Pathomehcanism of lumbar ligamentum flavum hypertrophy

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The pathomechanism of hypertrophy of ligamentum flavum (LF) is still unknown. We hypothesized that the mechanism would be similar to that in the hypertrophic scar formation during the would repair of skin. The pathology is considered to be fibro-proliferative disorder (FPD). To confirm the hypothesis, we have investigated the similarity of the hypertrophy of LF and hypertrophic scar. Hypertrophied LF samples were taken during the lumbardecompression surgery. Masson Trichlome (MT) and Elastica van Gieson (EVG) stain were uded to understand the scar and fibrosis. The similarity of FPD was investigated using the immunohistochemistry of type 1 and 3 collagen and alfa-smooth muscle antigen (αSMA). In the hypertrophied LF, elastic fiber was stained sparse, especially along the dorsal aspect in LF. Instead, scar and fibroscic tissue was confirmed in the LF. At the scarring site, type 1 and 3 collagen was stained. The αSMA was also confirmed to be stained. Thus, hypertrophy of LF would be a type of the fibro-proliferative disorder. The other major matrix of the normal LF is type 1 collagen. We evaluated the bad crosslink in collagen named Pentocidine, which reduces the ligament elasticity . We confirmed the existence of the pentocidine in LF, especially at the cite where type 1 collagen showed abundant production.