Semantics

clavicle, collarbone
Когдђ Слђве бІло четІре гћда, ћн упђл со стџла и сломђл лљвую ключќцу. When Slava was four years old, he fell off a chair and broke his left clavicle (his collarbone).
collarbone
У негћ ключќцы торчђт. His collarbone sticks out.
This entry is concerned with the use of the word ключќца to refer to the collarbone in humans or animals, though the use of the term in referring to animals is rare. Common sense will dictate which of the expressions in this entry can or cannot be used to refer to animals or humans.

Note that the Russian plural form ключќцы can be translated with the English singular 'collarbone' or the plural 'clavicles'.