Okay, so we know off the bat that this will be a past-participial phrase. This is because a past-participial phrase deals with an 'ed' at the end, meaning its context is in the past.
But what about the essential part? Well, look at the words used here. Essential means that if you were to remove a word, phrase, or clause, the passage would not make sense.
On the other hand, a non-essential means it would still make sense even removed.
A non-essential past-participial phrase has non-essential information which will usually be set off by a group of commas.
Do you think that the information given separated by commas is essential? Do we need to know it was broke in two places? Do we need to know it healed slowly?
Hopefully, this helps! =)
