Facet joint degeneration adversely affects ultrasound imaging of the lumbar spine

Aim: Ultrasound of neuraxis can be used to identify the best possible inter-spinous space to perform neuraxial block. The aim of this study was to assess the anatomical correlation between neuraxial ultrasound and magnetic resonance imaging (MRI). Material and method: Twenty-one patients who underwent MRI of the lumbar spine had ultrasound of lumbar neuraxis performed by an experienced operator. Each lumbar interspinous space was graded on ultrasound as good [posterior complex (ligamentum flavum and duramater) and anterior complex (posterior longitudinal ligament) visible], intermediate (either anterior complex or posterior complex visible) or poor (both anterior complex and posterior complex not visible) in both the transverse median (TM) and paramedian sagittal oblique (PSO) plane. Pre-determined MRI parameters were measured by a radiologist blinded to sonographic findings at each inter-spinal level. Results: Seventy-eight lumbar interspinous spaces were evaluated. There was a significant association (p<0.004) between the facet joint degeneration on MRI and the poor ultrasound view in the transverse median (TM) group. The odds of obtaining a poor view in TM plane was 7 times higher (95% CI 1.7-28.9, p=0.007) in the presence of facet joint degeneration. None of the other variables had a significant association with a poor neuraxial view in the TM plane. Poor views in the parasagittal oblique (PSO) plane did not correlate with any of the variables measured on MRI. Conclusion: Facet joint degeneration is a major contributing factor to poor neuraxial ultrasound views in the TM plane.