5-Year longitudinal magnetic resonance imaging follow-up of a population-based cohort of subjects with ossified yellow ligament: a natural history study

Abstract

INTRODUCTION: Ossified yellow ligament (OYL) causes the majority of thoracic myelopathy. This study presents longitudinal follow-up of these individuals to assess changes related to disease progression and risk factors for such progression. METHODS: In a population-based study of 1864 southern Chinese volunteers using magnetic resonance imaging (MRI), 114 individuals were identified to have OYL. The MRI parameters assessed included the size of OYL, levels of involvement, OYL morphology, whether the OYL crossed midsagittal region, and the presence of degenerated discs. Both baseline and 5-year follow-up MRIs were read by 2 observers blinded to clinical information and any differences were settled by consensus. RESULTS: Size progression was defined as bigger OYL size in the follow-up MRI than that in baseline MRI. In all, 70% T9/10 and 62% T10/11 OYLs had size progression (p<0.05). Majority of de-novo OYL (new OYL formed only in the follow-up scan) developed in T8/9 to T11/12. They were observed in 70% of segments who had body mass index of 30 to 40 kg/m2 (p=0.02), otherwise no other risk factors could be found. DISCUSSION: This is the first and only population-based series addressing the natural history of OYL. Myelopathy commonly occurs in the lower thoracic region and this study showed that most of the lower thoracic OYLs progressed in size. Knowing the natural history of OYL at 5-year follow-up, preventive measures such as weight reduction, close monitoring for myelopathy development, and perhaps early operation for lower thoracic OYL may be necessary.