1. Department of Orthopaedic Surgery, Eberhard Karls University Tuebingen, D‑72076 Tuebingen, Germany
2. Department of Orthopaedic Surgery, Laboratory of Cell Biology, Eberhard Karls University Tuebingen, D‑72072 Tuebingen, Germany
3. Department of Hematology and Oncology, Children's Hospital, Eberhard Karls University Tuebingen, D‑72076 Tuebingen, Germany