While the question is of utmost importance and can have major impacts on spine surgery practice, there are many methodological concerns that should be made clear. First, the definition of outpatient setting is not fully described either in paper nor in NSQIP’s guide [2]. They have mentioned that they used NSQIP’s variables as-is, which is ambiguous. Second, the conclusion cannot be fully drawn by what has been performed as there are desirable outcomes (i.e., stability, cervicalgia, etc.) and overall cost-benefit measures which are not quantified. There are many baseline variables that differ substantially between two groups of study. It might be deferred as multi-variate logistic regression would capture the confounding effects of these factors, but the fact is that two groups have such difference, multiple regression analysis cannot account for the confounding factors. For such heterogeneous samples with large sample reserve available, doing propensity matching followed by stepwise regression model creation is more promising, as carried out on same or similar databases several times before [3-6]. In addition, there are some other variables that ideally are required to be in the models (yet NSQIP may not provide them) and should be considered in real world decision making. Variables like the experience of surgeon, insurance coverage, severity of disease, presence of deformity and performance of alignment surgery, and neurological involvement. Another inherent limitation of NSQIP is that not every institute in United States is a partner and there is a leaning toward larger and wealthier academic centers that might hardly be generalizable to whole population and every setting [7]. Also, analytical efforts in disease severity and number of levels subgroups may have more practical results for our daily practice.

This is an impressive piece of work with immersive impact. However, the impact of this article is limited due to the limitations mentioned above, and broad extrapolations of the data should be limited. The above comments may mildly alter estimates, but most likely the main findings will remain the same. Future works to assess early discharge and ambulation may also point out the aim of this study in a more practical way.