The Coflex implant is not designed for the treatment of lower back pain. It is a device that sits between the spinous processes and induces flexion of the vertebra. Flexion of the spine will load the discs. If the back pain is generated from the discs (as it typically is), then this device will increase the load on the discs and increase lower back pain.
You have concerning weakness of both the L5 and the S1 motor groups (see section under “nerve injuries and recovery” on the website for further explanation. What you need is a back pain workup from a thorough spine surgeon who can also explain why you have weakness.