Spinal Metastasis Surgery: A Proposal for a Predictive Model of Morbidity and Mortality

Objective To develop a predictive model of early postoperative morbidity and mortality with the purpose of assisting in the selection of the candidates for spinal metastasis surgery. Methods A retrospective analysis of consecutive patients operated for metastatic spinal disease. The possible prognostic preoperative characteristics were gender, age, comorbidities, tumor growth rate, and leukocyte and lymphocyte count in the peripheral blood. The postoperative outcomes were 30-day mortality, 90-day mortality and presence of complications. A predictive model was developed based on factors independently associated with these three outcomes. The final model was then tested for the tendency to predict adverse events, discrimination capacity and calibration. Results A total of 205 patients were surgically treated between 2002 and 2015. The rates of the 30-day mortality, 90-day mortality and presence of complications were of 17%, 42% and 31% respectively. The factors independently associated with these three outcomes, which constituted the predictive model, were presence of comorbidities, no slow-growing primary tumor, and lymphocyte count below 1,000 cells/µL. Exposure to none, one, two or three factors was the criterion for the definition of the following categories of the predictive model: low, moderate, high and extreme risk respectively. Comparing the risk categories, there was a progressive increase in the occurrence of outcomes, following a linear trend. The discrimination capacity was of 72%, 73% and 70% for 30-day mortality, 90-day mortality and complications respectively. No lack of calibration occurred. Conclusion The predictive model estimates morbidity and mortality after spinal metastasis surgery and hierarchizes risks as low, moderate, high and extreme.