The only thing I know about surgery is that it's not always an option. It depends on the hen's anatomy and that can only be determined on the table.
If you have a vet willing to give ot a go, do it.
@ManueB has more experience than I do. The cost was rather prohibitive where I live, so there I've only tried it once. It worked as expected, that is, the effect lasted for a few months.
She jogged a couple of weeks ago (after her first round of antibiotics) which gave me great hope, but she slipped back into her decline.
The second round of antibiotics gave her a couple of good days. But she was suffering since Wednesday and it was only right that we helped her along at her...
In Australian terms that's $38 for 3.5kg.
Prices here are in the same ballpark. I found a 3kg bag for $35. They also offer 14kg for $76, which is good value.
I'll keep it on the list, but I think I may try woodshavings first, which are more readily available.
I ran the suggestion of changing the nest box bedding past the vet who said, "It's her genetics - her ancestors were selectively bred for egg production and slaughter; not for reproductive health and longevity. Really, it's not your husbandry; don't you have that other old hen who's doing ok?"...
Thinking about it, there would be all sorts of nasties on straw. Mouse pee, fox poop, who knows what from out in the fields.
No doubt wood shavings are cleaner. After all, timber has to be clean enough for people to handle.
I've always used straw but Mary's lesion is a symptom of uterine infection. Nest box hygiene is a casual factor in uterine infections so of course I'm looking into alternatives to straw.
According to an AI, hemp is cleanest as it has some inherent anti microbial properties. I haven't looked into it any further yet, I'm too busy at work, but I will.