18/05/2021 at 5:23 pm #13865AnonymousInactive
I’m learning the ankle and have recently started looking at the calcaneocuboid ligament. We are looking at the anterior tubercle of the calcaneum and the calcaneocuboid component/arm of the bifurcate ligament (3 in attached image), however our sonographer worksheets state “dorsal calcaneocuboid ligament” which from my understanding is a separate ligament to this (4 in the attached image). Can these ligaments (dorsal calcaneocuboid and bifurcate ligaments) be distinguished on ultrasound or do they blend together?
19/05/2021 at 12:32 pm #13908Stephen BirdKeymaster
The way I think of it is that there is a bifurcate ligament. It has 2 components. The component I examine goes from the anterior tubercle of the calcaneum to the cuboid bone. The other component which I do not examine goes from the same location on the anterior tubercle of the calcaneum to the navicular.
As you can see both ligaments share a common origin which makes it a “V” shaped ligament hence “bifurcate”
When it fails it nearly always fails at the anterior tubercle of calcaneum origin and causes an avulsion fracture which bleeds like mad and causes the characteristic bruising and swelling.
I would simply amend your worksheet to say “calcaneo-cuboid ligament”
As long as you are looking at that anterior tubercle of the calcaneum carefully you are doing the right thing.
It is also important to understand that this ligament makes up part of the Chopart line of the foot which divides the hindfoot from the midfoot. If the AITFS survives inversion it really sets up a situation where the Chopart line is traumatized and the CC lig and the dorsal talonavicular ligaments fail.
The true dorsal calcaneo-cuboid ligament is slightly plantar to the bifurcate ligament and does not attach directly onto the anterior tubercle of the calcaneum but rather slightly plantar to this location.
I am certain you are correct in suggesting they blend together as after all they are just capsular ligaments in the calcaneo-cuboid joint so by definition they all blend together.
I think it is important to focus directly on the anterior tubercle of the calcaneum as this is where the pathology occurs and this location is just a bit anterior to the dorsal calcaneo-cuboid ligament.
I place the transducer parallel to the sole of the foot on the calcaneum, then I slide it towards the tows until I see the articulation between the calcaneum and the cuboid. Then I slide the transducer anterior (dorsally) and I observe the “step” between the calcaneum and the cuboid widen. Just before you lose visualization of the cuboid you see the calcaneo-cuboid component of the bifurcate ligament and this is where the injuries occur.
I have attached an image.
The red circle is the dorsal calcaneo-cuboid lig and this is rarely the site of injury.
The green circle is the calcaneo-cuboid component of the bifurcate lig and this fails at the proximal end.
The blue circle is the anterior tubercle of the calcaneum which fractures.
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