The slope of the learning curve in 600 consecutive endoscopic transsphenoidal pituitary surgeries

Background Endonasal endoscopic transsphenoidal surgery (EETS) for pituitary adenoma has become a mainstay of treatment over the last two decades and it is generally accepted that once this learning curve is achieved, a plateau is reached with little incremental improvement. Objective The objective of this study was to assess the slope of the learning curve over a long period of time for a variety of outcomes measures. Methods We examined outcomes and complications in a consecutive series of 600 EETS for pituitary adenoma grouped into quartiles based on date of surgery. Results GTR significantly increased across quartiles from 55 to 79% in the last quartile (p < 0.005). The rate of intraoperative CSF leak significantly decreased from 60% in the first quartile to 33% in the last quartile and the rate of lumbar drain placement from 28% in the first quartile to 6% in the last quartile (p < 0.005). Hormonal remission for secreting adenomas increased from 68% in the first quartile to 90% in the last quartile (p < 0.05). The rate of post-operative CSF leak trended lower (3% in first quartile to 0.7% in last two quartiles). The greatest improvement in outcome occurred between the first and second quartiles (19.9%), but persistent improvement occurred between the second and third (6.7%) and third and fourth quartiles (8.0%). Conclusion Although the slope of the learning curve is steeper earlier in a surgeon's experience, the slope does not plateau and continues to increase even over more than a decade.