The value of scintigraphy in the diagnosis of pseudarthrosis after spinal fusion surgery

The utility of planar bone scintigraphy was evaluated for discerning bony u nion after spinal fusion surgery, especially in cases of clinically and rad iologically suggested pseudarthrosis. Between 1991 and 1996, the authors pe rformed bone scintigraphy on 42 patients (21 women, 21 men; mean age, 42 ye ars) after spinal fusion surgery (32 posterolateral, 10 combined) and just before their admission to the hospital for material removal. The fusions co nsisted of 29 lumbosacral, 6 thoracolumbar, 3 lumbar, 2 thoracolumbosacral, 1 thoracic, and 1 cervical. The mean fusion spanned four segments, and the mean time between spinal fusion and material removal was 27 months. The sc intigraphy was performed using the tracer Tc-99m. Based on the scintigraphy data, the radiologist suspected pseudarthrosis in five patients (12%), and the condition was confirmed in four patients during operation (10%), two d iagnosed and two undiagnosed. The accuracy of the method was 88%; sensitivi ty, 50%, specificity, 93%; positive predictive value, 40%; and negative pre dictive value, 95%. The sensitivity and positive predictive value of bone s cintigraphy are low for possible instability after spinal fusion. The metho d is not sufficient to reliably diagnose pseudarthrosis after spondylodesis .