Singh K, An HS, Samartzis D, Nassr A, Provus J, Hickey M, Andersson GB. A prospective cohort analysis of adjacent vertebral body bone mineral density in lumbar surgery patients with or without instrumented posterolateral fusion: a 9- to 12-year follow-up. Spine (Phila Pa 1976). 2005 Aug 01; 30(15):1750-5.