Is this the same as a 'pulled elbow' / 'nursemaid elbow'?
No. A pulled elbow is a subluxation of the radial head and usually easily / spontaneously reduces.
If a fracture of the ulnar was present, what would this be known as? Is this common?
Moteggia fracture dislocation. Yes, more common than an isolated radial head fracture.
What is the order of ossification of the elbow? Is this patient appropriately aged?
The order can best be remembered using the mnemonic CRITOE: capitellum (1 year); radial head (5 years); internal (medial) epicondyle (7 years); trochlea (10 years); olecranon (10 years); external (lateral) epicondyle (11 years). Yes, this patient is appropriately developed.
Two views of the elbow demonstrate an anteriorly dislocated radial head. No fracture identified.