About two weeks ago, Artturi Lehkonen went headfirst into the boards, and it was his neck and spine that absorbed the impact.
According to information from insider Elliotte Friedman, his injury is very serious, and he will be out for a significant amount of time, so much so that the Avalanche is looking to acquire another forward to compensate for his loss.
It's really unfortunate because if it's an injury related to the vertebrae, it could potentially end his career. There are players like Max Pacioretty (the infamous hit by Zdeno Chara) who recover, but it depends on the location of the impact for recurring pains to occur.