Risk Factors and Outcomes for Conversion to Laparotomy of Laparoscopic Hysterectomy in Benign Gynecology
The predicted conversion rate for robotic compared with traditional laparoscopy was both statistically significant and clinically meaningful. The regression analyses did adjust for specimen weight and moderate-to-severe adhesive disease, which makes the result even more significant.
The key thing I would have wanted to see is a stratified analysis by specimen weight. In other words, for the smallest uteri, with no adhesive disease, does robotic surgery still have a significantly lower conversion rate? The problem right now is that the robot is being used widely, even in cases in which the uterus is small and there is no adhesive disease. The authors tested for an interaction between surgeon volume and surgical approach. I would have loved to see the interaction between specimen weight and surgical approach in terms of the risk of conversion. The difference in predicted conversion rate by surgeon volume (1.4% compared with 2.25%) was not clinically meaningful in my opinion.
In terms of statistical methodology, the authors accounted for clustering at the level of the hospital but not at the level of the surgeon. This could be problematic. Patients operated on by the same surgeon are going to have outcomes that are correlated. Adjusting for clustering at the level of the surgeon is therefore critical. A hierarchical–multilevel model should have been used with adjustment for clustering at the level of both the hospital and the surgeon. See the Methods section in the article by Welk et al2 for comparison.