West Midlands Police said a man in his 40s was forced to undergo surgery on his arm after being attacked on Waterloo Road in Smethwick at around 9pm on June 23.
It is understood that a group of men were involved an officers have been carrying out CCTV enquiries in the area.
A spokesperson for West Midlands Police said: “We’re keen to hear from anyone who can help our investigation, particularly anybody who was passing through the area at the time and has dashcam footage.
“You can contact us via 101 and quote 20/290765/25.
“Alternatively, you can call Crimestoppers anonymously on 0800 555 111.”