Dear Editor,

We read with great interest the article of Saku and colleagues in a recent issue of the journal [1]. The authors performed a retrospective cohort study on 861 patients undergoing total knee arthroplasty and concluded that knee pain was the second most common reason for re-admission accounting for 14.1% of total re-admissions. The authors should be congratulated for performing a well-designed study in an important topic (e.g., hospital re-admissions) in patients undergoing surgery [2, 3]. In addition, the current emphasis on use of multimodal analgesic strategies to enhance recovery across many surgical procedures makes the topic timely in peri-operative medicine [4, 5].

Although the study of Saku et al. was well conducted, there are some questions regarding the study that need to be clarified by the authors. First, the authors’ data revealed 116 unplanned re-admissions but they examined more than 20 predictor variables in their analysis leading to a substantial overfitting of the model. The authors did not provide any explanation or evaluation for this problem. Secondly, there is no analysis of post-operative analgesic strategies which may be the main factor leading to pain-related re-admissions and a significant confounder for the study results. Lastly, education and health literacy may have also been linked to hospital re-admissions in other clinical settings [6]. Nonetheless, these variables were not evaluated in the model.

We would welcome some comments to address the aforementioned issues as they were not discussed by the authors. This would help to further validate the findings of this important clinical study.