TC-99M-POLYCLONAL IGG AND TC-99M NANOCOLLOID SCANS IN ORTHOPEDICS - ACOMPARISON WITH CONVENTIONAL BONE-SCAN

The bone scan is sensitive in detection of active bone/joint lesions. A normal bone scan virtually excludes the presence of an inflammatory process with high precision, but the poor specificity of bone scans is well known. In recent years, various new agents including Tc-99m-hexa methylpropylene amine oxime (HMPAO)-labelled white blood cells, nanoco lloid, polyclonal IgG, anti-granulocyte antibody, In-111-labelled IgG, leucocytes, chemotactic peptides etc. have been widely evaluated in i nflammatory imaging, especially in the orthopaedic context. This study was undertaken to compare the usefulness of Tc-99m-nanocolloid and Tc -99m-polyclonal IgG in the detection of focal bone/joint inflammation. Twenty-seven patients with a common presentation of bone/joint pain r esulting from various pathologies were included in the study. A total of 47 lesions were imaged. The overall sensitivity and specificity of both nanocolloid scan and IgG scan were identical with 95% sensitivity and 100% specificity, in detecting inflammatory foci. However, specif icity dropped to 18% with nanocolloid scans and 16% with IgG scans whe n an attempt was made to distinguish noninfective from infective infla mmatory processes; thus neither type of scan permits differentiation b etween septic and nonseptic inflammatory processes with sufficient acc uracy. As both nanocolloid and IgG scans are equally sensitive and spe cific in detecting inflammation, the choice of type of scan will depen d on cost, imaging time and availability of the radiopharmaceutical.