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Spondylolisthesis: Radiographic Findings


- Discussion:
    - spondylolysis refers to radiolucent defect of pars interarticularis;
    - if defect is large, it is seen on nearly all x-rays of lumbar spine;
    - if it is unilateral, as it is in 20 to 25 per cent of patients, or if it is not accompanied by spondylolisthesis, it is 
           subtle finding;
    - if child is being followed for progression of spondylolisthesis, radiographic technique must be identical at each visit;
    - lateral radiograph, made w/ patient standing, is preferred;
    - in adults, degree of slip is not altered by the position of body, and radiographs that are made w/ patient recumbent are satisfactory;

- Olbique Views:
    - dx will be missed in 20 % of young symptomatic patients if oblique radiographs are not made;
    - Scotty-dog sign of Lachapele, w/ defect appearing as a collar around the dog's neck is seen;
    - in pt who has acute injury, gap is narrow & has irregular edges, whereas in pt who has long-standing lesion, edges are smooth & rounded,
            suggesting a pseudarthrosis;
    - width of gap depends on amount of resorption of bone after frx & on degree of spondylolisthesis;
    - example of normal view:  

- Tangential Slipping:
    - fifth lumbar vertebra slides forward on 1st sacral vertebra;
    - top of sacrum is divided into four equal sections;
         - slip in first quarter of the sacrum is grade I
         - slip in last quarter is grade IV;
         - grade V represents complete spondyloptosis;
    - slip measurement:
         - overlap of posterior part of cortex of L5 to posterior part of cortex of S1 is divided by maximum AP diameter of first sacral vertebra;
- Bone Scan: may be indicated w/ negative radiographic findings;

- Angular Slippage:

Radiographic evaluation of instability in spondylolisthesis.