Accuracy of SPECT scanning in diagnosing pseudoarthrosis: a prospective study

The present study attempted to analyze the efficacy of single photon emission computed tomography (SPECT) in diagnosing pseudoarthrosis after fusion using surgical exploration as the gold standard. This study examined the SPECT scans of 38 patients before they underwent surgical exploration of their fusion mass for suspected pseudoarthrosis or in conjunction with instrumentation removal. Surgical findings were compared with the radiologists' findings to determine the efficacy of SPECT in diagnosing pseudoarthrosis. Radiographic determination of pseudoarthrosis has been difficult after attempted fusion of the spine. Multiple radiographic modalities have been touted as accurate depicters of the failure of spinal fusion. However, no method has been found to be highly accurate in the clinical setting. Thirty-eight patients (mean age = 42.8, 21 males/17 females, 35 of 38 with instrumentation) underwent SPECT scans before surgical exploration of their fusion mass for suspected pseudoarthrosis or in conjunction with instrumentation removal as part of this prospective study. The average interval from their fusion procedure until their SPECT scan was 23.9 months (range, 9-120 months). All surgical findings were recorded with regard to solidity of the fusion and the level of the possible pseudoarthrosis. All SPECT scans were read at a time after surgery by an independent nuclear radiologist who had not read their SPECT scans before surgery and who did not know the results of exploration. Results of the radiologist's reading were then compared with surgical exploration findings, and sensitivity and specificity was calculated. There were 24 solid fusions and 14 pseudoarthroses. SPECT scans correctly identified 7 of the 14 pseudoarthroses and 14 of the 24 solid fusions. This represents a sensitivity of 0.50 and a specificity of 0.58. SPECT scanning correctly diagnosed the one solid fusion and two pseudoarthrosis patients in the three patients who had no instrumentation. This study demonstrates that SPECT scanning alone is inaccurate in diagnosing pseudoarthrosis when using surgical exploration as the gold standard. Given recent pressures for cost containment, we cannot recommend SPECT scanning as a routine modality for use in the diagnosis of pseudoarthrosis. We cannot define the accuracy of SPECT scanning used together with computed tomography scans, plain films, or other radiographic modalities in the diagnosis of pseudoarthrosis.