What are the best veggies that I can grow post my spine surgery?

You should be able to plant just about any herb in six inches of soil. Hubby could raise the depth by adding more wood to the sides fairly easily if he uses the little metal plates between them (I can't for the life of me come up with their name!). That will give you a good depth for veggies. The only problem with waist high is that anything that grows taller, like tomatoes will be hard to reach as they get taller. I would suggest for them, get a really big pot and sit on a stool to tend it that isn't too tall, it won't be long and it will be tall and much easier to care for that way, and also to get the tomatoes off the plant without using a ladder for the top of the plants. I planted a patio early girl last year in a huge pot and without the height of the pot the plant was five feet high, hubby had to harvest the uppermost tomatoes. My 5'3" just couldn't reach without getting out a ladder from the shed up the hill (I refused to lug the thing down the steep hill just for that). Good luck!

Anything that grows above ground. Beans, peppers, tomatoes

Have had a number of spine surgeries, make suture you get the best physical therapy post surgery that you can. It does make a difference in the long run. I am alone with a bunch of pets and it was a bit challenging the first few days home from the hospital. Feeding the pets, oh my, I made a mess. Anyway, grow things you like to eat, almost anything will grow in 6". Cucumbers, zucchini, peppers, beans, etc. Grow tomatoes in a jumbo pot with a trellis.

http://homeguides.sfgate.com/soil-depth-planting-vegetables-raised-bed-47491.html