Hi, @Dymshyts, this is excellent research. I was going to comment on the problems with concepts that identify a diagnosis but then also include some causal event that the condition is referred to. The prior example you gave where you had diagnosis of X as a result of Y (ie: Nondisplaced transverse fracture of shaft of left tibia, subsequent encounter for closed fracture with nonunion Maps to 28012007 Closed fracture of shaft of tibia), the event being identified is X (the nondisplased transverse fracture), and it's from a prior closed fracture with nonunion (I'm assumign that's what 'subsequent encounter for... means).
I this case, I think it's an error to have a mapping to the fracture of tibia and a closed fracture, because the prior closed fracture happened in the past. Just record that there's a fracture of tibia.
However, if we can create our own hierarchy inside a snomed extention: I'd say that Nondisplaced transverse fracture of shaft of left tibia, subsequent encounter for closed fracture with nonunion falls somewhere below 'fracture of tibia' (something like fracture of tibia-> fracture of shaft of left tibia' but also you can find a concept under 'fractures resulting from closed fracture' -> fracture of shaft of left tibia, subsequent encounter for closed fracture', etc.
But, would this explode the concept hierarchy with all these possible multi-parent relationships and including all of these X due to Y concepts? But I do feel strong that X due to Y shoudln't result in both a record of X and Y on the same day, simply because we don't have the information that Y occurred simultaneously. I would expect somewhere else in the medical history you'd see Y as the primary event.
The main use case for putting these types of X because of Y in a hierarchy is that commonly you'd use the vocabulary to find things like 'skin blisters' but not 'skin blisters from burns' so you'd make a concept set expression saying 'give me skin blisters and descendants, excluding skin blisters from burns'