Clearly, high heels place more strain on the feet, ankles, knees, and low back than do flat shoes. But the body, when it works well, can tolerate a great deal of 'imbalance'.
But there are some particular issues worth bearing in mind for those of you with a spinal problem who want to wear heels.
The easiest way to explain it is to say that heels cause a tilting back of the lumbar spine (low back) and the neck. It therefore stands to reason that if your problem - even when wearing no shoes - is that you find bending backwards in the low back or neck causes pain or stiffness, then high heels are likely to aggravate this problem.
But if you find that you are quite ok bending backwards, but it's other movements that cause you problems, then you may well get away with heels.