Abstract
Infection after total joint arthroplasty can present a diagnostic challenge. No preoperative tests are consistently 100% sensitive and specific, so the diagnosis of infection depends on the surgeon’s judgment with respect to the clinical presentation and examination and interpretation of the results of investigations. The consequences of misdiagnosis are severe. Reimplantation of a prosthesis into an infected host bed is likely to result in persistent infection.
Preoperative investigations include haematological screening tests (white blood cell count, ESR, and C-reactive protein), joint aspiration and arthrography, radiography, and radionuclide imaging studies. Intraoperative investigations include analysis of synovial fluid, gram-staining of tissue that appears inflamed, histological evaluation of frozen sections of inflamed tissue, and culture of periprosthetic tissue. The exclusion of infection as a cause of failure is imperative to determine the management of patients who need revision total joint replacement. The key to making the correct diagnosis is using not a single investigation but rather a correct combination of investigations.
From 2001 to 2004 we studied 46 patients referred from various centres with prosthesis loosening. The patients had technetium and gallium scintigraphy. In 32 patients, scintigraphic studies suggested septic loosening. Of these, 21 patients also had aspirations, three intraoperative cultures and 11 both aspirations and intraoperative cultures. The remaining 11 patients had aseptic loosening and were used as a control group. In only 10 patients was sepsis proved by aspiration or culture.
Our results, which show that scintigraphy has a dismal positive predictive value as a screening test and a good negative predictive value, concur with the current literature.
Secretary: Dr H.J.S. Colyn, Editor: Professor M.B.E. Sweet. Correspondence should be addressed to SAOA, Box 47363, Parklands, Johannesburg, 2121, South Africa.
