Final answer:
The best candidate for a lumbar steroid injection is a 72-year-old woman with severe central spinal stenosis, multilevel degenerative disk disease, ligamentum flavum hypertrophy, and facet arthropathy.
Step-by-step explanation:
The best candidate for a lumbar steroid injection would be Option A: A 72-year-old woman with severe central spinal stenosis at L4-5, multilevel degenerative disk disease, ligamentum flavum hypertrophy, and facet arthropathy. The patient's symptoms of new onset right lower-extremity pain and the MRI findings are indicative of nerve compression and inflammation in the lumbar spine, which can be relieved by a steroid injection. This option also rules out the other patients who either have refractory low back pain, post-surgical complications, or a mild disc bulge without significant stenosis or radiculopathy.