We came across this article from BBC Nature that documents research on hibernating black bears, proving that their recuperative powers are truly amazing.
Injured bears that enter dens in the winter to hibernate, some for as many as 7 months, emerge the following spring showing little or no trace of their injury.
We have actually witnessed this, during several years when we volunteered at a wildlife/bear sanctuary in northern Minnesota. We saw several bears that left the area in the fall headed to their home ranges to hibernate with injuries that appeared to be life-threatening. But when these same bears returned to the area the next spring or summer they were healthy and the injuries had disappeared as if by magic.