1. Center of Experimental Orthopaedics Saarland University Medical Center and Saarland University D‐66421 Homburg Saarland Germany
2. Department of Orthopaedic Surgery Saarland University Medical Center and Saarland University D‐66421 Homburg Saarland Germany
3. Department of Anaesthesia Boston Children's Hospital and Harvard Medical School Boston MA 02115 USA
4. Institute for Clinical and Experimental Surgery Saarland University Medical Center and Saarland University D‐66421 Homburg Saarland Germany