Can having metal rods screwed to your lower back reduce sensation in your vaginal area?

Possibly: Any disruption of the nerves can cause changed sensation. The sensory nerves of the genitals pass through the lower back (lumbar and sacral) and may be affected. It may be the the back damage that lead to your back surgery is the cause of your problem. If the surgery is recent, you may have some improvement in time . Nerves heal very slowly, so patience is important.

Vaginal area?: You indicate that you are a 47 year old male. Harrington rod placement should not have any impact on your gender. At least not the standard size rods.

Not unless: The nerves to that area were somehow disturbed during the surgery. Talk to your spinal surgeon