Key Insights On Orthotic Casting And Function
Our expert panelists discuss the pre-casting workup for orthotics, the advantages of plaster casting and the importance of checking range of motion. They also offer pointers on what you should look for before sending casts to the lab and troubleshooting when patients say their orthotics are not working correctly.
What biomechanical assessments optimize a pre-casting workup for functional orthosis?
Denise Freeman, DPM, details the most common assessments she performs before writing an orthosis prescription.
Forefoot to rearfoot angular relationship. This allows her to diagnose an inverted or an everted forefoot deformity. This assessment also facilitates a decision about the amount and degree of forefoot posting, according to Dr. Freeman. She also checks this later when evaluating the negative cast.
Neutral calcaneal stance position (NCSP). This measurement permits her to diagnose a rearfoot deformity such as rearfoot varus or valgus.
Relaxed or resting calcaneal stance position (RCSP). As Dr. Freeman says, the RCSP reveals if the foot has had to pronate or supinate to compensate for any deformities in the kinetic chain. She calls the RCSP a useful measurement when deciding how much medical skive she will incorporate into the orthosis shell.
First metatarsophalangeal joint (MPJ) range of motion. Dr. Freeman advises measuring this in both NCSP and RCSP. She says it is useful when deciding whether to add a reverse Morton’s forefoot extension.
Limb length. Although she does not routinely assess limb length on every patient, Dr. Freeman says it is an important and often overlooked measurement. She will frequently add her own heel lifts onto the orthosis as doing so allows her to titrate the height.
Joe DeRose, DPM, emphasizes observation of gait and stance prior to non-weightbearing exams. While the biomechanical exam should be thorough and efficient, Dr. DeRose will focus the exam on things that will change the prescription. For example, if he observes an inverted appearance in RCSP, this may lead to examining the forefoot more carefully. If there is a rigid everted deformity of the forefoot, he says one can prescribe a valgus wedge or reverse Morton’s extension.
Dr. DeRose emphasizes a strong focus on the pathology, including the presenting complaint, deformities such as hallux abductovalgus and leg length discrepancies, and abnormalities in stance and gait. He says this focus allows for better prescription writing and eliminates unnecessary non-weightbearing exams.
Jay Cocheba, DPM, examines subtalar joint range of motion in the frontal plane, looking for both the total range and end range of motion in either direction. As he notes, ascertaining the total range helps identify lapses in symmetry and the amount of correction the patient may tolerate in the heel cup. The end range suggests the amount of rearfoot correction necessary so he can decide on details of that correction, such as posting, shell depth and adjuncts such as skives. At the same time, Dr. Cocheba looks for the amount of arch deformation between NCSP and RCSP, which aids his decision on how much arch fill to add and ideal plate stiffness.
Why is it important to check ankle range of motion?
All three panelists note that one may need a heel lift to accommodate range of motion. Dr. Cocheba often prefers the heel lift to be easily adjustable if he expects an improvement from surgery, physical therapy or a home exercise program.
In addition to adding a small heel lift to accommodate range of motion, Dr. Freeman says one may use a stretching program to normalize ankle function before dispensing the orthosis.