Considering the Height Compensation

If a height compensation is required, it can be realised, for example, through the orthosis. A height compensation at the orthosis provides the advantage that patients may wear ready-made shoes. The following text describes which steps must be considered when modifying a height compensation, in addition to the steps of the usual modifying technique. One part of the modifying technique is, for example, Making the Negative Cast with e-Cast, where you can find all information regarding the positioning of the plumb line - which is also used in this tutorial - under the subitem “Determining the Ideal Position”.
And, if the final model is finished, you can see how to proceed with a height compensation when producing an orthosis by using the online tutorial Producing a Height Compensation.

Considering the Height Compensation

Step 1/9

When producing a height compensation, it is essential to create a leverage ratio that is similar to the contralateral side. To do so, the following steps are necessary:

  • compensate the volume under the heel and in the forefoot area (blue hatching),
  • set the heel back (pink hatching),
  • define the mechanical rolling-off line (j),
  • consider the heel-to-toe drop (x),
  • consider the toe spring (y).

Note: Mark the plumb and rolling-off line of the healthy/unaffected foot on the shoe’s insole (or a copy) and use the insole as a guidance for all further steps

Step 2/9

Setting the Ideal Position
You can set the height of the pitch and the height compensation on the h-Cast. On the contralateral sight, the patient may wear an orthosis or also stand on an h-Cast. If possible, the patient stands in the gait-related normal posture. Here, the stance-related normal posture is described:

  • feet as close as possible,
  • consider the external rotation,
  • both legs carry the same load,
  • drop the plumb line,
  • put the h-Cast back until the plumb line drops correctly and a balanced load on both legs is possible.

Also consider the online tutorial Making the Negative Cast with e-Cast.

Step 3/9

Modifying the Positive Cast

  1. position the aluminium clasp or similar
  2. Prolong the forefoot up to k. k stands for the inner shoe dimension and j marks the mechanical rolling-off line.
  3. fill the form with plaster
  4. create a smooth transition
  5. let the model harden

Also consider the online tutorial Making the Positive Cast and Modifying the Positive Cast KAFO.

Step 4/9

In order to define the toe spring, determine the trochanter (B) first. Tie a string to a pen. The string’s length (R) should match the distance from the trochanter (B) to the rolling-off line (C) (R B - C).
Hold the string at the trochanter (B) and place the pen at the rolling-off line (C). Use the pen to draw the circle line on the positive cast.

Step 5/9

Modify the forefoot area of the foot piece corresponding to the drawn marking.
Note: Modify the bottom and the top of the foot piece parallel to one another. This way, the screw clamp can easily be attached in the later work steps.

Step 6/9

Mind the parallelism when modifying the foot piece. Modify the heel, the rolling-off area and the forefoot area parallel to the axis/axes.

Step 7/9

Modified positive cast from below:

  • j is the mechanical rolling-off line
  • k is the point where the aluminium clasp had been positioned
  • l is the inner shoe length (the heel protrudes; pink hatching)

Step 8/9

Modified positive cast from lateral:

  • j is the mechanical rolling-off line
  • k is the point where the aluminium clasp had been positioned
  • l is the inner shoe length (the heel protrudes; pink hatching)

Step 9/9

Modified positive cast from lateral while standing:

  • the toe spring y must be modified
  • it begins at the mechanical rolling-off line j

The toe spring is essential for:

  • the foot piece’s fitting in the shoe
  • making a physiological terminal stance possible → knee remains extended longer → body's centre of gravity remains at one height → energy is saved
  • making a physiological swing phase possible → functional shortening of the leg → swinging freely without compensating (e.g. vaulting, circumduction) possible → energy is saved

Last Update: 7 September 2020

 


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