作者单位:Harbor UCLA Med Ctr, Dept Orthopaed Surg, Los Angeles, CA USA[1]Univ Pittsburgh, Med Ctr, Dept Neurol Surg, Pittsburgh, PA USA[2]Mt Sinai Hosp, Dept Orthopaed Surg, New York, NY USA[3]Northwestern Univ, Feinberg Sch Med, Dept Orthopaed Surg, 676 N St Clair St,1350, Chicago, IL 60611[4]