OFF-THE-SHELF IN-SHOE HEEL INSERTS: THEIR EFFECTS ON THE FOREFOOT

Abstract

Introduction: Off-the-shelf heel inserts are used widely without adequate scientific information regarding their effects under the forefoot and this study was aimed to fill this paucity.

Materials and Methods: Thirty-five asymptomatic volunteers consented to participate. Six brands of off-the-shelf heel inserts were tested. Subjects walked along a ten metre walkway with no inserts and then with each pair of inserts, in a randomised order. The Pedar® in-shoe pressure system was used to record data. The five areas of interest were the heel, lateral three and medial two metatarsals, lateral three and medial two toes.

Results: The mean peak pressure (PP) under the heel was significantly reduced with inserts whereas PP recorded under the medial and lateral metatarsal heads was higher. With inserts, the contact time (CT) and pressure time integral (PTI) had increased under the medial toes, lateral and medial metatarsal heads; while under the heel, the CT had increased and PTI had decreased. The percentage roll over process of beginning of contact (BoC) showed a generalized decrease in the values under the metatarsal heads and medial toes with inserts. Although the general trend was a decrease in contact area (CA) with inserts, little difference was seen in the areas of interest among both feet.

Discussion: A comparable CA and increased PP, CT and PTI under the metatarsal heads and a decreased PP under the toes suggest that the metatarsal heads are prone to increased risk of injury while using inserts. This is complimented by the hastened BoC of the forefoot. The decreased PTI and PP under the heels can be attributed directly to the use of inserts.

Conclusion: The heel inserts should be used with caution inspite of their beneficial effects under the heel. The classification of these inserts as an “over-the-counter” product may need to be reviewed.