Spondylolisthesis

Forward movement of one building block of the spine (vertebra) in relation to an adjacent vertebra.

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Forward movement of the body of one of the lower lumbar vertebrae on the vertebra below it, or upon the sacrum. SYN: spondyloptosis. [spondylo- + G. olisthesis, a slipping and falling]

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spon·dy·lo·lis·the·sis .spän-də-lō-lis-'thē-səs n forward displacement of a lumbar vertebra on the one below it and esp. of the fifth lumbar vertebra on the sacrum producing pain by compression of nerve roots

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n.

a forward shift of one vertebra upon another, due to a defect in the bone or in the joints that normally bind them together. This may be congenital or develop after injury. The vertebral displacement is most likely to occur in the lumbar (lower back) or cervical (neck) regions of the backbone. The majority of cases in which pain is present are treated with rest and a surgical belt or corset; in a small minority, showing severe disability or pressure on nerve roots, surgical fusion may be required.

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spon·dy·lo·lis·the·sis (spon″də-lo-lis-theґsis) [spondyl- + olisthe + -sis] forward displacement (olisthy) of one vertebra over another, usually of the fifth lumbar over the body of the sacrum, or of the fourth lumbar over the fifth, usually due to a developmental defect in the pars interarticularis. spondylolisthetic adj

Spondylolisthesis due to spondylolysis; discontinuity of the posterior elements of L5 allowed forward slippage of L5 on S1.