The anesthesiologist may have difficulty in passing a breathing tube down the trachea (windpipe) so that the airway can be maintained during general anesthesia for surgery. This is a potential problem in anyone with a rigid spine, especially if you also have forward stooping of the neck and a reduced jaw-opening capacity. An instrument called a fiber optic laryngoscope helps in putting the breathing tube down the trachea. However, someone with extreme neck deformity may require a tracheotomy. Post-surgical lung complications are also more likely, owing to severely restricted chest wall movement.

Lumbar spinal anesthesia or other alternatives to general anesthesia, such as epidural anesthesia, may be possible for some surgical procedures (e.g. total hip joint replacement surgery). However, lumbar puncture for spinal anesthesia is often not possible in AS patients with a fused lumbar spine.

Do not assume that healthcare providers are fully aware of all the limitations due to [spondylitis]. You should discuss any concerns or apprehensions with the surgeon, and arrange a preoperative consultation with the anesthesiologist. The anesthesiologist should examine you beforehand to find out your limitations, and also allay any concerns you may have. This should preferably be done in your hospital room, before you are taken to the operating room, and before you are given the anesthetic pre-medications that dim your alertness of mind."

Source -- Khan, MA (2002). Ankylosing Spondylitis: The Facts (The Facts Series). New York: Oxford University Press Inc.