Fractures of the Distal Radius can and do occur in isolation, but an associated fracture of the Distal Ulna is very common, probably 99.0% involve the Ulnar Styloid, which can be displaced or non-displaced. The "Distal Ulna" anatomically includes the Ulnar Head (of which the Styloid Process is a part of the original Epiphysis) and Neck, which are the residual of the Distal Ulnar Epiphyseal growth in adults, and would be considered the Metaphysis. The Ulnar Neck is only a few millimeters in length. However, fractures can occur through this short segment. Even ICD-10 doesn't address the possibility of fractures of the Ulnar Head &/or Neck. Only the Ulnar Styloid is identified specifically (S52.61 _ _). Anything else (other than a Torus Fracture) goes into "Other" Fracture of the Distal Ulna, S52.69 _ _. The Distal Ulna just gets no respect.
As to your dilemma regarding the coding of open treatment of the Distal Ulna Fracture, but not the Ulnar Styloid, if the fracture is through the neck (+/- into the Head), you are right there is no procedural code. If the fracture is proximal to the Neck, it could be categorized as a Shaft Fracture and coded accordingly (25545). Otherwise you would almost have to go with an Unlisted Procedure (25999). Since a Plate and Screw fixation was used, you could equate/link it to the 25545 code for charge value.
I'll be interested to see what others offer to this query.
I hope this helps.
Respectfully submitted, Alan Pechacek, M.D.