This is part 12 of a series that should be read in order.
Key Points:
- What is a Medial Lateral Instability Patient?
- For an M orthosis, do you consider when Rx writing the supination correction first or second?
- What are parallelogram feet?
- Why treat feet asymmetrical if they exhibit different tendencies?
The Medial/Lateral Instability Orthosis
Medial Lateral Instability patients are a subgroup of over pronators. These are patients that pronate (medial instability), yet also have some supination tendencies (lateral instability). Dr. Mark Warford gave a great example of this when there is pronation on one foot and supination on the other foot. He calls this situation parallelogram feet. Dr Louis DeCaro talks about making sure you look at each foot separately in a patient because one side can be a different type than the other side. We know that a patient can walk and run or bike with differing mechanics and need different orthoses for different functions. However, here I am talking about patients who, within the same foot, have tendencies of pronation and supination combined and how I approach these feet. We know that pronators can be big supinators in the wrong shoe, or the wrong shoe/orthotic combination, or the wrong orthotic prescription for them. I started looking at, and adjusting treatment for, my patients in the 1980’s when the rules around the Inverted Orthotic Technique weren’t solid yet. Many of the pronators became supinators with slight overcorrection of the orthoses. I had to know how to deal with these cases. The pronation of a patient tends to be assessed both statically and dynamically, and the supination of a patient largely only dynamically (meaning it can be hard to measure anything, although you can get good at predicting these patients by certain measurements).
So, basically you are observing a pronator and deciding how to write your Rx based on the pronation first. Here the static measurements are for the pronation correction, and then we back down the pronation ideal control, and add lateral support. This is why a pronator with chronic inversion ankle sprains can be better off with some modified version of the Inverted Orthotic Technique (yet another counter-intuitive concept). We can avoid overcorrection of pronation with this type of device.
Over correction of pronation means that a pronator with an orthotic device will then function with some lateral instability and its related problems. I see more overcorrection with orthotic devices in traditional Root devices without good lateral column support, and typically forefoot varus support with overly high medial arches. I also see over correction when a patient with an orthosis is just placed in an unstable shoe. And, finally, I see overcorrection when the lateral instability tendencies were not caught initially by the prescribing doctor (or me), so lateral protection (M device) was not part of the original orthotic design. So, this patient gets a Modified P orthosis.
The types of devices here are the same for our pronation patients. So, BML is really BP with less pronation control and more supination control. ML1 is the same as P1 with less pronation control and more supination control. This is the same for ML2, ML3, ML4, ML5, and ML6. Decide how you want to deal with the pronation of the patient first, then slightly lessen that correction while increasing supinatory control. More on this exciting topic next week.
Review of all the Orthotic Types Being Presented
Corrective Orthotic Devices
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- Balancing (B): (B1 and B2)
- Pronators (P): BP, P1, P2, P3, P4, P5, and P6
- Supinators (S): BS, S1, S2, S3
- M/L Instability (M): BML, ML1, ML2, ML3, ML4, ML5, and ML6
- Shock Absorption (C): BC, C1/C2, C3/C4/C5, C6, and C7
- Sagittal Plane (H): BH, H1, H2, and H3
These 2 pronators can become laterally unstable with poor shoe gear selection, overly corrected orthotic devices, weak peroneals, loose lateral ankle ligaments, etc. In these cases, many need an M orthosis, and not a P orthosis.
