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Spondylolisthesis is the forward displacement of a vertebra, especially the fifth lumbar vertebra, most commonly occurring after a fracture. Backward displacement is referred to as retrolisthesis. The variant "listhesis," resulting from division of this compound word, is sometimes applied in conjunction with scoliosis. These "slips" occur most commonly in the lumbar spine. Spondylolysis (a defect or fracture of the pars interarticularis of the vertebral arch) is the most common cause of spondylolisthesis, which should not be confused with a slipped disc, in which one of the spinal discs in between the vertebrae has ruptured. A ''hangman's fracture'' is a specific type of spondylolisthesis where the second cervical vertebra (C2) is displaced anteriorly relative to the C3 vertebra due to fractures of the C2 vertebra's pedicles. ==Classification== Spondylolisthesis is categorized into five types:〔(【引用サイトリンク】url=http://orthoinfo.aaos.org/topic.cfm?topic=A00588 )〕 * Isthmic spondylolisthesis is the most common form; also called spondylolytic spondylolisthesis, it occurs with a reported prevalence of 5–7 percent in the US population. A slip or fracture of the intravertebral joint is usually acquired between the ages of 6 and 16 years, but remains unnoticed until adulthood. Roughly 90 percent of these isthmic slips are low-grade (less than 50 percent slip) and 10 percent are high-grade (greater than 50 percent slip).〔 It is divided into three subtypes:〔http://www.orthobullets.com/spine/2038/adult-isthmic-spondylolisthesis〕 * * A: pars fatigue fracture * * B: pars elongation due to multiple healed stress fx * * C: pars acute fracture * Degenerative spondylolisthesis is a disease of the older adult that develops as a result of facet arthritis and joint remodeling. Joint arthritis, and ligamentum flavum weakness, may result in slippage of a vertebra. Degenerative forms are more likely to occur in women, persons older than fifty, and African Americans.〔 * Traumatic spondylolisthesis is rare and results from acute fractures in the neural arch, other than the pars.〔http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2843565/〕 * Pathologic spondylolisthesis has been associated with damage to the posterior elements from metastases or metabolic bone disease. These slips have been reported in cases of Paget's disease of bone, tuberculosis, giant-cell tumors, and tumor metastases.〔http://www.basicspine.com/blog/spondylolisthesis-displacement-lower-spine-injury-age/〕 * Dysplastic spondylolisthesis is a rare congenital spondylolisthesis occurring because of a malformation of the lumbosacral junction, resulting in small, incompetent facet joints. Spondylolisthesis.jpg|thumb|X-ray picture of a grade 1 isthmic spondylolisthesis at L4-5 Lumbar mri 0017 rgbc 68f.jpg|MRI of L5-S1 spondylolisthesis Spondylolistheses annotated.JPG|X-ray of a grade 4 spondylolisthesis at L5-S1 with spinal misalignment indicated 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spondylolisthesis」の詳細全文を読む スポンサード リンク
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