187. Compared to gold standard bone SPECT/CT showed superior accuracy in detecting pseudarthrosis

BACKGROUND CONTEXT Pseudarthrosis remains the primary cause of persistent pain postoperatively after spinal fusion surgery, leading to failed back surgery syndrome. The utility of the integrated single-photon emission computed tomography and computed tomography (SPECT/CT) in a bone scan as a problem-solving tool in evaluating patients with suspected pseudarthrosis, hardware failure and adjacent level disease has been previously reported. A number of studies have been done showing its benefits and limitations when compared to other imaging techniques. Direct comparison against the gold standard of surgical pseudarthrosis confirmation is limited. PURPOSE The purpose of this study is to evaluate the diagnostic accuracy of SPECT/CT, computed tomography (CT) and magnetic resonance imaging (MRI) scans in preoperatively identifying pseudarthrosis with verification by intraoperative findings. STUDY DESIGN/SETTING Retrospective study. PATIENT SAMPLE Patients undergoing revision spinal surgery. OUTCOME MEASURES Imaging comparison to gold standard. METHODS After obtaining IRB approval, a retrospective study of patients who underwent revision spinal fusion was completed. The surgeries were performed by a single orthopedic spine surgeon over a 12-month period. Patients included in the study had SPECT/CT imaging done prior to surgery, and had either MRI or CT scan or both. All available preoperative imaging results (SPECT/CT, CT and MRI) and operative reports were collected, verified and compared. Estimates of sensitivity, specificity, likelihood ratios (LRs), positive predictive value (PPV) and negative predictive value (NPV) were all calculated to evaluate the diagnostic accuracy. RESULTS A total of 60 surgical patients (62% female, mean age 58 years), including 19 cervical fusion (32%), five thoracolumbar fusion (8%) and 36 lumbar fusion (60%), were included in this series. Prior to spinal surgery, average time to imaging of 60 patients who underwent SPECT/CT, 31 patients who underwent CT, and 33 patients who underwent MRI was around 5 months, respectively. Results of diagnostic accuracy show that when compared to lower sensitivity studies like CT (11%) and MRI (6%), SPECT/CT sensitivity was high at 91% (95% CI 75-98%) leading a significant negative likelihood ratio at -LR 0.1 (95% CI 0.04-0.36) and a PPV of 83% (95% CI 70-91%); specificity was moderate at 79% (95% CI 59-92%) with a moderate positive likelihood ratio of +LR 4 (95% CI 2-9) and a NPV of 88% (95% CI 71-96%). CONCLUSIONS SPECT/CT scan was found to demonstrate excellent criterion validity to rule-out a diagnosis of pseudarthrosis when a negative result was observed; however, further validation is warranted. DISCUSSION Pseudarthrosis can be challenging to diagnose as it can also occur with other postoperative complications such as adjacent level disease and/or hardware failure, SPECT/CT scan should be integrated into routine clinical practice as a diagnostic tool in patients with persistent postoperative pain. A negative SPECT-CT virtually rules out pseudarthrosis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.