Do you know of a term used to describe this finding?
There are a few - the process is known as osteochondosis (with an unclear aetiology), but is also recognised by the eponymous term "Freiberg infraction" or Freiberg disease.
Is anything else in your differential?
This can be seen as a normal variant, although is quite advanced for that. Plus the patient is symptomatic (pain, difficulty weight-bearing). With an acute history, close examination for a fracture is important, but there is no acute cortical break on these plain studies.
Flattening of the third metatarsal head consistent with early osteochondrosis/Freiberg infraction. Preserved MTPJ. No fragmentation.
No acute fracture.