The influence of structural leg length discrepancy on plantar pressure patterns.

Abstract

Aim The aim of the study was to find out whether plantar pressure mapping can be used as a diagnostic tool for mild structural leg length discrepancy by investigating the difference in plantar pressure patterns in structural leg length discrepancy. The plantar pressure patterns of the Experimental group (subjects with at least 10 mm of structural leg length discrepancy) were compared with those of the Control group in order to find out whether a significant difference in plantar pressure (kg/cm2 ) and pressure-time integral (kg*sec) was indeed present.

Methods Ten subjects with a structural leg length discrepancy of at least 10 mm (the Experimental group) and ten subjects without a significant leg length discrepancy( the Control group) were recruited from podiatry clinics from health centres (in the government sector) around Malta. A significant structural leg length discrepancy (or lack of it) was confirmed by carrying out three different measuring techniques. Each subject in the Experimental group was matched with a subject in the Control group by BMI and age. Plantar pressure data was collected as the subjects walked across the Tekscan High resolution pressure mat (South Boston, MA). Peak pressure (kg/cm2 ) and pressure-time integral (kg* sec) values were derived for five foot regions, namely: the hallux, medial forefoot, lateral forefoot, midfoot and heel as well as for the whole foot. Mean pressure values were also calculated for the whole foot.

Results The results showed that there was a significant difference between the peak plantar pressure of the short and long leg, when the foot was divided into regions for all studied groups. No significant difference was present when the test was carried out on the foot as a whole entity of the experimental group (p-value = 0.015) and the midfoot region of the control (p-value = 0.042). It was also found that the midfoot region in the experimental group held no significant difference in pressure-time integral values with a p-value of 0.035. Likewise, significant differences were found in plantar peak pressures and pressure-time integrals between the experimental group and the control group in all the regions of the foot and the whole foot. The highest peak pressure values were: the hallux and the lateral forefoot in the experimental group; the medial forefoot, lateral forefoot and heel in the control group. In all subjects (n=20),the region with the highest peak pressure was the lateral forefoot. The midfoot exerted the least peak pressure. In the case of pressure-time integrals, the highest pressure-time integrals were observed in the heel, lateral forefoot and medial forefoot.

Conclusion From this study it can be deduced that structural leg length discrepancy, despite being very mild has a great influence on the plantar pressure pattern distributions. From the results it can also be concluded that plantar pressure mapping can be held as an appropriate and reliable diagnostic test for structural leg length discrepancy, especially when used in conjunction with other measuring techniques.