I as an orthopaedic surgeon
do not think that this is a primary case of back pain
Pain in the back could be referred from a primary site which in this case is most probably the kidney
Also I think that the underlying disease could be a kidney stone......since pain of such extreme nature occurs most commonly due to this disease.
Do consult a urologist
in addition to an orthopedician for expert opinion .
Start him on opiod analgesics for pain relief under strict specialist supervision .
I hope my advice has helped .
Goo luck .