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Talar neck fractures

Why are talar neck fractures so prone to avascular necrosis?Talar fracture patterns

Sometimes a simple x-ray can say it all.  With all of the advanced testing that we have today, a simple x-ray can speak volumes.  You aren’t always able to capture the subtleties of bones and joints with each and every x-ray.  But every so often, you see a film that speaks to you.

The lateral foot x-ray in this post shows what is called the nutrient artery of the talus.  That small bullet shaped hole is the primary in-flow point for blood flow to the talus.  Why is that important?  Talar fractures typically happen through what is called the neck of the talus (the black line).  And that’s exactly where this image shows the nutrient artery.

Arterial in-flow of the talusMost bones have a redundant blood supply so that when a fracture occurs at one end of the bone, the opposite end of the bone is called into action to participate in healing.  But the talus is different.  Although it has a small amount of redundancy, such as arteries coming in from both the medial and lateral sides of the talar neck, the fault in that redundancy is that the in-flow into the talus is all within the neck of the talus.  Unfortunately, the neck of the talus is where the majority of fractures take place.  Therefore, even simple talar neck fractures are prone to loss of blood flow resulting in avascular necrosis.  The image to the left shows some of that vascular in-flow pattern.

The Hawkin’s classification of talar neck fractures

Talar fractures are described by the Hawkins classification.  In the Hawkins classification, all stage, 1-4, have the primary fracture line within the neck of the talus.  With increased force applied to the fracture, dislocation of the talus from adjacent bones becomes more complex, therefore increasing the risk of avascular necrosis. (1)

Hawkin’s classification and rates of avascular necrosis

Hawkins 1:   0- 13%
Hawkins 2:  20- 50%
Hawkins 3:  20-100%
Hawkins 4:  75-100%

What is avascular necrosis of the talus?

That little bullet hole in the first image says it all.  That one image captures the location of the nutrient, or most significant artery that supplies blood flow to the talus.  Avascular necrosis is the term used to describe loss of blood flow to bone.  If the bone, and in the case, the talus, looses blood supply, the bone dies and collapses.  The only solution is a pantalar fusion, fusing the heel bone (calcaneus) to the leg bone (the tibia).

In my book, that’s a bad day.

References

http://www.wheelessonline.com/ortho/fractures_of_the_talar_neck

Jeff

Dr. Jeffrey Oster
Jeffrey A. Oster, DPM

Medical Director
Myfootshop.com

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Updated 1/3/2019

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Comments
5/6/2018 5:10 PM
Hello Dr. Oster, It's been about 12 years since my Hawkins 4, talus neck fracture. I miss your old blogs, they really helped me to heal and gave me a good solid source of information. As for me, I am very limited on my range of motion but I can walk without any sign of limitation. I do suffer from nerve damage and just recently had a MRI on the ankle and there is small spot of AVN in the middle of the talus and a small spot on the dome. I had all the screws removed due to the head of the K-screws catching on my ligaments but there is still some metal particles in the talus. i feel that I am very lucky to have a great Surgeon (Dr. F. Moll) in Sunrise, Florida and still feel that the hyperbaric oxygen therapy was the key. Thanks, Henry B.
5/6/2018 8:48 PM
Henry, I certainly remember your story. Hawkins stage 4 is not a pretty thing. Glad to hear all is well, or as well as could be expected. I had to shut down the old discussion forum because my state medical board could not give me a clear decision as to whether the discussion forum was or was not the practice of medicine. Also, I had every blogger's dream come true in that I had a couple of self appointed moderators. But when you're dealing in medicine, that's a bit of an awkward position. Great to hear from you. Jeff