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.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.