Top 100 Biomechanical Guidelines #32: Stress Fractures and Joint Arthralgia treated with Increase Shock Absorption

     Shock Absorption is needed following the impact (collision) of the foot against the ground. The shock wave that radiates up the leg is approximately equal to your body weight with normal walking, increases as you increase speed or go downhill, and can measure 2 to 5 times body weight with normal running. It is this shock wave that needs to be reduced to help many avoid injury by changes in shoegear, changes in surface, changes in shoe inserts, and custom made shoe devices. The King of all is the Hannaford Device. Hundreds of my patients have benefitted over the last 25 years, and I am hopeful to spread the word on how it is made.

     Hannaford Orthotic Devices, developed by Dr David Hannaford while practicing podiatry in Eugene, Oregon, are 2 layers of 1/2" plastazote material vacuum pressed around a mold, and then ground into shape to fit a typical athletic shoe. The layer of plastazote material against the skin is memory foam, soft in nature. The second layer of material is white plastazote, firmer and more durable in nature.

Impression Casts are used to make a Hannaford Device.

The 2 sheets of plastazote are cut with the memory foam full length and the white, more durable, plastazote cut to sulcus length (just behind the toes).

The length of the soft plastazote is approximately 1 and 1/2" longer than the foot and will be trimmed after the molding to fit better.

This is how the 2 pieces will be pressed with the softer memory foam against the foot.

Before vacuum pressing, both pieces are glued with Barge Cement so they will become like one after the press.

Before pressing, the toe area of the mold is covered with a soft material to flatten this part of the press. Without this, the memory foam molds around the toes too much. You need the orthotic to end up longer than the original foot.

The 2 pieces are placed in the convention oven heated at 475 deg F. Because the white layer heats up slower than the pink layer, the white layer is placed down on the surface.

Within the convention oven, the plastazote material is checked every 20 seconds and removed when the toe area begins to brown. A spatula is used to remove, but it can be handled gently with your hands.

Here it is centered over the mold with overlap around both sides and front and heel. You need to get as far forward in the press as possible for the best press. See the memory foam layer is being placed against the foot.

Once the press is started, you need to push down from the sides to help the vacuum remove all the air. The press is normally done in 20 minutes/foot.

After the press, wrap the mold with plastic wrap tightly for 1 hour to let the material cool completely in the shape of the mold.

Once removed from the wrap, mark the front length approximately 1 and 1/2" from the end of the mold, and mark the sides the exact width of the foot. Since I have a video of the grind, I will let that finish this post off.