Dr. Nixon graduated fom the University of Sydney in 1978, practiced for a year and a half, and then completed a residency and research degree in large animal surgery at Colorado State University, leading to board certification in American College of Veterinary Surgeons in 1985. He worked at the University of Florida for 5 years before moving to Cornell University in New York in 1988, where he provided service in clinical orthopedics and neurosurgery, and served as chief of surgery from 2002-2006. He was also director of the Comparative Orthopedics Laboratory and JD Wheat Equine Sports Medicine Laboratory at Cornell University, and was the inaurgural Chief Medical Officer at Cornell Ruffian Equine Specialists, a Cornell owned equine private practice hospital alongside the Belmont racetrack in New York City. Besides his extensive experience in orthopedic surgery, Dr Nixon has a long career in musculoskeletal research, with grant support from numerous external agencies, including The Morris Animal Foundation., Grayson Jockey Club, Quarter Horse Association, The Arthritis Foundation, and the National Institutes of Health, for studies targeting cell and gene therapy for joint disease.  

He has over 200 published papers focusing on equine orthopedic disease and surgery, with a particular interest in minimally invasive surgery, cartilage injury and repair, and novel regenerative medicine approaches to joint disease in racing and sport horses. He is also editor and author of two books, Equine Fracture Repair (now in 2nd edition), and Diagnostic and Surgical Arthroscopy of the Horse (in 4th edition). Dr Nixon was inducted into the University of Kentucky Gluck Equine Research Hall of Fame in 2009, and awarded the American College of Veterinary Surgeons, Founders Award for Lifetime Achievement, in 2015.

Dr Nixon retired from Cornell University at the end of 2020, and continues his teaching, research, and clinical roles as an emeritus professor in equine surgery at Cornell, adjunct professor at the University of Florida, and as a consultant to several private practices in the US and abroad. He continues his teaching roles as a faculty member for the AO-Vet Fracture Repair Courses, and as faculty member in Equine Arthroscopy courses in the US and Europe.