1. Department of Osteology and Biomechanics; University Medical Center Hamburg-Eppendorf; Lottestrasse 55A Hamburg 22529 Germany
2. Department of Pathology; University Medical Center Hamburg-Eppendorf; Martinistrasse 52 Hamburg 20246 Germany
3. Institute of Experimental Physics, University of Hamburg; Luruper Chaussee 149 Hamburg 22761 Germany
4. Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital; 25 Orde Street Toronto Ontario M5T 3H7 Canada