Hance Clarke, University Health Network (IMAGE) University Health Network Caption A team led by Dr. Hance Clarke, Medical Director of the Pain Research Unit at Toronto General Hospital (TGH), University Health Network (UHN), pictured here, estimated that about 15 per cent of complex postoperative pain patients develop moderate to severe chronic, post-surgical pain, have significant disability, and continue to use opioids for pain relief long-term. Credit UHN Usage Restrictions Please credit UHN. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.