Periarticular bone sites associated with traumatic injury: false-positive findings with In-111-labeled white blood cell and Tc-99m MDP scintigraphy.

The authors evaluate the reliability of combined indium-111-labeled white blood cell (WBC) and technetium-99m methylene diphosphonate (MDP) bone scan interpretations at sites of suspected periarticular osteomyelitis with radiographic evidence of adjacent traumatic arthropathy. A review of all orthopedic patients who underwent In-111 WBC-Tc-99m MDP scintigraphy over a 7-year period revealed a subset of 32 such cases that also included results of bone-biopsy cultures. Twenty-eight patients had a history of traumatic intraarticular injury, and four had periarticular fracture malunion or nonunion. Compared with intraoperative culture results, blinded In-111 WBC-Tc-99m MDP scan interpretations included four true-positive, 17 true-negative, and 10 false-positive results, and one false-negative result. The predictive values for positive and negative scans were 28% and 94%, respectively. A high prevalence of false-positive In-111 WBC-Tc-99m MDP scans may occur at periarticular sites of patients with associated traumatic arthropathy. This reduces the specificity of this technique for osteomyelitis, making culture confirmation of positive scans necessary. A negative scan is highly predictive of negative culture results at these sites.