How Safe Is Taking Motrin For Floating Rib Syndrome?

My husband was diagnosed yesterday with a hands on exam by our primary dr, who tells him he has floating rib syndrome. The 12th rib. This is causing him great deal of pain. He had a spinal surgery ,11 hours long 7 months ago and wears plastic brace for support at all times except for bedtime. Percocet 7.5/325 is not releiving his discomfort. Any suggestions? I wondered if 800mg motrin would beneit him any.