Accuracy of SPECT Scanning in Diagnosing Pseudarthrosis: A Prospective Study

Study Design
This study examined the single photon emission computed tomography (SPECT) scans of 38 patients prior to undergoing surgical exploration of their fusion mass for suspected pseudarthrosis or in conjunction with instrumentation removal. Surgical findings were compared with the radiologists findings in order to determine the efficacy of SPECT in diagnosing pseudoarthrosis.

Objectives
The present study attempted to analyze the efficacy of SPECT in diagnosing pseudarthrosis after fusion utilizing surgical exploration as the gold standard.

Summary of Background Data
Radiographic determination of pseudarthrosis has been difficult following 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.

Methods
Thirty-eight patients (mean age = 42.8, 21 males/17 females, 35 of 38 with instrumentation) underwent SPECT scans prior to surgical exploration of their fusion mass for suspected pseudarthrosis 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 (9 to 120 months). All surgical findings were recorded with regard to solidity of the fusion and the level of the possible pseudarthrosis. All SPECT scans were read by an independent nuclear radiologist at a time after surgery who had not read their SPECT scans prior to surgery and who did not know the results of exploration. Results of the radiologist's reading were then compared to surgical exploration findings and sensitivity and specificity was calculated.

Results
There were 24 solid fusions and 14 pseudarthroses. SPECT scan correctly identified 7 of the 14 pseudarthroses, 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 2 pseudarthrosis patients in the 3 patients who had no instrumentation.

Conclusion
This study demonstrates that SPECT scanning alone is inaccurate in diagnosing pseudarthrosis when utilizing 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 pseudarthrosis. We cannot define the accuracy of SPECT scanning used together with CT scans, plain films or other radiographic modalities in the diagnosis of pseudarthrosis.

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© 2002, Rothman Institute.
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