1. Department of Neurological Surgery, University of Washington, Seattle, WA 98195, USA
2. Department of Bioengineering, University of California Los Angeles, Los Angeles, CA 90095, USA
3. Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA
4. Department of Orthopedics and Trauma Surgery, University of Cologne, 50931 Cologne, Germany