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- Types of Spondylolisthesis:
     - Congenital
     - Isthmic
     - Degenerative
     - Spondylolysis of the Fourth Lumbar Vertebra
     - Spondylolisthesis w/ Scoliosis

- Discussion:
     - spondylolysis involves defect passing between superior articular process & remainder of the lamina, most often involving L5;
     - when condition is bilateral, superior articular processes are attached to the body by pedicles, but most of the lamina, spinous
           process, and inferior articular processes are detached;
           - as consequence of defect, body of involved vertebra may displace anteriorly (spondylolisthesis).
     - scoliosis is common w/ spondylolysis but herniation of the nucleus pulposus rarely accompanies spondylolisthesis in children;
     - diff dx:

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- Exam:

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- Radiographs:
     - x-rays are taken in the stading position to accentuate slippage;
     - slip angle: most useful measurement in predicting the likelihood of progression;
     - Grade I:   (see: occult spondylysis)
     - Grade II:
     - Grade III and IV:
     - Slip Angle;
     - Bone Scans

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- Treatment:
    - Grade I:
    - Grade II:
          - surgery is reserved for patients w/ intractable pain who have failed non-operative treatment, or w/ progressive deformity;
          - treatment involves L5-S1 posterolateral fusion in situ;
    - Grade III and IV:
          - high risk of L5 nerve root impingement;
          - treatment involves arthrodesis from L4 to S1;
    - Reduction:
    - Decompression:
          - as noted by Carragee (1997), the addition of decompression to the posterolateral arthrodesis may actually increase the rate of 
                pseudoarthrosis and the rate of clinical failure;
          - reference:
                - Single-level posterolateral arthrodesis, with or without posterior decompression, for the treatment of isthmic spondylolisthesis in adults. A prospective, randomized study.

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- References: