Hi Diane,
Indeed all things that are echogenic are not necessarily calcification.
Yes indeed delimitation means the same as a longitudinal split tear of the tendon and when this occurs you often get that classic linear line of scar tissue.
I don’t think I can be perfect in always allocating the correct diagnosis to an echogenic area in a tendon. Most times I have no difficulty but there are always occasions where I sit on the fence.
With a classic small enthesis based intrasubstance tear with a linear delimitation component that has granulated I am looking for a small peck in the enthesis at the doort of an echogenic line that runs along the longitudinal axis of the tendon fibres. The line is typically thin and not densely shadowing as it represents granulation tissue. Also it is not tender on sono-palpation
Hydroxyapatite deposition is a bone salt migration from the bone to the tendon and hence it must originate at the enthesis where tenocytes and osteocytes are side by side. Hydroxyapatite is more cloud like (cumulous) in nature and less sharp and linear. In the acute stage it is not particularly attentive and may even be seen to move like a liquid with Tx pressure. It is very tender on sonopalpation and it is much bulkier that a linear granulation. When it matures it may simply become a hard dehydrated rock of calcium with dense acoustic shadowing and is typically not tender at this stage.
Dystrophic calcification is any calcification that occurs in a tendon due to a tear that is scarring up or an area of tenocyte exhaustion that has calcified. Dystrophic calcifications are within the tendon matrix and don’t need to have a relationship to the enthesis like a delimitation tear or hydroxyapatite. You see dystrophic calcification commonly in the distal patella tendon and the Achilles tendon as a result of tenocyte exhaustion and dystrophic calcification deposition. These calcifications often produce an acoustic shadow.
So as you can see there is some overlap in my mind but as general rule I think I can tell these entities apart.
The plain radiograph will also give some valuable clues.
Steve