I hate to be the bigmouth here.
A pain clinic is fine. But a pain clinic treats symptoms (pain), not a disease. You might give your mother cough syrup if she had lung cancer. It may even stop the coughing. But there is a bigger picture. Often times, much, much bigger.
You mentioned DDD. I'd be looking for a good Neurologist. The pain can mean any number of things. But until a qualified specialist clinically evaluates your mother, views her films, etc., nobody is going to know exactly what needs or doesn't need to be treated.
Maybe it's just some inflammation. Maybe nerves are being compressed, which can lead to long term damage. Maybe even the spinal cord is involved.
A good Dr., along with the appropriate tests and exams, should give you some answers.
I hope your mom finds some relief soon!