Could ankylosing spondylitis cause ligamentus flavum hypertrophy s1 through entire lumbar region and significant spur formation entire cervical spine?

Yes: The more likely finding is ossification of ligamentum flavum the rest sounds like its a possibility check with a pmr doctor or rheumatologist the x-rays usually give a pretty good idea.

Probably not: This sounds more likely to be osteoarthritic changes. While ank spongy causes calcification of the spinal ligaments, true spur formation is an osteoarthritic characteristic.