Effect of psoas muscle index on early postoperative outcomes in surgically treated spinal tumours in an Asian population

•Psoas Muscle Index (PMI) is a measure of sarcopenia and has been shown to be associated with post-operative outcomes in degenerative spinal surgery.•We investigated if there was an association between PMI and post-operative outcomes in patients undergoing surgery for spinal tumours.•Patients with lower PMI values were found to have significantly longer lengths of stays whilst there was no significant association with complications.•PMI values can be used to risk stratify patients undergoing surgery for spinal tumours. Sarcopenia has been purported to be a pre-operative risk factor that affects patient outcomes in oncological surgery, but no study as of yet has investigated the effect of sarcopenia in patients with spinal tumours. Psoas muscle measurements, including the psoas muscle index (PMI), are an objective way to determine sarcopenia. We investigated if PMI could predict post-operative outcomes (length of hospital stay and post-operative complications) in surgically treated spinal tumour patients in a multi-ethnic Asian population. We conducted a retrospective cohort study of patients with spinal tumours who underwent surgery at our tertiary institution from January 2016 to January 2020. PMI was measured on T2-weighted MRI sequences, at the middle of the L3 vertebral body and measurements were collected by 2 independent raters. The primary outcome was length of hospital stay (LOS), and the secondary outcome was post-operative complications. ROC curve was used to attain the cut-off value for PMI and the population was then stratified into 2 groups; sarcopenic if PMI was less than 1.22 and non-sarcopenic if the PMI value was more than or equal to 1.22. Multivariable linear regression was used for LOS, while multivariate logistic regression was used for complications. 57 patients were included with a mean length of stay of 17.8 days (SD 25.1) and the total number of patients with complications were 20 (35.1 %). Mean LOS was significantly higher in the sarcopenic group compared to the non-sarcopenic group. Univariate analysis confirmed the association of lower psoas muscle index corresponding with longer lengths of stay and this was corroborated in a multivariable linear regression model. There were no significant associations between PMI and postoperative complications. Lower PMI values were significantly associated with a longer LOS. PMI may be warranted for risk stratifying Asian spinal tumour patients undergoing surgery.