Sentence:  Although this technique avoids the retrograde dissection of the facial nerve through the geniculate ganglion and labyrinthine segment, the obvious disadvantage of <WSD>bluelining</WSD> is that it carries a risk of fenestrating the superior semicircular canal. 
Meaning of the word marked with <WSD> tags:  To mark on a patient's body where the surgical incision is to be made.