A herniated disk, sometimes (incorrectly) called a slipped disk, is a common cause of severe back pain and sciatica. A disk in the lumbar area becomes herniated when it ruptures or thins out, and degenerates to the point that the gel within the disk (the nucleus pulposus) pushes outward.
The ceiling fan's downrod must be long enough for the fan's blades to clear the ceiling. A fan with a 12-inch downrod works for a vaulted ceiling with a one-quarter-to one-third-inch pitch. An 18-inch downrod is sufficient for a pitch that is five-twelfths to one-half inch.
The table below is a general guideline for deciding what size fan you need, based on an 8' ceiling. Consider stepping up a size for higher ceilings for better efficiency and/or large pieces of furniture, like queen sized beds, for aesthetic appeal. The table below is a general guideline for choosing a downrod length.