When my husband had surgery and an extended recovery under FMLA, first we had to use sick leave time, then we could have used his vacation time, but after that it would have been unpaid. They would have had to hold his job for him...that's the provision. Also, where my husband works, oftentimes other employees donate hours to an employee who needs FMLA and hasn't built up enough time to cover their time off.
Luckily, he had enough sick time to cover his leave.
OT to the thread, but I do hope your husband has recovered.