Analysis of factors influencing ligamentum flavum thickness in lumbar spine - A radiological study of 1070 disc levels in 214 patients

Abstract Objective The pathomechanism and factors influencing hypertrophy of the Ligamentum flavum in the lumbar spine still requires a confident specificity. We aimed to analyse the association between various factors and Ligamentum Flavum Thickness (LFT) and also to investigate the major contributor for Ligamentum Flavum Hypertrophy (LFH) at various levels in the lumbar spine. Patients and methods The following were evaluated at L1-L2,L2-L3,L3-L4,L4-L5 and L5-S1 levels in MRI of 1070 lumbar disc levels of 214 subjects: Pfirrmann’s grade of the disc, anterior and posterior disc height, disc volume, facet tropism and LFT. LFT > 0.4 cm was considered as hypertrophy.Correlation between LFT and other parameters was done and values with p  Results 112 male and 102 female were included. There was an increase in the anterior disc height (0.98 cm to 1.50 cm), posterior disc height (0.84 cm to 0.96 cm), disc volume (7.17cm 3 to 14.6cm 3 ), facetal angle and LFT on both sides from L1-2 to L5-S1 levels. Highest frequency of LFT was seen at L4-5.Pfirrmann’s grade of the disc and anterior disc height had a statistically significant positive correlation with LFT at L1-L2,L2-L3,L3-L4,L4-L5 levels whereas facet tropism was strongly associated with LFT at L5-S1 level. Conclusion Higher Pfirrmann’s grade and decreased anterior disc height can lead to ligamentum flavum hypertrophy at L1-L2, L2-L3,L3-L4,L4-L5 levels.Whereas at L5-S1 level, it is the presence of facet tropism which can cause LFH. Hence, patients with the presence of above mentioned factors at those respective levels have higher preponderance to develop Lumbar canal stenosis.