Secrets To Fabricating Effective Custom Orthotics

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How To Prevent Heel Irritation When Using A Medial Heel Skive

The medial heel skive is an effective technique for providing greater control in an orthoses. It incorporates an interior varus wedge into the medial aspect of the heel cup of the orthosis. In order for this to be effective, the heel cup must be high enough to apply force medial to the subtalar joint axis.

As this technique becomes more popular, it becomes increasingly important to understand how to prescribe properly. Keep in mind that medial heel skive can lead to heel irritation at the edge of the orthosis in two instances: when the heel cup is too narrow and when the heel cup is too shallow.

Since the medial heel skive puts greater pressure on the heel fat pad, it widens the heel fat pad. Using a deeper heel cup can help contain the heel fat pad and prevent lateral edge irritation. Also make sure you provide caliper measurements of the heel width on weightbearing to your lab in order to ensure proper width in the orthoses.

Since a medial skive shifts the foot laterally, the heel cup must be deep enough to contain the heel and provide control without causing edge irritation. The minimum heel cup depth when using a medial heel skive is 14 mm. The heel cup depth should increase as the amount of skive increases. Therefore, you cannot use a medial skive with a dress orthoses since the heel cup depth is generally less than 14 mm.

When you are combining a medial skive with inversion, the slope you create can cause the foot to slide into the upper lateral edge of the heel cup. Using a deeper heel cup will prevent this problem. To avoid lateral heel cup edge irritation, use a 20-mm or 22-mm heel cup when the amount of skive plus the amount of inversion is greater than 5. To give you an example, 4mm skive plus two degrees of inversion = 6. Therefore, you would prescribe a 22-mm heel cup.

Direct milled polypropylene (as seen above) and vacuum formed polypropylene are “the most effective and versatile materials for functional orthoses for athletes,” notes Larry Huppin, DPM.
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Author(s): 
Guest Clinical Editor: Nicholas Romansky, DPM

There is no shortage of issues to consider when you are prescribing custom orthotics for different types of patients, whether it’s knowing what to look for during the biomechanical exam or understanding the keys to proper casting. With these things in mind, our expert panelists explore various issues from prescribing orthotics for athletes to altering orthotics in case of improper fit.

Q: What keys do you look for in your biomechanical exam?
A:
Patrick Nunan, DPM, starts his biomechanical exam by having the patient sit on an exam table while he evaluates the joints’ range of motion, muscle strength, limb length, forefoot to rearfoot and rearfoot to leg. When the patient is standing, Dr. Nunan examines his or her calcaneal position, tibial varum, abduction of the forefoot and neutral subtalar joint position. He also observes front, rear and side views of the patient walking or running. Dr. Nunan says he will schedule an F-Scan evaluation if he has concerns that go beyond the initial exam.
In addition to observing patients while they are in sitting, standing and prone positions, Nicholas Romansky, DPM, says he listens to his patients’ observations. He checks out the patient’s type and wear of sneaker or shoe, and also suggests looking at any old orthotics the patient may have worn.
Whether you or an assistant cast the orthotic, he advises you to examine the finished cast and make sure the cast captures what you want it to capture.

While Larry Huppin, DPM, performs a complete biomechanical examination on each patient, he says the exam tends to be focused on the patient’s presenting pathology. For example, when a patient presents with functional hallux limitus, Dr. Huppin says you will usually note excessive ground reactive force (GRF) under the medial column. The increased GRF prevents the first ray from plantarflexing during propulsion, which leads to increased compression in the first MPJ.
In that case, the primary focus of Dr. Huppin’s biomechanical exam is to determine the cause of the increased GRF. He examines the location of the axis of the subtalar joint and calcaneal eversion to see if rearfoot eversion is the cause. He proceeds to evaluate the first ray position and the forefoot-to-rearfoot relationship in order to determine whether a plantarflexed first ray or an everted forefoot position is leading to the increased force.
“Our biomechanical evaluation is not focused on determining specific degrees of angulations, but rather on identifying pathological forces so that we can prescribe an orthosis to mitigate those forces,” says Dr. Huppin.

Q: What are your key parameters when fabricating custom orthotic devices?
A:
Dr. Nunan first considers if a custom orthotic will improve his patients’ symptoms or if he needs to address other factors like the patient’s shoes, muscle imbalance, training, intensity and surface.
When you decide that a custom orthotic can be helpful for the patient, Drs. Nunan and Romansky say it’s important to tailor the prescription to address the patient’s symptoms. Dr. Romansky notes DPMs and other health professionals sometimes will fabricate the same type of orthotic routinely regardless of their problem. Basically, all patients would get the same type of orthotic, which he says should not happen.
“Pick soft goods/materials appropriately,” emphasizes Dr. Romansky. “These are just as important as the plate material.”
Drs. Nunan and Romansky say custom orthotics should also address the needs of each patient’s level of activity and activity type. Dr. Nunan also takes the patient’s body weight, biomechanics and foot type into account and looks at the patient’s shoes.
Dr. Huppin bases the orthotic prescription on the patient’s presenting pathology and etiology. When a patient has first MPJ pain due to functional hallux limitus, Dr. Huppin says you want to decrease compression within the first MPJ. If the pain is due to an everted heel, Dr. Huppin might employ a deep heel cup and a medial skive. For an everted forefoot, he says a reverse Morton’s extension may be appropriate.

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