Historically, surgeons had to make large incisions in the skin and split and move the deltoid muscles to gain access to the rotator cuff. Serious and debilitating complications developed if the deltoid muscle origin did not heal back to the acromion, so surgeons now will now access the rotator cuff tear by leaving the deltoid muscle attached and simply splitting it (like ‘peeking through closed curtains’) to gain access to the rotator cuff where it attaches to the humerus. This process is ideal for tears that have not pulled back, or retracted back away from the deltoid. However, in cases of larger retracted rotator cuff tears, working through a deltoid split can become a little like building a ship in a bottle—trying to work through the narrow mouth of a bottleneck to get to the retracted cuff tissue.
If you're going to use any injectable gear, then of course you're going to need some "darts." You can pick up syringes at your local pharmacy unless your state has certain restrictions. Also, you can purchase needles online. Just do a little searching around and you'll find several places that'll hook you up. Syringes will run you around 50 cents apiece. Note that it'll be more difficult to obtain needles (at least from the larger, more "legit" companies) if you live in California and Illinois. You'll usually need a doctor's prescription in those states. Still, if you look around enough, you can get what you need.