29th September 2020

An active 65-year-old male with a past medical history of ankylosing spondylitis

An active 65-year-old male with a past medical history of ankylosing spondylitis is undergoing a total hip replacement for osteoarthritis. The anaesthetist experiences difficulties inserting the needle to administer a spinal anaesthetic for post-operative analgesia because of which feature on x-ray?

Select the SINGLE most appropriate option from the list above.