The Introduction here is largely from last week: For over 50 years, designing an orthosis off an impression around subtalar joint neutral and midtarsal joint max pronated position has made a stable orthosis. I have personally designed 20,000 pairs of these in 40 years, and know of their power and limitations. Yet, the cast or digital scan only captures the forefoot tilts present and the architecture of the foot. You still have to know where to set the heel. When I design an orthotic device, part of the estimation is learning which heels will do as you say, and which heels need alittle extra push. By this I mean, which feet typically respond to my Rx and which will need more Rx power.
With all patients, as I hear their complaints, and watch them walk and/or run, I am immediately designing the perfect orthosis in my mind. I categorize these patients by what correction I will need to achieve stability. These are A) need to achieve vertical (standard Root device), B) need to achieve less of an everted heel (discussed 2 weeks ago under "When to Varus Tilt?"), C) need to achieve markedly less everted heel, D) need to achieve an inverted heel position, E) need to achieve less of an inverted heel position (discussed last week under "When to valgus?"), and F) need to achieve markedly less inverted heel position (today's topic). Of course, the demands of the right foot may be totally different from the left foot.
Windswept Feet are a great example of how the demands between the right and left foot can be very different
I have defined my Gold Standard (Type A) orthosis as setting the Heel Vertical and any forefoot deformities balanced out. If you measure RSCP, this is typically accomplished in the range from 2 degrees inverted to 2 degrees everted. If you do not measure, the heel simply looks vertical to slightly off in either direction. This is called the Root Functional Orthotic Device or the Root Balanced Orthotic Device. This is how A is obtained to make a very stable orthotic device. Balance the heel to vertical and balance out all forefoot deformities (with casts or digital scans the lab can find the heel bisection, and set the heel bisection vertical to the ground easily).
Type F orthosis is for marked heel inversion correction.
Both this right and the right from the image above need more umph! in correcting the lateral instability caused by the varus deformity.
Type F is for extreme supinators, a very unstable foot. The common orthotic modifications used are:
- Lateral Kirby Skive (see Heel Skive under modifications)
- Setting the cast 2-3 degrees everted and holding intrinsically or extrinsically (see rear foot valgus extrinsic under modifications)
- Using 3-4 other anti-supination corrections: high lateral heel cup, lateral flange (see lateral flange under modifications), Denton modification (see lateral frame reinforcements under modifications), no rear foot motion applied, lateral forefoot extensions under 4/5 metatarsal specifically (this is a version of Dancer's Padding but not under 2/3 usually)
- Using 2-3 medial column weakeners: lower medial heel cup, lower medial arch, narrow medial width (see frame width under modifications), remove medial 1/2 rear foot post
