[1] Emerson Hosp, Concord, MA 01742 USA
[2] Boston Univ, Sch Med, Boston, MA 02118 USA
[3] Univ N Carolina, Chapel Hill, NC USA
[4] Natl Ctr Catastroph Sports Injury Res, Chapel Hill, NC USA
[5] Brigham & Womens Hosp, Neurol Sports Injury Ctr, Boston, MA 02115 USA