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Oct 20

Written by: Cherri Choate, DPM
10/20/2010

The development of hallux abducto valgus and hallux rigidus is dependent on the motion and position of the 1st ray.  The abnormal position of the 1st ray impacts the motion of the 1st MPJ.  Presently, the working theory is that as the position of the 1st ray becomes more dorsiflexed, the motion of the 1st MPJ becomes more limited. So what can lead to this abnormally dorsiflexed 1st ray position?  A multitude of issues can lead to a dorsiflexed 1st ray, including structural, functional and compensatory pathology. One of these issues, the role of the plantar fascia in 1st MPJ motion, has been explored in recent years.  Research has established that increased strain in the plantar fascia leads to less motion at the 1st MPJ.  In fact, two clinical examinations,  the Hick's test and the Hupscher maneuver, are now common components of both the lower extremity biomed evaluation, as well as the bunion evalution.  

Since research has established this relationship between the plantar fascia and the 1st ray complex, how do we apply this knowledge to an orthotic prescription? The answer to that currently lies in study by Kogler regarding plantar fascial strain.  He studied the effect of a variety of forefoot and rearfoot wedging combinations on plantar fascial strain. His study established that the wedging combination that led to the least amount of strain in the plantar fascia was the forefoot valgus wedge. Application of this finding to orthotic prescription writing can be accomplished by two direct choices:  forefoot valgus wedge or reverse Morton's extension. By adding either of these forefoot extensions to an orthotic, the plantar fascia undergo less strain, leading to more normal range of motion of the 1st ray and subsequently more normal range of motion at the 1st MPJ.

The addition of the reverse Morton's extension is likely better tolerated than a valgus wedge, but the principle is the same.  This is just one option to consider when fabricating functional orthoses for patients with 1st ray and 1st MPJ pathology.

For more information on the study by Kogler, take a look at today's EJournal entry.  




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