1. School of Engineering and Applied Sciences; Harvard University; Cambridge Massachusetts 02138
2. Wyss Institute for Biologically Inspired Engineering; Harvard University; Cambridge Massachusetts 02138
3. Julius Wolff Institute; Charité - Universitätsmedizin Berlin; Berlin 13353 Germany
4. Center for Musculoskeletal Surgery; Charité - Universitätsmedizin Berlin; Berlin 13353 Germany