Photographer Rainer says, "Incapable of fast hunting and ambushing prey it has to be dependent on the pod which, one assumes, looks after it very well." The pod consists of five females and a large male.
http://www.dailymail.co.uk/news/article-2326868/Disabled-killer-whale-missing-fins-survives-help-family-hunt-food.html
David Kirby (author of 'Death at SeaWorld') has taken a look at WHY orcas may do this instead of choosing to abandon their disabled mates.
http://www.takepart.com/article/2013/05/19/killer-whales-take-care-their-own#.UZlb6mhIbxs.twitter
A permanently disabled orca known as Stumpy has been cared for by his pod mates for years - have a read of this article by Candace Calloway Whiting.
http://blog.seattlepi.com/candacewhiting/tag/stumpy-the-killer-whale/