Sorry to hear about your injuries. Best wishes for a good recovery.

***
I was wondering if you are significantly above average in weight or strength, or if you were accelerating particularly forcefully?

If you still have that chain, and there is some kind of manufacturing defect, there may be a possibility that you're due some kind of compensation.

***
I could be wrong, but I think that sometimes manufacturers in the bike industry cut it a little too close, in the interests of lighter weight.

In recognition of this, and to correct it, Bruce Gordon has said that he learned to include some extra weight and beef in his bikes and gear, to provide more of a buffer zone against failure.