I have had pretty severe 'shin bang' for the last year and a half. It is certainly caused by backseat landing. Not landing in the backseat is a good first step, but this can't always be helped. The true cause however is a poor fit in the ankle area of your boot. 95% of boots can't get tight enough around the ankle and even with them clamped as hard as they can be, you probably can still lift your heel a little if you really try. That is the problem. The only way to really fix the situation is to get boots that fit perfectly and don't permit ANY heel liftage no matter how hard you try. Unfortunately, the solution for me was to get very VERY expensive custom fit boots. Nothing else helped over the last year or so. Possibly one of the most frustrating things ever. Hope this helps, good luck.
