The sternoclavicular joint: can imaging differentiate infection from degenerative change?

OBJECTIVE: The purpose of this study was to determine if there are imaging and clinical findings that can differentiate a septic sternoclavicular joint from a degenerative one.
MATERIALS AND METHODS: Search of radiology reports from 2000-2007 revealed 460 subjects with imaging of the sternoclavicular joint, of whom 38 had undergone aspiration or biopsy. The final study group consisted of nine subjects with pathologic proof of sternoclavicular joint infection and ten subjects with pathologic and clinical findings excluding infection consistent with degenerative change. Available ultrasound, computed tomography (CT), and magnetic resonance (MR) images were retrospectively reviewed, and echogenicity, capsular distention, erosions, cysts, hyperemia or enhancement, and intensity of bone marrow signal were recorded. Clinical data were also reviewed.
FINDINGS: The findings significantly associated with sternoclavicular joint infection included degree and extent of capsular distention. With infection, average joint distention was 14 mm (range 10-20 mm) and extended over the sternum and clavicle in 60% compared to 5 mm (range 3-8 mm) with degeneration only extending over the clavicle. Other findings significantly associated with infection included bone marrow fluid signal on magnetic resonance imaging (MRI), elevated Westergren red blood cell sedimentation rate, and fever. The two findings significantly associated with degeneration were subchondral cysts on CT and female gender. Other imaging and clinical variables showed no significant differences between infection and degenerative change.
CONCLUSION: The clinical and imaging findings significantly associated with sternoclavicular joint infection included joint capsule distention of 10 mm or greater, extension over both the clavicle and sternum, adjacent fluid signal bone marrow replacement, elevated Westergren red blood cell sedimentation rate, and fever.