1. Biomechanical Testing Facility, UCSF/SFGH Orthopaedic Trauma Institute, San Francisco, CA 94110
2. Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA 94110
3. Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA 94110 e-mail:
4. Department of Endocrinology, University of California San Francisco, San Francisco, CA 94110
5. Department of Neurological Surgery, University of California San Francisco, San Francisco, CA 94110