Dorsal Spinal Ligamentum Flavum Thickening: A Magnetic Resonance Imaging Study

STUDY DESIGN: A retrospective radiological study of the ligamentum flavum (LF). PURPOSE: We determined the relationship of dorsal spinal LF thickening with age and sex using magnetic resonance imaging (MRI). We also determined whether LF thickening has a predominant tendency to occur at a specific dorsal level and on a specific side. OVERVIEW OF LITERATURE: Many researchers have studied LF thickness at dorsal levels in patients with compressive myelopathy. However, there is a dearth of literature pertaining to the study of dorsal LF thickness in patients without myelopathy. METHODS: LF thickness was measured at dorsal levels from T1 to T12 on both sides using MRI in 100 individuals. The patients were divided into three groups based on age: 20 to 40, 41 to 60, and >60 years. On axial T2-weighted imaging at the mid-disc level, LF thickness was measured perpendicular to the lamina border, either at half the length of LF or at maximum thickness, whichever was greater. RESULTS: We found that LF thickness does not increase significantly with increasing age and there was no significant disparity in LF thickness between the sides and sexes. We also found that there was a significant increase in LF thickness at the T10–T11 level (mean value, 3.27±0.94 mm). CONCLUSIONS: LF thickness does not appear to have any side/sex dominance. LF thickening has a predominant tendency to occur specifically at the T10–T11 level. This may be due to maximum tensile strength and mobility at this level. Because there is an increased tendency for LF thickening at the T10–T11 level, this may be used as a reference point for counting the vertebral levels.