Bone Scan: in THR

- See: Total Hip Replacement Menu:
          - General Discussion of Bone Scans:

- Normal THR:
    - normal study (minimal reative bone formation) may be expected from months to a year after placement;
    - area of lesser trochanter to midshaft of prosthesis usually becomes normal in about 6 months;
    - area around acetabulum, greater trochanter, and tip of prosthesis may show increased activity for up to 2 years, but on average shows
            normal findings at about 1 year in the majority of patients;

- Non Cemented THR:
      - evaluation of of porous coated prosthesis may require a different interpretation from cemented THR;
      - bone & fibrous tissue ingrowth into porous acetabular & intertrochanteric surfaces may cause findings unrelated to complications;
      - with loosening there is little inflammation and, therefore, the first two phases of the bone scan are normal;
      - even culture of material taken at operation, which microscopically shows presence of infected material, fails to grow microorganisms in 
              up to 10% of cases;

- Infection:
    - infection shows a more diffuse pattern of abnormality occurring along prosthesis shaft and is usually positive on the 2 early phases;
    - low grade infection may consist of minimal hyperemia & may show a mild delayed uptake on bone scan which is difficult to distinguish 
           from loosening;
    - false positive results may occur in upto 40% and false negatives in 5-10%;
    - Indium-111:
           - more specific for making definitive dx of infection but may be less sensitive

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, September 7, 2011 3:49 pm