What is the most common level an isthmic spondylolisthesis occurs at?

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Multiple Choice

What is the most common level an isthmic spondylolisthesis occurs at?

Isthmic spondylolisthesis happens when a defect in the pars interarticularis allows one vertebra to slip forward. This most often occurs at the lumbosacral junction, specifically the fifth lumbar vertebra slipping over the first sacral segment, because that area bears the greatest shear forces and lever arm from the transition between the mobile lumbar spine and the fixed sacrum. Repetitive extension and stress during adolescence predispose the pars to fracture there, making L5–S1 the site you see most often. Other lumbar levels can slip, but they’re far less common due to lower shear forces and different facet dynamics.

Isthmic spondylolisthesis happens when a defect in the pars interarticularis allows one vertebra to slip forward. This most often occurs at the lumbosacral junction, specifically the fifth lumbar vertebra slipping over the first sacral segment, because that area bears the greatest shear forces and lever arm from the transition between the mobile lumbar spine and the fixed sacrum. Repetitive extension and stress during adolescence predispose the pars to fracture there, making L5–S1 the site you see most often. Other lumbar levels can slip, but they’re far less common due to lower shear forces and different facet dynamics.

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