Sole caretaker needing surgery and feeling guilty. Any advice?

Sooner, I'm reading your past posts and your mother sounds like she has been selfish and hurtful toward you and your wife. What kind of mother complains about "feeling neglected" because her son's wife had cancer?

If your mother is 97, you're probably in your 70s? Your mother's needs are only going to increase. You need a long-term plan that does not include being the sole caregiver to your mother.

Schedule the knee surgery. Schedule your mother for a respite stay. Why won't they accept her full-time when they have a spot for her for respite?

You have given up your life the past 15 years since you took your parents in! And the stress affected your wife. I am so sorry that the past 15 years weren't different for you (and for her).

What do you think will happen if you don't get the surgery? What happens when you can no longer physically be your mother's 24/7/365 caregiving slave?

You do not indicate what caregiving you do for mom.
Your mom can pay for caregivers to come in while you recover from surgery AND while you rehab.
You can place mom in a facility that will be appropriate for the level of care that she needs. (MC if she has dementia or AL if she can manage some things on her own) Mom pays for the time that she is in respite stay. AND she should be there for a while not just your day of surgery, allow yourself rehab time. (If you do rehab in a facility for more intense rehab it is possible that you might be in the same building)
If mom is on Hospice Hospice will cover almost 1 week of respite so you can have surgery and a few days to recover once she is home caregivers should come in to help you out with her.

Isnt this the same mother who complained that you neglected her while you took care of your wife while she was dying from cancer?

Your mom is a selfish you know what. Put her in respite. Get your knee surgery and take care of you.

Personally I would leave her in a nursing home permanately.

Please take care of yourself and schedule the surgery. Arrange care for your mother, either in assisted living or having caregivers come in. And don’t go into having others providing the care assuming it won’t be good or go well, you and mom both may just find it a good experience. My dad had much needed knee replacement and did very well afterwards, went through physical therapy, and was pain free and recovered. My FIL has stubbornly refused to do it, though he’s been told many times it was needed. He now walks slowly and is slumped over in discomfort. This won’t improve. A healthy mother would want you to do what’s best for you, after all you’re no good to her if you’re not healthy yourself. I’m sorry for the loss of your wife, what a huge life change. I wish you healing and peace