The Fettig modification or technique is a modification of the inverted foot orthotic technique when a forefoot valgus is present to support the lateral column. The original inverted foot orthotic technique ignored the forefoot to rearfoot relationship in preparing the positive model. The technique balances a forefoot valgus deformity laterally in the negative model modifications for the foot orthotic. It was given this name by Richard Blake, DPM after Mathias Fettig, DPM who showed him the modification of the inverted technique. Blake suggested in his book that 25% of his own inverted orthotic designs used the Fettig modification.
Hypothetical Example of the Fettig Technique:
A negative model of the foot measured 8 degrees of forefoot valgus and the clinician wants the equivalent of 30 degrees of rearfoot inversion using the inverted orthotic technique. Using the traditional plaster positive modelling technique a nail will be put in the area of the first metatarsal head to invert the cast 38 degrees to give the 30 degrees needed (becasue of the 8 degrees of forefoot valgus). Using the Fettig modification another nail will be placed in the area of the fifth metatarsal head to bring the forefoot back 8 degrees. The heads of the nails are then used to create that anterior platform of plaster as part of the positive plaster model for the molding of the foot orthotic shell, giving the 30 degrees equivalent inversion in the rearfoot and the lateral column will be elevated to accommodate the 8 degrees of forefoot valgus. The finished foot orthotic would be a 30 degree inverted foot orthotic with a 8 degree Fettig Modification.
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