Post-Operative Urinary Retention on Revision Knee Arthroplasty: the Role of Intrathecal Morphine

Revision total knee arthroplasty (rTKA) is a frequently performed procedure. Adequate pain management is an important feature, especially for fast-track and Enhanced Recovery After Surgery (ERAS) programs. The multimodal approach, including single shot or continuous nerve blocks with catheters and spinal or epidural morphine, is a stablished strategy. Although the administration of intrathecal morphine (IM) has been shown to significantly reduce pain scores, it is not free of adverse effects. Postoperative urinary retention (POUR) is possible and might increase the risk of periprosthetic infection. The purpose of this study is to compare patients undergoing rTKAS under spinal anesthesia with IM to patients undergoing the same procedure, under the same anesthetic technique, but with no IM, for POUR and postoperative pain related outcomes. All patients will have single shot and continuous adductor canal block (CACB) and single shot IPACK (interspace between the popliteal artery and the posterior knee capsule) block. The hypothesis is that postoperative pain control is comparable between the groups, with lower incidence of POUR in patients with no IM given.