1Department of Orthopaedics and Rehabilitation, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, Iowa 52242. E-mail address: john-flint@uiowa.edu2Department of Orthopaedic Surgery, University of Tennessee-Campbell Clinic, 1211 Union Avenue, Suite 510, Memphis, TN 381043Department of Orthopaedic Surgery, Medical Arts and Research Building, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06034-40374Department of Orthopaedic Surgery, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104