Foot Orthoses For Chronic Ankle Instability
In light of an increasing body of research on the
When the rearfoot is neither pronated nor supinated, and the forefoot has been locked against it, this relationship creates a neutrally positioned foot. Ideally in this position, a line bisecting the posterior aspect of the calcaneus will be vertical, and parallel to a line bisecting the lower third of the leg.
Neutral position is important because it is a position from which a joint will have the most efficiency. The neutral position of the foot is inherently different for each person, due to individual developmental variations.
Determining neutral position is important to maintain consistency and reliability with our measurements and treatments. Deviations from this position on an individual basis can cause compensations and abnormalities. Casting the foot in neutral position will capture the ideal angular relationship between the forefoot and rearfoot and a canvas on which to create an effective orthoses. Below you will find two methods for how to determine subtalar neutral position.
Note: the correcting capabilities of orthotic manufacturing CAD software is to a point where the capturing of subtalar neutral position is not completely necessary. Although we recommend casting in this position, there are cases and situations where a more natural position is preferable. As well, your expertise and experience in your field takes precedent when casting. Rest assured, your casts and scans will be carefully handled and your patients’ devices will be accurate and precisely designed.
Determining Subtalar Neutral Position
1st Method- Range of Motion
The subtalar joint has a rocking motion similar to a see-saw, when pronating and supinating the foot. It will swing through an arc, approximately one third of the motion is in the direction of pronation (eversion of the calcaneus) and approximately two thirds is in the direction of supination (inversion of the calcaneus).
Step 1- Roll the patients leg so that the foot in vertical (neither adducted nor abducted)
Sept 2- To locate the neutral position with the patient supine or sitting in a chair, grasp the foot with the thumb and forefinger at the 4th and 5th metatarsal heads. Slightly dorsiflex the foot on the leg and move the foot in an arc-like motion through supination and pronation. You will notice a “peak” at which the foot tends to fall off more easily to either side. At the top of this peak the foot is in neutral position.
Step 3- At this peak a minimal amount of dorsiflexion is required to lock the subtalar joint in neutral.
2nd Method- Palpating the Head of the Talus
Neutral position can also be determined by the congruency of the head of the talus.
Step 1 – Note the position of the navicular. It is a fixed bone, and is used as a landmark in locating neutral position. Also note the position of the head of the talus as it lines up with the navicular.
Step 2 – Note the relative position of the bones of the foot
Step 3 – The navicular, the talo-navicular joint, the head of the talus and the medial malleolus are in a line which goes dorsally and posteriorly
Step 4 – To find the head of the talus on the medial side, pronate the foot and locate the navicular with your thumb. Then move your thumb in a dorsal and posterior direction towards the medial malleolus. You will feel the protruding head of the talus.
Step 5 – Note where the lateral head of the talus is relative to the ankle joint. It is just off the center line of the leg and just below the ankle joint.
Step 6 – To locate the head of the talus on the lateral side of the foot, supinate the foot. This will make the head of the talus protrude laterally.
Step 7 – To locate neutral position: pronate the foot and palpate the head of the talus medially with your thumb. Then supinate the foot and palpate the head of the talus laterally with your index finger. Finally, rotate the foot so that you can no longer feel the head of the talus, either laterally or medially. When this occurs, the subtalar joint is in neutral position.
Note: in a low-arched foot, the head of the talus may protrude excessively on the medial side and not be palpable laterally. Conversely, in a high-arch foot, the head of the talus may protrude excessively on the lateral side and not be palpable medially.
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