1 Department of Orthopaedic Surgery, UC San Francisco, 500 Parnassus Avenue, MU320W, San Francisco, CA 94143, USA. Electronic address: Sigurd.Berven@ucsf.edu.
2 UCSF Department of Neurosurgery, 505 Parnassus Avenue, M780, San Francisco, CA 94143, USA. Electronic address: Praveen.mummaneni@ucsf.edu.