The assault took place at the Yates bar on Silver Street, Halifax, in the early hours of Sunday, May 26.
Police were called to the bar at 12.30am.
A 41-year-old man was assaulted and his leg was broken.
A 28-year-old man was arrested.
He has been released while investigations continue.
Detectives are now appealing for witnesses or anyone with information to contact them on 101, quoting reference 13190266800.