Andrew J Engel1, Milan P Stojanovic2, Yakov Vorobeychik3, John MacVicar4. 1. Affordable Pain Management, 5600 N Sheridan Rd, #104, Chicago, IL 60660, USA. 2. Anesthesiology, Critical Care and Pain Medicine Service, VA Boston Healthcare System, 150 S. Huntington Avenue, Boston, MA 02130, USA. 3. Department of Anesthesiology, Pain Medicine Division, Penn State College of Medicine, 500 University Drive, PO Box 850, Hershey, PA 17033-0850, USA. 4. Southern Rehabilitation Institute, 29 Byron Street, PO Box 7549, Sydenham, Christchurch 8240, New Zealand.