ACCURACY OF SPECT SCANNING IN DIAGNOSING PSEUDARTHROSIS - A PROSPECTIVE-STUDY

The present study attempted to analyze the efficacy of single photon e mission computed tomography (SPECT) in diagnosing pseudoarthrosis afte r fusion using surgical exploration as the gold standard. This study e xamined the SPECT scans of 38 patients before they underwent surgical exploration of their fusion mass for suspected pseudoarthrosis or in c onjunction with instrumentation removal. Surgical findings were compar ed with the radiologists' findings to determine the efficacy of SPECT in diagnosing pseudoarthrosis. Radiographic determination of pseudoart hrosis has been difficult after attempted fusion of the spine. Multipl e radiographic modalities have been touted as accurate depicters of th e failure of spinal fusion. However, no method has been found to be hi ghly 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 susp ected pseudoarthrosis or in conjunction with instrumentation removal a s part of this prospective study. The average interval from their fusi on procedure until their SPECT scan was 23.9 months (range, 9-120 mont hs). All surgical findings were recorded with regard to solidity of th e fusion and the level of the possible pseudoarthrosis. All SPECT scan s were read at a time after surgery by an independent nuclear radiolog ist 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 ps eudoarthroses. SPECT scans correctly identified 7 of the 14 pseudoarth roses and 14 of the 24 solid fusions. This represents a sensitivity of 0.50 and a specificity of 0.58. SPECT scanning correctly diagnosed th e one solid fusion and two pseudoarthrosis patients in the three patie nts who had no instrumentation. This study demonstrates that SPECT sca nning alone is inaccurate in diagnosing pseudoarthrosis when using sur gical exploration as the gold standard. Given recent pressures for cos t containment, we cannot recommend SPECT scanning as a routine modalit y for use in the diagnosis of pseudoarthrosis. We cannot define the ac curacy of SPECT scanning used together with computed tomography scans, plain films, or other radiographic modalities in the diagnosis of pse udoarthrosis.