[1] Univ Penn, Perelman Sch Med, Dept Surg, 3400 Spruce St, 4 Silverstein, Philadelphia, PA 19104 USA
[2] Univ Penn, Ctr Surg & Hlth Econ, Dept Surg, Philadelphia, PA USA
[3] Univ Penn, Perelman Sch Med, Philadelphia, PA USA
[4] Univ Penn, Leonard Davis Inst Hlth Econ, Philadelphia, PA USA
[5] Univ Penn, Perelman Sch Med, Dept Surg, Philadelphia, PA USA
[6] Univ Penn, Perelman Sch Med, Dept Family Med & Community Hlth, Philadelphia, PA USA
[7] Univ Penn, Perelman Sch Med, Dept Med, Philadelphia, PA USA
[8] Univ Penn, Perelman Sch Med, Dept Emergency Med, Philadelphia, PA USA