[1] Univ Alberta, Sch Publ Hlth, Dept Publ Hlth Sci, Edmonton, AB T6G 2E1, Canada
[2] Univ Alberta, Sch Publ Hlth, Alberta Ctr Injury Control & Res, Edmonton, AB T6G 2E1, Canada
[3] Karolinska Inst, Inst Environm Med, S-10401 Stockholm, Sweden
[4] Inst Work & Hlth, Toronto, ON, Canada
[5] Univ Toronto, Dept Publ Hlth Sci, Toronto, ON, Canada
[6] Univ Toronto, Dept Hlth Policy Management & Evaluat, Toronto, ON, Canada
[7] Toronto Western Hosp, Univ Hlth Network Rehabil Solut, Ctr Res Expertise Improved Disabil Outcomes, Toronto, ON M5T 2S8, Canada
[8] Toronto Western Res Inst, Div Hlth Care & Outcomes Res, Toronto, ON, Canada
[9] Univ Calif Irvine, Dept Neurol, Irvine, CA 92717 USA
[10] Univ Calif Los Angeles, Sch Publ Hlth, Dept Epidemiol, Los Angeles, CA 90024 USA
[11] CUNY, Dept Orthopaed, New York, NY 10021 USA
[12] CUNY, Dept Environm Med, New York, NY 10021 USA
[13] CUNY, Sch Med, Program Ergon & Biomech, New York, NY 10031 USA
[14] CUNY, Grad Sch Arts & Sci, New York, NY 10031 USA
[15] CUNY, Occupat & Ind Orthopaed Ctr, New York, NY 10031 USA
[16] Univ Hawaii Manoa, John A Burns Sch Med, Dept Publ Hlth Sci, Honolulu, HI 96822 USA
[17] Stanford Univ, Sch Med, Dept Orthopaed Surg, Stanford, CA 94305 USA
[18] Stanford Univ Hosp & Clin, Orthopaed Spine Ctr, Stanford, CA USA
[19] Stanford Univ Hosp & Clin, Spinal Surg Serv, Stanford, CA USA
[20] Merck & Co Inc, Rahway, NJ 07065 USA
[21] Univ British Columbia, Dept Med, Vancouver, BC V5Z 1M9, Canada