You do not mention if the approach was posterior or anterior (through the belly) or both. After any big surgery, you can develop an ileus, a temporary paralysis of the intestines. This condition typically disappears within a week.
Pain and pressure around the ribs can originate from intestinal disorders but don’t forget that nerve irritation can also cause this. If you had a thoracic surgery with correction of deformity, nerve stretch or even instrumentation stenosis (a screw irritating a nerve root) can also cause this.
Check the sensation around your chest and abdomen. If there is a numb patch or a very irritable and sensitive band of skin in or around the area of your abdominal pain, this could be nerve irritation.