Patrick Castagno, M.S.
Freeman Miller, M.D., James Richards, Ph.D.,
Lisa Gaboury, B.S., Nancy Lennon, P.T.
Alfred I. duPont Institute
1600 Rockland Road
Wilmington, Delaware 19803
INTRODUCTION: Pedobarographs are commonly used to measure the pressure distribution histories under the sole of the foot during gait. An objective methodology to assess these pressure distribution histories has recently been described (Miller, et al., 1995). However, the reliability of repeated foot pressure measurements within the same day and between days has not been established. As foot pressure measurements are becoming more widely accepted as a tool in clinical gait analyses, the reproducibility of this test is imperative. The goal of this project was to determine the reliability of bilaterally segmented foot pressure measurements in non-disabled and children with Cerebral Palsy (CP).
MATERIALS AND METHODS: Ten children, five with CP and five non-disabled age matched peers volunteered for this study. Subjects ranged in age from six to sixteen, with a mean age of 9.6 years. Foot pressure measurements were obtained for each subject on both feet for three trials on five separate days. The foot pressure recordings were obtained at a rate of 60hz utilizing a 49cm square floor mat manufactured by Tekscan . Patients were asked to walk across the mat at a self-selected speed, and standard data files were collected using the manufacturer's program. Project-specific software was created to allow the pressure/time histories to be extracted from the area of the mat that contained the full length and width dimensions of the subject's foot. Pressure/time histories from this area were then partitioned into thirds along the longitudinal axis of the foot, and the front two of these partitions were subsequently divided into medial and lateral halves. This provided pressure distributions for five segments including a heel segment, a medial midfoot segment, and a lateral midfoot segment, a medial forefoot segment, a lateral forefoot segment, and total foot. The pressures inside each of these areas were summed, dilated to 100 samples, converted to forces and plotted over time. Intraclass correlation coefficient profiles were created within and between visits to determine the reliability of force/time histories for each section of the foot.
RESULTS: Results indicate that the heel, forefoot, and total areas of the foot produced reliability coefficients greater than 0.7 for within visit and between visit measures for CP and normal subjects (Figure 1 & Table 1). For these sections of the foot, there appears to be little difference in repeatability between the two subject groups or between right and left sides within each group. The midfoot reliability coefficients were more variable and produced reliability coefficients that ranged from 0.587 to 0.921. Overall, the CP group showed better reliability for midfoot measures when compared to the normal group.
Figure 1. ICC profile for Vertical Walking Forces.
Table 1. Mean intraclass correlation coefficients for between and within day measures of foot segmental pressures.
CP Normal
Right Left R&L avg. Right Left R&L avg. Heel .872 .840 .856 .873 .874 .874 Lateral Midfoot .707 .840 .774 .623 .652 .638 Medial Midfoot .847 .835 .841 .587 .602 .595 Lateral Forefoot .827 .765 .796 .868 .821 .845 Medial Forefoot .942 .858 .900 .906 .896 .901 Composite .938 .890 .914 .923 .907 .915 Average .856 .838 .847 .797 .792 .794
Right Left R&L avg. Right Left R&L avg. Heel .849 .897 .873 .943 .898 .921 Lateral Midfoot .780 .862 .821 .843 .814 .829 Medial Midfoot .763 .921 .842 .865 .612 .739 Lateral Forefoot .726 .841 .784 .939 .915 .927 Medial Forefoot .976 .966 .971 .960 .959 .960 Composite .954 .917 .936 .934 .908 .921 Average .841 .901 .871 .851 .914 .883
CONCLUSION: Based on these results, it can be concluded that the force/time histories for both normal and cerebral palsy subjects are reliable for trials obtained within the same visit and trials obtained between multiple visits.
[Return to Table of Contents, Back to Research Symposium Home Page, Orthopaedic Department Home Page,] \