Routine Laboratory Testing Essay

Laboratory Testing Routine laboratory screening for suspected prosthetic joint infection in the setting of a painful THA includes a complete blood count with differential, C-reactive protein level (normal, 4200 cells/µL and neutrophil differential of >80% is highly suggestive for chronic infection about a THA [16]. Additionally, the onset of symptoms in relation to the primary operation can help identify the causative organism. Early (12 months) infections are commonly due to staphylococcus aureus, while delayed (3 to 12 months) infections are commonly due to propionibacterium species [17-19]. In an effort to increase diagnostic yield and decrease false-negative cultures, patients should stop antibiotics for a minimum of 2 weeks prior to
Bugbee et al. [23] devised a largely accepted radiographic classification system of osseointegration for uncemented femoral implants, and can be separated into major and minor signs. It should be noted that while these signs are useful, they are uncommon and dependent upon the prosthesis. Major signs indicating stability include a lack of radiodense lines around the porous ingrowth portion of the component and endosteal spot welds. Minor signs include a stable distal stem, calcar atrophy, and the absence of a bony pedestal at the component’s tip. We find that critical evaluation of radiographs for periprosthetic fracture, osteolysis, and implant subsidence are more important than classifying the mechanism of implant
Multiple systems [25-27] are available for describing and predicting loose cemented femoral components. Gruen et al. [25] described a classification system indicating where loosening around the femoral component may have occurred and has been shown to be reliable and reproducible (Figure 1). O’Neill and Harris define the definitive loosening of cemented femoral components as (1) implant subsidence, (2) a new prosthetic cement radiolucency, (3) a cement mantle fracture, and (4) implant fracture [28]. This widely accepted criteria is simple to use and provides a reliable method of determining whether a cemented femoral component is loose. Plain radiographs continue to play an integral role and are considered by many to be the most useful diagnostic imaging modality in the pre-operative planning phase of revision