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Radiolucent Lines: Loose THR

- Discussion:
    - progressive enlargment radiolucent line size on serial radiographs;
    - radiolucencies between cement & femoral cortex in immediate postop period may be produced by cancellous bone that was not removed;
          - however, it is impossible to tell whether cancellous bone was not curreted or the canal was not filled with cement;
          - absorption of bone from the medial cortex of the femoral neck up to several milimeters is not considered abnormal;
          - radiolucency between cement & medial cortex of neck may be produced by dense cancellous bone that the surgeon elected not to 
                 remove, believing that it was dense enough to support cement;
    - radiolucent line w/ surrounding thin line of denseness in bone may develop about all or part of the cement mass;
    - any increase in the width of the radiolucent line to more than 2 mm, esp if it develops more than 6 months after surgery;
    - development of area of radiolucency between stem & surrounding cement is a definite sign of loosening;
    - radiolucency between the superolateral 1/3 of the stem and the adjacent cement mass, indicates loosening of the stem in the cement and
          possible early deformation of the stem;
    - circumferential radiolucency:
          - radiolucency > 2 mm surrounding acetabular cup or circumferential lucency around the femoral component represent probable radiologic loosening;
          - by definition lossening is present if radiolucent zone > 2 mm wide is seen, especially if noted abaout the entire cement mass

- Possible Radiologic Loosening:
     - physiologically, a membrane upto 2 mm in width is present at cement bone interface that may  or may not be seen in the x-ray;
     - incomplete radiolucent lines around either femoral or acetabular component that encompass upto 50% of bone-cement interface;
     - physiologically, a membrane upto 2 mm in width is present at the cement bone interface that may or may not be seen on x-ray;
     - therefore, loosening is present if a radiolucent zone more than 2 mm wide is seen, especially if note about the entire cement mass, and
           if it increases progressively in width