This clinical trial is focused on improving pain relief after a surgery called total hip replacement, which is performed under spinal anesthesia. The study is investigating the effectiveness of using intrathecal morphine, a type of pain medication injected into the spinal area, with or without another medication called ropivacaine, which is used in a specific type of nerve block known as the suprainguinal fascia iliaca block. The goal is to see if these treatments can help reduce pain and improve comfort when moving around after the surgery.

Participants in the study will receive either the pain medication or a placebo. The study will monitor pain levels using a simple scale from 0 to 10, where 0 means no pain and 10 means the worst pain imaginable. This will be checked 8 hours after the surgery and at various times over the next two days. The study will also look at how much additional pain medication is needed during the first 48 hours after surgery and will track any side effects or complications that might occur, such as nausea or dizziness.

The study aims to provide valuable information on how to manage pain effectively after hip replacement surgery, potentially leading to better recovery experiences for patients. Participants will be asked about their pain experiences and overall recovery at different points in time, including the first and second days after surgery, as well as one week and one month later. This information will help assess the overall quality of recovery and the effectiveness of the pain management strategies being tested.