To delineate the optimal CT parameters for determining fusion versus pseudarthosis after attempted lumbar fusion.
Blinded CT assessment with cadaveric specimen as a gold standard.
A human cadaveric spine specimen with a T10 to S1 thoracolumbar posterolateral fusion augmented by instrumentation and anterior lumbar interbody fusions was used as a gold standard. Two experienced spine surgeons and one musculoskeletal radiologist—all blinded to the pathology results—assessed a series of CT scans of the specimen, each CT using one of six predefined sets of parameters.
Predictive values and sensitivity generally improved with decreasing slice thickness and slice spacing, but only modestly. All sets of parameters had higher negative predictive value (NPV) than positive predictive value (PPV). Computed tomographic parameters of 0.9-mm thick sections with 50 % overlap showed the highest PPV and NPV, where NPV was 90, but PPV was only 59.
In this study, using the best widely available CT technologies and the ideal gold standard, thin-cut CT remained less than ideal for the assessment of lumbar arthrodesis/pseudarthrosis. Tuning slice thickness and slice spacing down generally improves detail, but marginally. We have successfully defined “optimal” as “best available,” but “optimal” as “nearly perfect” awaits further technological advances.