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Sunday, September 23, 2012

Pre-Operative Discussion Prior to Resurgery to a Ankle Fusion Complication

The following photos are on a patient who had a severe complication post ankle fusion where the foot was left inverted to the ground. Slowly over the last 8 years the foot has become more "C" shaped with marked weight bearing along the lateral side of her foot, and little to no weight bearing medially (big toe side). She is presently speaking with 3 surgeons and deciding on the most corrective surgery to re-center her heel and get her stable on the lateral side of her foot (4th and 5th metatarsals).

After a line was drawn to bisect the heel while the patient lied prone (on stomach), the patient was asked to stand up in her normal stance of gait. The paper post its form a straight vertical line next the heel bisection to demonstrate the inverted position of the heel. Careful measurement reveals that this line is 5 degrees inverted. Root Biomechanics states that any inversion of the heel over 3-4 degrees will cause lateral instability and the problems associated. 

Here the photo shows the gross asymmetry of the body with the left heel everted (pronated) and the right heel inverted (or supinated). The body seeks symmetry in function, so this poor biomechanical position forces the body to attempt compensation. In this patient's case, the compensation has lead to gradual foot, ankle, knee, hip and low back symptoms. As a podiatrist, since the right ankle is fused in this position, and the subtalar joint is rigid and arthritic, I can not change that position. If the surgery can straighten that heel position, and I suggest even erring on shooting for  2-3 degrees everted, I know I will be able to center the left side with orthotic devices.

This photo focuses on the lateral weight bearing on the fifth metatarsal base. This is extreme pressure which produces many symptoms, and I have probably attempted 8 or so different orthotic versions to attempt to help. Some have been at least somewhat helpful. In another situation, if the ankle was not fused, I could generate force with the orthotic device to evert the heel lessening the force on the lateral midfoot. 

This photo emphasizes the normal straight lateral border, instead of the C shaped unstable border of the right inverted foot. The surgeons must decide during surgery if the only surgery necessary is to straighten the heel (possibly with a subtalar joint fusion), or if more than that is necessary (ie triple arthrodesis, lateral column shortening, soft tissue releases, etc). 

I apologize for the orientation of this photo. What I attempted to show is that the fifth metatarsal head on the  right foot was 1 inch medial to the lateral malleolus when the foot was maximally pronated, and is normally 1-2 inches or more lateral to the lateral malleolus. This can be a reliable landmark in surgery to decide if the surgery will do what it was intended to do. So the 5th metatarsal is at least 2 inches too far medial.

Here, on the left side, the fifth metatarsal head is 1 and 1/2 inches lateral to the 5th metatarsal head when the foot is maximally pronated. This is a more normal relationship and ensues good even weight bearing of the entire foot.

Here is the patient is in shoes and orthotics to attempt to correct the heel positioning. You can see that the right foot is still inverted and the left easily centered. 

1 comment:

  1. While one may, to some degree, be trading one set of troubles for another, wouldn't a below the knee amputation with a high end prosthesis be far more functional than a fused ankle? In similar circumstances I might strongly consider that option. People run marathons and climb mountains on good prosthetics.


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.