1. Kaiser Permanente Northern California Spine Care Program, San Jose2Division of Research, Kaiser Permanente Northern California, Oakland
2. Kaiser Permanente Northern California Spine Care Program, Redwood City
3. Kaiser Permanente Northern California Spine Care Program, Roseville
4. Division of Research, Kaiser Permanente Northern California, Oakland5Sutter Health Research, Development, and Dissemination, Walnut Creek, California
5. Division of Research, Kaiser Permanente Northern California, Oakland
6. Kaiser Permanente Northern California Spine Care Program, San Jose
7. Orthopedic Spine Surgery Division, Department of Orthopedics, Stanford University, Palo Alto, California
8. Division of Research, Kaiser Permanente Northern California, Oakland7Department of Medicine, University of California, San Francisco8Department of Epidemiology and Biostatistics, University of California, San Francisco