Is it common for the septum to be removed from it's bony attachments?

Removing the septum from its bony attachments are only used if it is necessary to do so.  If a septum is so severely deviated, some rhinoplasty surgeons will perform an extracorporeal septoplasty, where the septum is completely removed, straightened on the back table, and then replaced into its anatomic position.  Quick summary: it's only performed when it is truly necessary.  

 A septoplasty is performed for medical necessity to improve air flow through the nose, and has no bearing on the shape of the nose when performed.The nasal septum is composed of several components which include the quadrangular cartilage, the bony vomer, the bony  perpendicular plate of the ethmoid and the bony nasal spine. Any one, or all these can be a component of creating a breathing issue out of the nose, for which a septoplasty can improve the airflow. It is common to remove, replaced or straighten the components of the septum to improve breathing. A rhinoplasty is performed for purely cosmetic purposes to improve the appearance of the nose and has nothing to do  breathing. Both a septoplasty and a rhinoplasty can be performed at the same time under one anesthetic with one recovery period.

Removal of the posterior septum from the bony septum (ethmoid, vomer) is actually quite common during septoplasty if that portion of the septal bone and cartilage is deviated. If performed properly this is safe. Removal of the septum from the nasal spine is typically only performed if the caudal septum (between the nostril openings) is severely deviated. This can create additional issues therefore the septum isn't routinely separated from the nasal spine unless there is a strong reason to do so. I hope this information is helpful for you.Stephen Weber MD, FACSDenver Facial Plastic Surgeon