Physio Jon Fearn told readingfc.co.uk, "Marcus had an operation on Wednesday, with two plates and16 screws inserted into his hand.
"It's quite a nasty fracture. One of the bones is in five pieces but we're still aiming for a return in pre-season."
The clash in the 23rd minute ended Hahnemann's season 67 minutes early. Adam Federici completed the match in goal.