I don't know if you're familiar with the father-daughter thru-hiking team of Balls and Sunshine from Salem, Oregon. While hiking the Appalachian Trail in Pennsylvania, Sunshine (age 12 at the time, I believe) fell and broke her arm. They took a few days off (relatives took them to the Hershey Medical Center, where they gave her a special weatherproof cast) and then continued, completing the trail (the next year, they completed the Triple Crown) Of course her dad did most of the heavy work for her.

If you use trekking poles, you probably want to use just one in your good hand. Mostly, you'll have the wonderful experience of trying to do everything one-handed. I hope you'll have someone with you to help out!

Does your physician know you're doing this? He might want to prescribe a different (i.e, more weatherproof) cast. If it's a plaster cast and gets wet, your arm will be toast.

Not quite the same thing, but two years ago my son participated as a re-enactor in the 150th anniversary of the Battle of Gettysburg, with a broken collarbone, 5 broken ribs and a few other lesser injuries, two weeks after a nasty fall from his horse and less than a week after collarbone surgery (which actually helped considerably). Of course he was subsisting on extensive pain medication. He took part in two battles (wearing a period-correct sling rigged up with the help of an orthopedic surgeon member of his cavalry troop) as "dismounted cavalry." (No way was he getting on a horse again until he healed up!) Joining the Federal infantry fending off Pickett's Charge on the third day involved several miles of hiking from the cavalry camp to the battle site and back again. If he made it through, you should be able to do your hike, as long as you can cope with being mostly one-handed. Let us know how it turns out!