[Differences in plantar loading between orthosis with and without lateral wedge in healthy subjects]

Insoles and foot orthotics change the distribution of the plantar pressure. No information exists concerning the effects of plantar pressure distribution and lateral wedge orthoses. The purpose of this study was to determine the effect of the lateral wedge on the plantar pressure distribution.

The GP Mobil Data system was used to evaluate the data mentioned above, using a 6 mm lateral wedge orthotic worn by 50 healthy volunteers (100 feet). Patient age was 18 to 61 years. The first measurement was performed with, the second without a 6 mm lateral wedge. 50 volunteers walked a standardised distance of 10 m and the results with and without the wedge were compared. For evaluation, the foot was divided in 6 different anatomic regions. Statistical analysis was performed with the t2 test using graph pad prism.

The preliminary results revealed that the maximum peak pressure and intermediate pressure, contact time and force time integral decreased significantly at the medial middle- and forefoot plus the heel and increased significantly at the lateral middle- and forefoot using the lateral wedge. The maximum peak pressure under the great toe decreased by 22 % using a wedge, under the MTP I joint by 19 %, under the MTP II-III joints by 8 % and under the heel by 7 %. By contrast, maximum peak pressure increased under the area of MTP IV-V (+ 11.3 %) and under the lateral metatarsus (+ 15 %) when wearing a wedge.

This study reveals the effects of a lateral wedge orthosis on the plantar pressure distribution of the foot. These relationships and the changing pattern may serve as a useful guide for the clinician. A full medical screen of the foot should be undertaken before laterally wedged foot orthotic devices are prescribed.