The 24-year-old Welshman, who has been a vital part of a Cherries side unbeaten in their last 13 games, damaged ankle ligaments in Saturday's victory against Colchester and is ruled out until March.
And Howe, who recently described MacDonald as an unsung hero and a pivotal player who makes his side tick, is now weighing up how best to replace the former Yeovil man.
"I don't think we've got a Shaun MacDonald-type player like-for-like we can bring in," Howe told BBC Solent.
"It might mean we have to be a little bit more flexible in the way we set up. It may mean we have to be creative and although we do have players who can play a similar role, Shaun was unique in terms of his qualities.
"But whether we bring one in from within, or whether we tweak our system, or whether we look to bring a loan player in January, all options are available to us at this moment."
- Sports & Recreation