LAUSR

C TO THE EDITOR: Letter to Editor About the Article ‘‘Hills J, Sivaganesan A, Khan I, et al. Causes and Timing of Unplanned 90-day Readmissions Following Spine Surgery. Spine (Phila Pa 1976) 2018;43:991-8.’’ e read with great interest the article of Hills 1 W et al in a recent issue of the journal. The authors performed a retrospective cohort study on 2761 patients undergoing spine surgery and concluded that nearly half of all unplanned 90-day readmissions were owing to pain and medical complications and occurred with a median time of 6and12days, respectively.Theauthors shouldbecongratulated for performing a well-designed study in an important topic (e.g., hospital readmissions) in patients undergoing surgery. In addition, the current emphasis on the use of multimodal analgesic strategies to enhance recovery across many surgical procedures makes the topic timely in perioperative medicine. Although the study of Hills et al was well-conducted, there are some concerns regarding the study that need to be clarified to determine the validity of the results. First, the authors reported 156 unplanned admissions. However, they investigated>15 predictor variables in their analysis,which can lead to substantial overfitting of the model. The authors did not provide any formal explanation for this potential problem. Secondly, there is no analysis of postoperative analgesic strategies. This may be the main factor leading to pain related readmissions. Lastly, education and health literacy may have an important effect on postoperative analgesic adherence and has been associated with hospital readmissions in other clinical settings. Nonetheless, these variables were not evaluated in the model.