Generally, “tight” muscles are a result of an underlying disorder and not by themselves, the cause for symptoms.
There are no screws that protrude into the back of the neck. The anterior plate has screws that enter the vertebral bodies but nothing in the rear of the spine.
You might have facet generated pain if there is base of the skull symptoms.
A pseudoarthrosis can easily be determined by a set of X-rays including flexion/extension.