Effect of soft-tissue pathology on detection of pedal osteomyelitis in diabetics

Three-phase bone scans were performed on 30 diabetic patients suspected of having acute pedal osteomyelitis; 23 also had a pedal ulcer, seven had coexisting cellulitis, and 14 had diminished pedal pulses. Fifteen patients were receiving antibiotics at the time of the scan. A tissue diagnosis was available in 18 patients and 12 had no clinical evidence of infection on follow-up. Focal arterial hyperemia combined with focally increased activity on blood-pool and delayed (2-3 hr) scans were interpreted as acute osteomyelitis. Scans showing venous hyperemia were interpreted as soft-tissue pathology without acute osteomyelitis. Companion radiographs were reviewed independently. The sensitivity and specificity of the scans for osteomyelitis were 0.94 and 0.79, respectively, while radiographic sensitivity was 0.93 and specificity was 0.50. The presence of soft-tissue ulcers or cellulitis, peripheral vascular disease, or recent antibiotic therapy had no significant adverse effect on the accuracy of the three-phase scan in diagnosing osteomyelitis.