAS), perceived discomfort (location). Three months after the trial they were asked via telephone call whether they were still using the insoles. RESULTS:: 1. The overall MPP and PTI values did not differ significantly between the PEDAR-insole alone and the investigated inserts. There was a tendency for both insoles towards lower MPP and PTI values in all regions except for the toes, especially for the PPT(R) insole. 2. The questionaire showed a significantly higher wearing comfort for the PPT(R) insole in contrast to the PLASTAZOTE(R) insole, though all subjects sweated more with the PPT(R) material. Four of the six subjects experienced discomfort due to the metatarsal pad within the PLASTAZOTE(R) insole, only one within the PPT(R) insole. 3. None of the subjects continued to use the PLASTAZOTE(R) insole, but three continued to use the PPT(R) insoles. DISCUSSION:: Despite the significant differences in the subjective parameters, especially wearing comfort, no statistical significant difference for the overall MPP and PTI values between the PEDAR-insole alone and the investigated insoles or in between the insoles tested could be obtained. Yet there was a tendency for both insoles to lower MPP and PTI values in all regions except for the toes. This might be due to the thickness of the insoles and the reduced space within the toe box. The subjectively better tolerated PPT(R) insole tended to lower MPP and PTI more than the PLASTAZOTE(R) insole. CONCLUSION:: Wearing comfort and pedobarographic outcome measurements did not correlate significantly in this trial. Yet there was a tendency for the subjectively better tolerated PPT(R) insole to lower MPP and PTI more.