Can relate some experiences about turbo-ing with fractured limbs - in my case, a duathlon crash (don't use time trial slicks on country lanes...) left me with 1 broken toe, 1 fractured wrist and 1 snapped humerous - not funny at the time.
Wrist and funny bone were same arm. Was in plaster from elbow to fingers.
With doctor's kind-of permission, I worked out that I could change the pedals on the turbo bike to rat-traps and ride with a flip-flop on my plastered right leg (below knee to toes) and spin the cranks without flexing the ankle too much. I needed to do this because I was preparing to ride the Marmotte. (Crashed on May Day appropiately enough - Marmotte in early July = 12 weeks recovery).
So, broken toe not a problem. The Doctors knew of this plan and didn't say I couldn't (or shouldn't).
Problem was my arms - my good left arm just wasn't up for to the task of hour long turbo sessions. It wasn't until the pain and swelling in my arm (post-pinning operation) had gone down that I could prop my mid forearms on a tri-bar, so spread a bit of weight onto both shoulders / upper arms. At least the Doc signed me off work and I wasn't allowed to drive, so I had nothing better to do than sit on the turbo and keep my thighs in trim... Beats daytime TV.
With your shoulder snag - then one shouldered weight bearing will probably be your limiting factor.
Perhaps you could rig up a chest-cushion arrangement? You need to get into your "normal" back position otherwise you'll get different saddle pressures from sitting too upright, or lose any lower back strength.
Still, I succeeded.
Rode from Geneva to Bourg D'Oisons, one armed mostly, rode the Marmotte just missing gold for my age group, then got on the cover of Audax Calendar 2006 climbing Alpe D'Huez, so things can be done.
Best of luck...
