Do I have a case against my Township?

Possibly: you may have a claim or case if--
1) The township was negligent or unreasonably careless in not treating (e.g. one or more of plowing, sanding, or salting) the road. The key word is "unreasonably": the law accepts that someone (including a town) only has to take reasonable steps and is not held to a standard or preventing all risk. If the town did treat the road the way towns typically do, even that if that treatment did not eliminate all ice, they did what they are supposed to and are not liable. Or if the ice had formed (or was still forming) recently enough (compared to when you fell) that it was not  reasonable to expect they would have gotten to it yet (the law accepts that they can't act instantly; it takes time to get to/treat all the roads in town), they again did nothing wrong and are not liable. You'd have to show that they failed to treat the road in a reasonable way within a reasonable time frame after knowing, or when the logically must have known, there would be ice, and in making the determination of what is "reasonable," you would compare to the anti-ice measures generally taken by towns for their roads.
(Obviously, they are only potentially liabe for a town-controlled road: the county or state could be liable for county- or state-controlled roads, and a private property owner for a private road.)
2) You'd also have to show that you did not contribute to your accident and injury through your own unreasonable carelessness. For example, if you were running or jogging when it was reasonable to think it was icy out, that would be careless and would reduce or possibly eliminate the compensation you might otherwise get.