USN does not distinguish between generic health-care activities and (formalized) health-care procedures. In fact, the Metathesaurus assigns 6787 CUIs to HCA with
no assignment to a procedure! This is a good guide to the splitting. Therefore, here medical procedures are not children of health-care activity defined in theory:clin-act, but of procedure.
(=> (Medical-Procedure ?Self) (Exists (?A) (And (Temporal-Part ?Self ?A) (Health-Care-Activity ?A))))