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Thursday, January 23, 2014

Thursday's Orthotic Discussion of the Week: Fettig Technique

The Fettig Technique is a specific modification of the Inverted Orthotic Technique designed by Dr Mathias Fettig while practicing in Montana. The classic Inverted Technique ignores the forefoot to rearfoot relationship in preparing the positive cast. Dr Fettig felt for his patients with forefoot valgus/plantarflexed first rays, where he wanted the correction of that everted forefoot deformity, but also wanted the heel inversion, he could combine the 2 techniques. And they have worked well together stabilizing the forefoot and rearfoot components.


All positive casts are poured vertical heel as a reference point no matter what correction you are going to do to the cast. 

Here is an example of a left foot cast that once poured vertical heel so that the top of the cast was parallel with the floor, the cast captured 6 degrees of everted forefoot deformity (inverting the top of the cast 6 degrees).

The front of the cast needs to enclose the first and fifth metatarsals in making what is called the Anterior Platform. 

The first and fifth metatarsals should be marked at their lowest points to the ground, and then a border 10-15 mm proximal to that point marked for the edge of the Anterior Platform. This is due to the need for the plastic to end behind (towards the arch) the weight bearing surface. The 10 to 15 mm leeway is an estimate with longer feet needing more and shorter feet less leeway or clearance. 

Here is a bottom view of the foot with the lines initially drawn between the first and 2nd metatarsals and then the 4th and 5th metatarsals. The low point on the first metatarsal is relatively easy to find with the line towards the arch dropped down the side of the foot and 10-15 mm from that low point. Unless visualization of the 5th metatarsal is obvious, I love to leave this line even with the first metatarsal line. This makes a square and stable leading edge of the orthotic device. 

Here the line for the 5th metatarsal is dropped down. 

Now the fun begins. This image is of the 2 nails needed for the Fettig Modification of the Inverted Orthotic Technique. If the FF Valgus measurement is 6 degrees taken from the top of the cast seen in an earlier image, and 20 degree Inverted Orthotic Technique is necessary for pronation control, then the initial medial nail sets the cast at 26 degrees inverted. The second nail in the fifth metatarsal head then sets the total inversion back to 20 degrees. In essence, we have accomplished a 20 degree Inverted Orthotic with a 6 degree Fettig Modification. 

Once the nails are in place, the plaster to make the Anterior Platform is mixed. I always have 2-3 plaster bowls working, each with different consistencies waiting for one to be the perfect blend of solidity and liquidity to be ready to be used. You can see by this photo that I use color dyes. Also floating in the basin in the back are pieces of wood that I will use to make the anterior platform. These will be placed into the anterior platform under the first metatarsal head, and need to be super saturated with water so not brittle (more the consistency of the plaster). 

You can see from the above image that the wooden sticks (parts of wooden tongue blades) are saturated with water before utilizing. They are places into the anterior platform after making and before the plaster dries. Only a small part will be used that goes into the medial arch fill. This is important when pressing with high power presses to avoid breakage of the platform from the medial arch. 

You need to be patient with the plaster as it dries to a certain consistency before making the Anterior Platform. 

Here the plaster is stirred every 2 minutes or so checking on its' consistency. 

Once the plaster is ready, moldable but not runny, it is placed on a small piece of paper.

The positive mold is now placed on the paper in the area of the anterior platform. You place the positive mold with the nails down gently trying not to distort the nails. 

Here, my brother Bob, who is wonderful at designing these molds, works the plaster so that the sides are smoothed. 

Bob is cutting away excess plaster and making the side walls straight on the lateral side and slightly bevelled outward on the medial or arch side. 

The Anterior Platform is applied and the wooden stick to prevent breakage inserted. 

I wanted to show that mistakes are made. I am trying to set this Fettig at 20 Degrees but the placement of the plaster on the mold was checked at 24 degrees. Oh well, do it again!!!!

New plaster applied to make another Platform. 

Measurement shows a perfect 20 degrees. 

The Anterior Platform is roughly squared on all 4 sides.

If you are skilled at orthotic making, you can tell a 6 degree Forefoot Valgus correction (lateral side) and a 20 degree overall inversion have been designed into this Anterior Platform.

Another image of the Fettig Modification capturing all 6 degrees of Forefoot Valgus within the 20 degree Inverted Orthotic Technique. The wooden stick will be cut about 1 and 1/2 inches from the plaster.

The finished positive cast capturing a 6 degree Forefoot Valgus deformity and 20 degree Inverted Technique with the medial and lateral expansions left foot.

Same for the right foot.

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Thank you very much for leaving a comment. Due to my time restraints, some comments may not be answered.I will answer questions that I feel will help the community as a whole.. I can only answer medical questions in a general form. No specific answers can be given. Please consult a podiatrist, therapist, orthopedist, or sports medicine physician in your area for specific questions.