Novel Scoring System Predicts Complications Post Spinal Fusion
Lead author Jacqueline L. Munch, MD comments about this clinical study
A novel simple-to-use scoring system that can postoperatively predict which patients are at a higher risk for major complications from spinal fusion has been published in a recent issue of The Spine Journal.
According to Jacqueline L. Munch, MD and colleagues from the Department of Orthopaedics and Rehabilitation at Oregon Health and Science University, the scoring system is based on “four perioperative parameters that are most closely associated with the invasiveness of the surgical intervention.” These include the number of levels fused, operative time, volume of intraoperative fluids administered, and estimated blood loss (EBL). It is these four variables and the American Society of Anesthesiologists’ (ASA) scoring system that are used to predict the risk of complications.
The ability to postoperatively predict those patients at increased risk for complications will help guide the care team in postoperative patient management. According to the authors they, “assign a hospitalist to those patients at highest risk. The goal is to optimize medical management after surgery, and intervene before complications occur.” Blood sugar and fluid control are the most commonly used interventions by the hospitalist.
The Need for a Scoring System
Currently, postoperative management of spinal fusion patients is made by the surgery and anesthesiology teams, but it is primarily based on anecdotal evidence. According to the authors, “The rate of thoracic, lumbar and thoracolumbar fusion surgery has been increasing rapidly in the US population, with the fastest increase occurring among older patients.” It is in this over 60-age group that there is a higher risk of postoperative complications.
The only scoring system that was available to predict complications in spine surgery patients was the Spine Surgical Invasiveness Index. With this system, “the authors demonstrated that EBL and operative time were predictive of postoperative infections in spine surgery. However, this scoring system was not predictive of overall medical complication rates,” the authors commented.
The authors retrospectively reviewed the records of 269 men and 440 women who had undergone elective thoracic, lumbar or thoracolumbar fusion between 2007 and 2011. Major medical complications were obtained for a 30-day postoperative period. Associations between variables (both routine and those that represent the invasiveness of the surgery) as well as major complications were analyzed.
The major medical complication rate was 16.7% (eg, renal failure, pulmonary embolism, arrhythmia). Routine variables, including bone mass index (BMI), vital signs, smoking status, gender, and status as a revision fusion was not significantly associated with major complications. Risk categorization was based on the ASA scoring system, with ASA 3-4 defined as high risk and ASA 1-2 as low risk. The complication rate for a patient with an ASA of 3-4 was 20.6% compared to 7% for patients with an ASA of 1-2.
“Patients with ASA scores of 3-4 had immediate, statistically significant increases in complication rates as the fusion levels, operative time, volume of fluid and EBL increased, whereas patients with ASA scores of 1-2 had complication rates that remained relatively low irrespective of these perioperative levels,” the authors said.
A scoring system based on the number of fusion levels, operative time, volume of fluid and EBL was generated. For patients at high risk (ASA 3-4), these four variables correlated with major medical complications almost perfectly (r=.999, P<.0001), and for patients at low risk (ASA 1-2) there was also a positive predictive value (r=.92).
The scoring system proposed by the authors can only be used postoperatively. However, “the ideal scenario would be a tool that could identify patients at risk prior to surgery,” the editors said. Additionally, “translation of these findings is limited to patients with severe medical comorbidities undergoing elective thoracic and lumbar procedures. This may impair the capacity for broad generalization to patients who undergo spine surgical procedures in general.”
Summation and Future Directions
“Our scoring system is simple and easily used at the bedside, and it provides a clear definition of the concept of multilevel fusion as a risk factor for complications. We believe that the scoring system can provide some estimation of the risk of the surgery based on the number of levels and estimation of length of surgery, blood loss and volume of intraoperative fluids,” the authors concluded.
The authors will continue their research by prospectively examining the ability of their system to predict perioperative morbidity and mortality.