Have you tried taking magnesium citrate supplement? I suffered with fissures on and off for 10 years or more and had various creams from the GP. I was referred to a consultant 3 years ago, but in the meantime read on this forum that magnesium supplements could help relax the muscles and ease the spasms I was getting. As soon as I started taking the magnesium citrate the spasms eased and the healing process began. Fortunately it meant that I didn't have to go through with any surgery. I have continued to take these supplements ever since and if I run out and don't take them for a while, I start to get 'twinges' and take that as a warning sign and start taking them again. They may not work for everyone, but they are certainly worth a try if there's a chance they'll help. I swear by magnesium, it has totally changed my life and apart from the odd 'twinge' when I forget to take the magnesium, touch wood, I've been problem free since.
I think magnesium citrate is the better supplement of the magnesiums to be effective in this case. I take Solgate Magnesium Citrate tablets daily (200mg of magnesium each tablet, so 400mg a day) and easily available from Health Food Shops or via Amazon. Wishing you well!