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Friday, August 8, 2014

Inverted Orthotic Technique: Email Discussion

Dear Dr Blake,

I am a Bachelor of Podiatry student at the University of Newcastle in Australia. I am in my second last year of the degree and we are presently making your inverted devices.

I just have a question regarding one of the indications or criteria for your devices. In two lots of our notes it states 'NCSP of 8 degrees  or greater'. I don't understand why this would indicate a Blake inverted device, it doesn't seem to  fit with the other criteria. I was hoping you would be able to explain this particular point to me.

Regards,

Dr Blake's comment:

     Thank you so very much for your question. I am happy to answer all questions to this topic so dear to me. Fire away. We will have to look closely in our conversation at what is being said to make sure you and I are on the same page. The way I read what you are saying is that one of the instances of ordering a Blake Inverted Orthotic is if the NCSP (neutral heel position) is 8 degrees inverted or greater. And this is definitely one of the criteria, for it stands for a Highly Inverted Rearfoot Varus. With this foot type, using Root criteria and technique, you must now measure the RCSP (relaxed heel position) and see if it goes to vertical, pronates to the everted side, or stays inverted. When you attempt to control this foot with the Root Technique, you are just trying to stabilize even if the foot can be held near 3-4 inverted (close to neutral position). And it is hard to do this, with typically the foot is held close to vertical. If you think about the importance of neutrality, where the foot and ankle line up, you are actually no where close with the foot pretty pronated (even when inverted slightly). Problems can develop when the patient pronates farther than the device wants them to go. Say you want them to stay around 3 inverted. The patient has a 8 degree inverted NCSP, but the device is made around a pronated 3-4 degree inverted position (the highest inversion in Root Biomechanics). Typically being this far from neutral allows too much instability in the subtalar and midtarsal joints, and the foot can not be held at 3-4 degrees inverted (unless that is the end of the range). 

     In the same scenario, you are using the Blake Inverted Technique to not go from an everted position to vertical, but from vertical to an inverted position (same direction). A 40 Inverted Orthotic Device in a patient with a high degree of Rearfoot Varus, that really can not get to the everted side easily, typically holds the foot 8 degrees inverted (very close to neutral).  My starting point is 35 degrees Inverted, and for a new practitioner probably 25 degrees, but the positioning of these orthotics are so much better than Root since they hold the foot so much closer to neutral. 

     Okay, fire away with more questions now that I have confused you more. Rich

2 comments:

  1. Hi Dr Blake,
    I understand that the device allows us to reduce the midfoot pronation via rearfoot control. Hence, the angle is so aggressive. It will create a huge GRF to forefoot at forefoot loading. Should I use a full lenght device with extra cushion on it. And also, would the device have an impact to lateral calcaneus at heel strike?

    ReplyDelete
    Replies
    1. Carol, thanks for your comment. Why do you say it will produce a huge GRF at forefoot loading? At forefoot loading, 10% into the stance phase, the load should be on the heel and midfoot with this device, and minimized in the forefoot. Infact, as the patient goes into midstance, the forefoot load should continue to be less due to the greater midfoot support. The device creates its stability by controlling what happens after heel strike in general. Ideally, you want the device to grab the heel at heel strike and ease it into pronation with less pronatory velocity and total pronatory range of excursion. If the device is too corrected (not good), and heel strike is followed by contact phase supination, the lateral heel and foot will have excessive load. This is not desired. Hope this helps. Rich

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Thank you very much for leaving a comment. Due to my time restraints, some comments may not be answered.I will answer questions that I feel will help the community as a whole.. I can only answer medical questions in a general form. No specific answers can be given. Please consult a podiatrist, therapist, orthopedist, or sports medicine physician in your area for specific questions.