Nat,
I've been thinking about you and hope you are doing better. I hope you are easy on yourself and your expectations for ROM and healing at this point. There's no way to know how the SC and your previous surgeries will impact the healing process now. SC is so rare and people with SC who have had joint replacement are even more rare. Your healing experience may follow its own unique path. Martha's post-TKR posts on the SC forum may be closer to what you may experience, although I can't remember how long she had SC and how many previous surgeries she had. I only had one arthroscopic surgery (and no open procedures) before my hip replacement, so scar tissue wasn't an issue.
I hope the new meds are giving you better pain control and helping with the twitching. I had a lot of twitching earlier, but it has stopped now. If you are not comfortable, ask for something different.