1. Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA
2. Department of Orthopaedic Surgery, Tulane University, 1430 Tulane Avenue, New Orleans, LA 70112, USA
3. Department of Biostatistics, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205, USA