Paediatric patients undergoing orthopaedic surgery can experience severe pain in the postoperative period. When pain interferes with mobilization and joint movement, the rehabilitation phase is prolonged and painful. Approximately 13% of the children undergoing orthopaedic surgery report symptoms of chronic pain. Therefore, optimal pain treatment should be provided during and after the surgical procedure.~Intravenous opioids or continuous epidural blocks are commonly used for postoperative pain treatment after open hip and femoral surgery. However, side effects like nausea and vomiting, urinary retention, or pruritus are often related to these treatments.~Lumbar plexus blocks (LPB) are a safe and effective alternative for postoperative treatment after hip and femoral surgery. Single injection LPB techniques have shown to provide good pain relief during the early postoperative period in children. Paediatric patients might also benefit from a catheter technique giving a prolonged postoperative analgesia. LPB provide simultaneous sensory blocks of the femoral nerve and the obturator nerve. Both nerves are primarily responsible for the innervation to the femoral shaft, hip joint and the pelvic bones. In contrast to epidural anesthesia techniques, LPB has only unilateral effect. Patients therefore achieve higher mobilization levels, resulting in early rehabilitation.~Several ultrasound-guided lumbar plexus block techniques have been described in the past. The Shamrock technique is a new LPB-technique that has shown to improve visualization of the lumbar plexus, surrounding anatomy, and injection needle. The improved visualization can facilitate block performance and improve safety. A catheter technique will be used for LPB to provide prolonged postoperative analgesia.~In a randomized controlled trial, the investigators will investigate under controlled circumstances the effect of a LPB-catheter placed with ultrasound guided Shamrock-technique to improve postoperative pain treatment after unilateral open hip and femoral surgery in paediatric patients. The investigators will investigate the effect on opioid consumption and the reduction of opioid related side effects during the first 24 postoperative hours.
Randomised controlled prospective trial with 2 groups (active group with Lumbar plexus block (LPB)-catheter vs control group). In a randomized controlled trial, the investigators will investigate under controlled circumstances the effect of a LPB-catheter placed with ultrasound guided Shamrock-technique to improve postoperative pain treatment after unilateral open hip and femoral surgery in paediatric patients. The investigators will investigate the effect on opioid consumption and the reduction of opioid related side effects during the first 24 postoperative hours