if you had a fusion at C4-5 above a prior C5-7 fusion that did not go on to fuse (pseudoarthrosis), this is not uncommon depending upon the graft used for fusion.
If this level did not fuse but the hardware is not loose or broken, you have a stable pseudoarthrosis. About 50% of pseudoarthroses do not cause pain and can be left alone. There is a higher chance of pain activation with injury due to the “less stable” nature of this pseudoarthrosis but still can be left alone if your symptoms are tolerable (“some neck pain/stiffness that is constant but not bad and doesn’t require any painkillers”).
Your current imbalance symptoms (“Leftover is some intermittent numbness in my hands/feet, some weakness, some balance/clumsiness issues (I would fail a field sobriety test”) are probably residual symptoms from the previous cord compression as long as you don’t have ongoing canal stenosis (narrowing).
Dr. Corenman
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.