99mTc-labeled white blood cell scan as a guide to open biopsy in the management of hip and knee prosthesis infection: preliminary results

The aim of the present prospective study was to evaluate the usefulness of labeled leukocyte scan as a guide to open biopsy for the management of hip and knee prosthesis infection in patients without loosening of orthopedic device. Twenty-six patients with suspected hip (24) and knee (2) prosthesis infection underwent routine analysis of blood, plain radiography and 99m Tc-HMPAO labelled leukocyte scan (WBCS). On these basis, patients were subdivided in the following groups: bone infection without loosening (n°=14), septic loosening (n°=8), superficial infection (n°=2), no infection (n°=2). Patients with septic loosening underwent empirical antibiotic therapy in order to avoid two-stage re-implantation. When the medical treatment was effective patients were submitted to one-stage operation. Patients without loosening of prosthesis but positive WBCS results underwent open biopsy: bone samples and periprosthetic tissues were taken from the regions showing pathological leukocyte uptake at the scan. Samples were submitted to microbiological examination and antibiotic treatments were undertaken in cases of bacterial growth. A 24-months clinical and instrumental follow-up was carried out in all patients. WBCS showed 22 patients affected by bone infection, 2 by superficial infection and 2 not infected. Height out of the 22 patients affected by deep infection had a septic loosening. In these cases, the medical treatment was inadequate in 6 patients and effective in 2. Fourteen patients with bone infection without loosening were submitted to open biopsy: in 9 cases a complete remission of the disease was found. Two patients, without infection, underwent single-stage surgery for mechanical problems. Superficial infection was assessed and successfully treated in 2 patients. The obtained results indicate that a multidisciplinary approach to infection of orthopedic prostheses, characterized by the combined use of open biopsy, WBC, and microbiological examination, produced positive outcome in 9 out of 14 patients.