- Discussion: 
    - evaluation of painful THR: 
    - when previously pain free hip becomes painful, suspect loosening; 
    - where as acetabular loosening tends to cause groin pain, femoral loosening tends to cause thigh pain; 
    - increased limp and shortening are signs of subsidence; 
    - patient may need to use his hands to lift leg onto exam table; 
    - inability to perform straigt leg raises; 
    - patient may then complain that his leg has become increasingly externally rotated as the component sinks into retroversion; 
    - in a cemented hip, thigh pain of implant origin indicates loosening, however, this is not necessarily the case with uncemented stems; 
    - Types of Femoral Component Loosening: 
         - cemented femoral component: loosening: 
         - bending cantilever 
         - calcar pivot: (distal toggle) 
         - medial midstem pivot 
         - pistoning: 
- Radiologic Findings: 
    - radiology of press fit stems 
    - radiology of cemented stems 
    - radiology of the acetabular component 
- Differential Injections: (see painful THR)
    - intra-articular injection of marcaine can be used in the diagnosis of component loosening; 
    - in the study by Crawford RW, et al (1997), 15 patients with a painful THR received a marcaine injection; 
          - 14 patients received relief with the injection and 13 of them were found to have loose components (either femoral and/or acetabular); 
                 - it did not seem to matter whether components were cemented or press fit; 
          - hip was aspirated and any fluid obtained was sent for culture, and if fluid was not obtained then inject 5 ml of Hartman's syndrome and re-aspirate; 
          - after aspiration, 10 cc of marcaine is injected 
Intra-articular local anesthesia for pain after hip arthroplasty.
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