What Causes Bald Patches On Head On Healed Scars?

My husband had hair line fractures to the skull when a child he had three small scars on the back of his head. He has recently knocked out by someone hitting him and he hit the back of his head since then the small scars have become big bald patches on the back of his head. would this be due to the him hitting the back of his head when he fall back?