1. Bone Cell and Imaging Laboratory, Department of Orthopedics, Klinikum rechts der Isar; Ismaninger Straße 22, Technical University Munich; 81675 München Germany
2. Siegfried Weller Institute, BG Hospital; University of Tübingen, Schnarrenbergstraße 95; 72076 Tübingen Germany
3. Mineralized Tissue Laboratory; Research Division, Hospital for Special Surgery, 535 E 70th Street; New York NY 10021 U.S.A.