Infectious Costochondritis With Sternal Osteomyelitis

Costochondritis is primarily caused by physical exertion, repetitive movements (such as lifting heavy objects), and severe coughing. Although it is an inflammatory condition, it is not an infection and is often treated with non-steroidal anti-inflammatory drugs (NSAIDs). In contrast, infectious costochondritis usually develops when an infection spreads directly from a postoperative wound or adjacent foci. We present a case of infectious costochondritis with sternal osteomyelitis caused by <i>Pseudomonas aeruginosa</i>, where the infection did not spread from adjacent tissues. A 59-year-old man was referred to our hospital with anterior chest pain and swelling persisting for three months. He had been diagnosed with diabetes mellitus three years prior. Three weeks before his visit, a purulent exudate had fistulized into the skin. Two weeks prior, he had sought care from a nearby doctor, who diagnosed a subcutaneous abscess and performed an incision and drainage. Cultures identified <i>P. aeruginosa</i>. However, the condition did not improve, and chest computed tomography (CT) was performed, showing edema around the seventh costal cartilage, the inferior end of the sternum, and surrounding subcutaneous tissue. Distraction of the seventh costal cartilage was also noted. Magnetic resonance imaging (MRI) with fat-suppressed T2-weighted images showed high intensity in the same area. Blood cultures were negative. Based on these findings, we diagnosed costochondritis and sternal osteomyelitis. Treatment began with oral cefalexin (CEX) for seven days, followed by oral cefcapene pivoxil hydrochloride hydrate (CFPN-PI) for 14 days. During hospitalization, meropenem hydrate (MEPM) was administered. After seven days of MEPM, the seventh costal cartilage and part of the sternum were debrided under general anesthesia. Indicators of the extent of debridement included preoperative MRI, bone cortex hardness under intraoperative palpation, and bone bleeding. MEPM was administered for 14 days, including preoperative treatment, followed by cefepime dihydrochloride hydrate (CFPM) for 14 days and levofloxacin hydrate (LVFX) for seven days. After 11 months of follow-up, there was no recurrence of costochondritis or osteomyelitis. Infectious costochondritis with sternal osteomyelitis caused by <i>P. aeruginosa</i> was successfully treated with debridement. Properly determining the extent of debridement perioperatively is crucial for effective treatment.