Koop, Winter, and Lonstein method of occipitocervical fusion used when posterior arch of C1 is absent. A, Exposure of occiput, atlas, and axis. B, Reflection of periosteal flap to cover defect in atlas. C, Decortication of exposed vertebral elements. D, Placement of autogenous cancellous iliac bone grafts. SEETECHNIQUE 43.6.