Bone scan, gallium scan, and hip aspiration in the diagnosis of infected total hip arthroplasty.

The difficulty in differentiating aseptic loosening from infection in painful total hip arthroplasty is well recognized. This prompted a review of the efficacy of the preoperative investigations used at the authors' institution. One hundred forty-four patients who underwent revision hip arthroplasty were reviewed. Seventy-two had sequential bone-gallium scan, and/or hip aspiration, and intraoperative Gram stain. These were compared to intraoperative culture as the gold standard. Twenty infected hips were detected on culture. For prediction of infection, the bone-gallium scan had a sensitivity of 38% and a specificity of 100%. Hip aspiration had a sensitivity of 57% and a specificity of 97%. The investigations combined gave a sensitivity of 64% and a specificity of 95%. Intraoperative Gram stain compared with subsequent culture yielded a sensitivity of 23% and a specificity of 100%. Uncemented hips were infected more frequently (47%) than cemented hips (9%), significant at P < .0001. It was concluded that bone-gallium imaging is not an effective method for investigating painful hip prostheses for sepsis and offers no additional advantage over hip aspiration. Intraoperative Gram stain also missed a large number of infections. Other modalities, such as indium-labeled-leukocyte imaging and capsular histologic examination, may be more efficacious. A significant difference in the number of infections found in cemented versus uncemented hips was shown, hence greater vigilance for infection is required when patients present with painful uncemented hip arthroplasties.