I received this comment from the blog about the woman 29 years after Harrington rod fusion by Dr. Ralph Coonrad:

“I am 58 years old and I had my Harrington rod put in when I was 15 which was 43 years ago (where has the time gone) at the Royal Southern Hospital in Liverpool.  I am now developing other medical complaints which could require an MRI scan, Is this possible.  Has anyone experienced this at all PLEASE HELP”

My response to this is that most patients can have MRI’s done after spinal instrumentation.
The only issue is that the images will be a little blurry directly around the hardware, especially if it is stainless steel, which the original Harrington rods and many of the older systems used.
Pacemakers and spinal cord stimulator and intrathecal pumps can’t be used with MRI.
Certain metal clips in brain, etc may also be contraindication, or if you may have any metal fragments in your eye.

CT scan is an alternative way to look for spinal issues in patients with spinal hardware, which still has some artifact, but not as much as MRI.

For this particular person, she/he should discuss these questions with her doctor in context of her medical history and complaints.
I hope you get some answers and relief!

Dr. Lloyd Hey
Hey Clinic for Scoliosis and Spine Surgery
https://www.heyclinic.com