The spine is not actually fused at the time of the surgery. The surgery actually creates the conditions for the spine to be able to fuse. Fusion is a process that can take anywhere between 6 and 18 months.
The first few months following surgery will likely be very limiting for the patient. Patients may also require prescription painkillers, muscle relaxants, or anti-inflammatory drugs after fusion surgery. Medications may have serious side effects, so always consult with your doctor.