They straightened the spine but didn’t have the ability to correct the rotation, so a telltale rib hump still protruded after surgery. Audrey wanted a straight spine, but not the rib hump, the bulge that often remains after surgery. Scoliosis surgery becomes the only option when the spine curve is greater than 40 degrees. Scoliosis causes the chest to twist, which creates a hump on the back as the ribs on one side stick out further when bending. This abnormality can be difficult to correct with surgery.