A thought on your shoulder... I too have an permanently injured should and now have to use my non-dominant arm for pretty much everything. The type of leashes I use have a swivel snap hook and the lead itself has grommets pretty much it's entire length. This means I can snap the leash around my waist or loop and snap across my body and over a shoulder. Being able to do this leaves me hands-free more or less should I choose but, moreover what it does is give me two hands and the weight of my entire body to work with as a means of steadying and counter-balancing the weight of big dogs doing what big dogs do.
I bought mine but you could easily make one. I posted a thread about it here. http://www.pets.ca/forum/showthread....y+poochy+leash