• Yutaka Yabe, Yoshihiro Hagiwara, Akira Ando, Masahiro Tsuchiya, Takashi Minowa, Taro Takemura, Masahito Honda, Kouki Hatori, Kazuaki Sonofuchi, Kenji Kanazawa, Masashi Koide, Takuya Sekiguchi, and Eiji Itoi.
• *Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan †Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan ‡Nanotechnology Innovation Station, National Institute for Materials Science, Tsukuba, Japan §Department of Otrhopaedic Surgery, Takeda General Hospital, Aizuwakamatsu, Japan; and ¶Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
• Spine. 2015 Apr 1; 40 (7): 429-35.

Study DesignA histological, biological, and immunohisto-chemical study of human lumbar ligamentum flavum.ObjectiveTo analyze changes in the hypertrophied ligamentum flavum and clarify their etiology.Summary Of Background DataHypertrophy of the ligamentum flavum has been considered a major contributor to the development of lumbar spinal canal stenosis (LSCS). Although previous studies have reported some factors related to ligamentum flavum hypertrophy, its etiology is still unclear.MethodsLigamentum flavum samples were collected from 20 patients with LSCS (LSCS group) and 10 patients with lumbar disc herniation (LDH group) as a control. The thickness of the ligamentum flavum was measured histologically. The amounts of elastic fibers and proteoglycans were assessed by Elastica-Masson staining and alcian blue staining, respectively. Gene and protein expressions related to fibrosis, inflammation, and chondrogenesis were analyzed by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. The total genes of the 2 groups were compared by DNA microarray analysis.ResultsThe ligamentum flavum was significantly thicker in the LSCS group, which had a smaller amount of elastic fibers and a larger amount of proteoglycans. The gene expression related to fibrosis was significantly higher in the LSCS group; however, the immunoreactivities of collagen types I and III were weaker on the dorsal side of the ligamentum flavum in the LSCS group. The gene expression related to chondrogenesis and proteoglycan synthesis was significantly higher in the LSCS group. There was no significant difference in the gene expression related to inflammation between the 2 groups.ConclusionSynthesis of the collagenous fibers and degradation of the elastic and collagenous fibers are both accelerated in the ligamentum flavum of patient with LSCS, which may be the reason for hypertrophy of the tissue. In addition, chondrogenesis and proteoglycan synthesis may have critical roles in the pathogenesis of the ligamentum flavum hypertrophy.Level Of Evidence5.

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