Pertinent Principles On Rearfoot Posts And Corrections With Custom Orthoses

For most supinators, if they have a good everted forefoot deformity, I start with a standard vertical heel pour and proceed to consider high lateral heel cups, lateral phalanges and/or a Denton modification.

For extreme supinators (those with partial clubfoot, post-sprain lateral ankle instability or pes cavus with ligamentous laxity), I pour 5 degrees everted with the lateral Kirby skive. For these patients, this may be a starting point as one may have to try two to three orthoses to perfect the correction for their challenging foot.

For those with normal mechanics but pronatory symptoms (plantar fasciitis, medial shin splints, medial knee pain), I use the standard vertical pour to design a positive cast with the heel vertical and the forefoot deformities supported so they do cause the heel to be inverted or everted.

For mild pronators (those with 2 to 4 degrees everted from vertical or 2 to 4 degrees everted from neutral in rearfoot varus cases), I recommend 3 degrees inverted pour or 15 degrees with the inverted orthotic technique.1 For moderate pronators (those with 5-7 degrees everted from vertical or 5 to 7 degrees everted from neutral in rearfoot varus cases), I opt for 5 degrees inverted pour or 25 degrees with the inverted orthotic technique. For severe pronation (those with over 8 degrees of eversion from vertical or over 8 degrees from neutral in rearfoot varus cases), I recommend 7 degrees inverted pour or 35 degrees with the inverted orthotic technique.

Additionally, for these pronators, when using heel inversion in the cast (3,5 or 7 degrees or so), if you use a medial Kirby skive, you can typically lower the inversion by 2 degrees. This is equivalent for the inverted technique in which 25 degrees inversion is typically equal to a 15-degree inversion with the medial Kirby skive. It is a must to use high lateral heel cups (at least 21 mm) and lateral phalanges.

I do corrections with inverted or everted cast modifications and Kirby skives only. The rearfoot post is normally a zero-motion flat addition to the orthotic plate that holds the correction for the orthotic device. If you use a rearfoot post to correct 5 degrees, one has use a 5-degree forefoot post to keep that position.

Reference

1. Blake RL. Inverted functional orthosis. J Am Podiatr Med Assoc. 1986;76(5):275-276.

Editor’s note: This DPM Blog is an excerpt from the forthcoming Orthotics Q&A column, “Current Considerations With Heel Lifts, Top Covers And Rearfoot Posting,” in the June 2019 issue of Podiatry Today.