There are many reasons as to why the skin becomes crepey on an individual. Aging, smoking, excessive sun exposure and most importantly, weight loss. Most individuals lose fat and muscle mass everywhere from head to toe as they age. That results in a deflated balloon like appearance making the skin which is now in excess look creepy. In order to restore the volume in your arms you would probably need quite a bit of Sculptra, but it can be done effectively. The Creepyness will go away once the arms have restored the volume for before the crepeyness appeared. No one knows exactly how many vials of the product it will take. You can also start using a derma roller on regular basis which will stimulate collagen production in the skin itself. I hope this helps and good luck from New York City plastic surgery