For a second I thought you were going to say...."Most GPs can't, same goes for many physios, osteos.....but Chiros can! Phone 071 234..."
I see what you are saying about accurate diagnosis and practitioner selection. However in this case the steroid injection brought symptomatic relief suggesting it was accurately placed.
I think he should stay with his current practitioner for the moment. Again, it's tricky over the net to work out what's going on. I'd like to know how long the numbness lasts for example...