Agree with finding a studded/XC-type shoe, but the problem I had last winter was running every day, in the same shoe (~Kilkenny XC flats, only shoe I felt safe with), 100% on concrete/ice/snow. I strained my calf badly from slipping on ice, and I think it would have helped it heal faster if I'd be alternating different shoes to change the muscle usage/stress. That's what I'll try to do this winter, along with getting more on a treadmill when it's exceptionally slippy outside.