Validation of Training Levels in Endoscopic Endonasal Surgery of the Skull Base

Background A five-level training program was first proposed 10 years ago for skull base surgeons learning endoscopic endonasal surgery (EES) of the skull base. Levels were based on the complexity of anatomy, proximity, and risk of injury to major neurovascular structures, intradural dissection, technical difficulty, and vascularity of tumors.

Methods A three-phase validation concept is proposed: (1) face validity (the classification is related to clinically significant elements), (2) construct validity (the classification predicts the outcome), and (3) interrater reliability (the classification applies to other surgical teams). Consecutive cases over a 1-year time span were retrospectively classified according to the previously described training levels. Primary outcome measures included major and minor complications, estimated blood loss (EBL), duration of surgery (DOS), length of hospitalization (LOH), and readmission rates (RR). Two surgical teams at the same institution were compared. One-way ANOVA tests were performed for parametric data analysis, Kruskal–Wallis tests for nonparametric data analysis, and chi-square test for categorical data analysis.

Results A total of 210 consecutive cases from April 2016 to April 2017 were analyzed. The distribution of cases for each category was: level II—56, level III—69, level IV—77, level V—7. Level I was omitted as it does not include skull base surgery. Statistically significant differences were found between levels III and IV for the rates of minor and major complications (including cerebrospinal fluid leaks), EBL, and DOS. When comparing levels IV and V, there was also a statistical difference in the rate of major complications. Face validity was assessed by citation analysis. With over 134 citations, citation analysis confirmed landmark status of this article. As for interrater reliability, there was no difference between the two teams of surgeons for minor and major complication rates.

Conclusion This study provides a three-phase validation of training levels for EES. Factors that determine training levels should be considered as part of surgical planning. Adoption of a progressive systematic approach to the learning curve for EES from less complex to advanced procedures is expected to minimize the risks of EES while surgical teams gain experience.