He had been due to join up with Middlesex in April for a spell of eight County Championship fixtures and the Vitality Blast.
Middlesex’s director of cricket, Alan Coleman, said: “We are naturally extremely disappointed that Keshav will not be joining Middlesex this year after sustaining this freak injury and we are saddened to hear that he will face a significant absence from playing. It goes without saying that everyone at the club wishes him a speedy recovery.
“For us to lose Kesh so close to the start of the new season is a blow, however he wasn’t scheduled to begin playing for us until late April, which buys us a little time to put Plan B into action. We will of course keep everyone updated on the situation regarding a replacement overseas player for the coming season.”