Over the last decade, a small group of prominent surgeons from around the country has been enlisted by medical device-maker Medtronic to do clinical research or write articles about the company's new spine surgery product. This year alone, many of those doctors received payments of hundreds of thousands to millions of dollars each in royalties for a variety of other Medtronic spinal devices, according to a Journal Sentinel analysis of newly released company payments. Medtronic began disclosing the payments this year, in advance of a federal requirement set to take effect in 2013. Since it won approval for narrow uses in 2002, the product - bone morphogenetic protein-2, known as BMP-2 - has been an increasingly dominant force in spinal fusion surgery, with sales of about $800 million a year, often for use in other procedures. Independent doctors say the product's success is due largely to positive findings made by the surgeons affiliated with the company.