Extrinsic Rearfoot Posting: Adding Stability with Birkocork

The following photos demonstrate the application of an extrinsic rear foot post. For many custom made orthotics, they are a vital component. For many Over The Counter devices like Superfeet, they can be added for greater stability. The Birkocork material is the same material used in Birkenstock sandals. It is heat moldable, and easily sanded. The material I purchase from JMS Plastics in New Jersey is bought 10mm thickness hard. It is heated in a convention oven at 475 deg F for 5 plus minutes until browning on top. 

Typical San Francisco Sunrise!!

Extrinsic Rearfoot Post after years of wear and no longer stable against the ground. The entire post should be on the ground flush for maximal stability.

Another view of how the worn down rear foot post is no longer stable and in full contact with the ground.

The original post is removed. The surface is glued with Barge cement as is the surface of the birkocork. It is let to dry for 10 minutes.

Then the birkocork is heated at 475 deg F for 5 plus minutes until the top starts to brown.

It is now laid on top of the heel area of the orthotic device.

Utilizing a glued hand, the birkocork is molded to the shape of the heel cup.

Then the birkocork is placed on the ground and the sides are pushed in to attempt a straight vertical wall around the heel cup. All excess will be ground later by a sander.

This demonstrates 2 rear posts with birkocork, one in its raw stage, and the other sanded. The bottom surface needs still to be sanded.

This demonstrates the complete extrinsic rear foot post ground to be in full contact with the supporting surface at the same time that the leading edge of the orthotic is in full contact with the ground.

Another view of the rear foot post flush with the ground as is the front or leading edge of the orthotic device. This is very stable. 

Another view of the complete sanded extrinsic rear foot post and a raw, not yet sanded, birkocork heel.