By Monica E. Oss Looking back at 2018, one of the developments that most caught my attention was the number of “mega-collaborations” between health systems and health plans. These collaborations are changing how care is delivered, and coupled with the just released Medicare ACO risk rules, will have more importance in the year ahead (see CMS Finalizes “Pathways to Success,” an Overhaul of Medicare’s National ACO Program). And, this shift brings great opportunity and great peril for specialty provider organizations serving consumers with complex needs. These collaborations have taken many forms. There is the merger and acquisition model of provider organizations: This past year, Humana acquired Kindred…