1. Emory Spine and Orthopaedic Center; Atlanta Georgia 30329
2. Department of Biomedical Engineering; Georgia Institute of Technology and Emory University; Atlanta Georgia 30030
3. Schulich School of Engineering, Department of Mechanical and Manufacturing Engineering; University of Calgary; Calgary AB T2N 1N4 Canada
4. Swanson School of Engineering, Department of Bioengineering; University of Pittsburgh; Pittsburgh Pennsylvania 15213