Thanks very much for the update, that’s fantastic that you’re able to cycle!! That is really good news! The fact that this exercise doesn’t increase pain etc suggests that you don’t have active arthrofibrosis (which involves inflammation). It’s good that you’re taking the exercise carefully though.
That’s really interesting about the Pendulum Pedal, I didn’t know that. Maybe I need to add a new web page for things that people have found to be helpful. What do you think?
Regarding your bad back, myself and many people I know have back trouble, and have found the a stretch in the McKenzie method transforms a really bad back into a normal one – so long as the stretches are done every day. I make them part of my normal daily routine, like brushing my teeth, and it only takes a minute or two. A friend recommended the book to me years ago, see https://www.mckenziemethod.com/products/pain-relief-self-treatment-books/mckenzie-method-treat-your-own-back-book/ If you go to this link you can see the book is open to a page of showing the stretch that I do, I don’t worry about the other stretches.
Regarding more surgery, I do have a cautionary approach. Surgery does help some people, but since you have Dupuytrens the scar tissue is likely to return. In addition, there is an increased risk of infection because you have a prosthesis, and of course there is always the risk that your arthrofibrosis will become active due to another injury (surgery), and you could end up much worse off. If I were in your position I would keep riding your bike carefully and within your limits, and yes, I do think that over time you will slowly increase your ROM. Because your inflammation appears to be under control, your body should be able to slowly break down the scar tissue. However, there is always the question of how your Dupuytrens will influence this process – that is an unknown, at least to me. A rheumatologist my know more about your response.
Also, to be frank, I’m not aware of a rehab centre anywhere in Australia that is knowledgeable and experience in treating arthrofibrosis. This is a very rare thing anywhere in the world.
I look forward to hearing how you go.