A policeman has been bitten and received two fractures to his hand while making an arrest in Sydney's west.

Police were conducting a routine vehicle stop in Fairfield at 9.45pm (AEDT) on Friday when a 46-year-old man became aggressive and allegedly bit the policeman on the forearm.

The policeman and the man were involved in a violent struggle, which left the officer with two fractures to his hand, police said.

The man was charged with assaulting police, hindering police and not complying with police direction.

He has been granted bail and will face Fairfield Local Court on March, 11.