1 Department of Epidemiology and Biostatistics, Joe C. Wen School of Population & Public Health, University of California, Irvine, CA, 92697-7550, USA.
2 Department of Biomedical Engineering, University of California, Irvine, CA, USA.
3 Department of Orthopedic Surgery, University of California, Irvine, CA, USA.
4 Department of Epidemiology and Biostatistics, Joe C. Wen School of Population & Public Health, University of California, Irvine, CA, 92697-7550, USA. lhjiang@hs.uci.edu.