I suffer from some pretty severe soft tissue problems including burning/pain from traditional HID use (Human Interface Device such as mice). Mice are extremely problematic and turn my hand into a clam after long periods of use as well as severe burning in my forearms and even up to my shoulders.
This is why I do not use mice if at all possible. On my DAW I use a Kensington Expert Mouse (the name is misleading... it is a large trackball)...
http://www.amazon.ca/Kens...rt-Mouse/dp/B00009KH63 It is a much more natural and physically ergonomic interaction with the computer. You are just moving your index and and middle fingers to move the cursor and it is ultra precise (great for editing and fine parameter adjustment). This is much better than using your whole arm to move a mouse around on your desk while gripping the device (which also saves on deskpace because the trackball stay in one spot... no mouse pad needed). The other benefit is you use the edge of your thumb for left clicking (which is the most repeated click action obviously) on the HUGE button which is where it lays naturally when you have your hand on the device and your pinkie engages the right click. Then you have two compltely separate buttons at the top for other stuff where you just reach out with your index and ring fingers to engage. There is a scroll "ring" that surrounds the trackball that is really pleasurable and natural to use (unfortunately mine is corroded after years of abuse and I got mine used but I used to use my ring finger to scroll).
Essentially it is like just resting your hand on your desk and fiddling around with your fingers a little to execute elaborate actions that are a total PITA with a mouse. It still causes some pain after a while but no where near as much as mouse. The are unfortunately rather expensive but definitely worth it for many reasons. I really want to get a new one so I have a proper scrollwheel again.
The other device that causes less pain for me but is far less convenient or accurate are simple trackpads on laptops. Just dragging my finger around the pad seems to be better for my arms BUT the buttons are generally inconveniently located and awkward.
However I'd imagine there are much more ergonomic external trackpads one could use with better button positioning and more features. There are things like Wacom tablets that might work as hyper advanced trackpads but I've never used one so I don't know.
To me touchscreen would cause MORE pain and it would be far less localized than just in my arms. Having to reach out all the time to do stuff would wreck my shoulders and due to the full body adjustments to do so would likely bork out my back.
There are tablet apps that can be used to provide more control that regular Sonar touch stuff can offer (and have been around before Sonar even introduced touch capabilities) but from what I've read many of that stuff is kind of hit or miss.
Now if you want a TRUE touch solution, and I think it might be something I could use, you could drop tens of thousands of dolloars on one of those fance Slate units (Viper?) that are essentially an integrated console/control surface. They are almost like a table top arcade game unit that maps to EVERYTHING and provides quick mapping to pretty much anything you want/need. Not sure if they have programmed in a Sonar preset and really they are for pro studios but they sure are purty and fun to drool over.
Anyhoo... good luck with the pain. It sucks. The trackball/trackpad solutions may be your best/affordable options. Also try to ice and heat your tender bits after long sessions (ice for 10 minutes, heat for 10 minutes, repeat once) and see if you can get in to a sports injury clinic/physiotherapist to learn some stretching techniques to minimize the tension. I have a series of exercises I do to avoid/deal with flare ups in my arms. They are unfortunately difficult to put into text.
Cheers.