Opacity and Lucency Sign of the Seventh Lumbar Vertebra in Dogs

Abstract

A curvilinear opacity of the seventh vertebral arch and an adjacent focal lucency of the seventh lumbar vertebral body were incidentally noted in routine radiographs. The aim of this study was to analyze this radiographic absorption pattern using a sample of 51 dogs. Images of the bony surface of three macerated lumbosacral junctions were compared to their laterolateral radiographs and computed tomographic (CT) scans. Additional 48 lateral radiographic projections were reviewed for presence or absence of L7 opacity and lucency, length of the L6 and L7 vertebral bodies, vertebral disc disease, osteochondrosis, or spondylosis. Retrieved data were compiled and statistically analyzed. Radiographs and CT scans of the macerated bones revealed that the L7 pedicle had thickened layers of compact bone and the adjacent vertebral notch varying depth and extension. Superimposition of the pedicle on the vertebral body resulted in a curvilinear opacity (L7 opacity), the vertebral notch caused the focal lucency (L7 lucency). These findings were present in 69% of the reviewed radiographs and were found to be significantly associated with L6-L7 length ratios of less than 0.86 (P = 0.003). It is hypothesized that the changes correspond with normal anatomic morphology of the seventh lumbar vertebra plus adaptive bone remodelling. The importance of this study is that it could help avoid misinterpretation of this appearance as a pathologic condition.