Case Presentation: Septic arthritis (SA) of the sternoclavicular joint (SCJ) is a rare clinical entity with just over 200 cases reported in the past 45 years. We report an interesting case of SCJ septic arthritis in a patient with type one diabetes.A 47-year-old African American male with a medical history significant for poorly controlled diabetes presented to the hospital with complaints of left-sided chest pain localized to the sternal end of the clavicular bone with radiation to the neck and limitation of movement of the ipsilateral shoulder for one-week duration. He denied any history of direct trauma, intravenous drug use, recent central venous catheterizations, or infections. Chest x-ray showed non-specific findings. Additional imaging with CT and MRI of the chest revealed inflammatory changes suggestive of SCJ SA. Culture data from blood and joint aspirate were positive for Methicillin Sensitive Staphylococcus Aureus (MSSA). SCJ arthrotomy with drainage was performed and the patient was given four weeks of antibiotics.Further history from the family indicated that the patient, at times was not very sterile with his insulin injection technique. The patient also acknowledged that he is right-handed and uses his left upper arm as the preferred site for his daily injections.
Discussion: The SCJ is an unusual site of SA. It is responsible for 0.5–1.0 % of all joint infections. Patients usually present in a subacute fashion. Localized SCJ pain with ipsilateral referred neck and/or shoulder pain are the most common presenting symptoms. Exam is often limited to occasional localized swelling, tenderness, and redness. Leukocytosis, positive blood, and joint aspirate cultures are invariably present in most patients. Initial plain radiographs are usually normal. Advanced imaging with CT and MRI is superior and can reveal inflammatory changes suggestive of SA.Based on a literature review of 180 cases, Staphylococcus aureus is the most common isolated pathogen (present in 49% of patients). Various predisposing factors have been identified with the following frequencies in SCJ patients: Intravenous drug use in 36% of patients, distant site infection in 25% of patients, diabetes mellitus in 13% of patients, trauma in 12% of patients, and infected central venous line in 9% of patients.
Conclusions: The association between diabetes and this rare clinical entity is not entirely clear. Hyperglycemia-induced immunosuppression is thought to play a role. We propose that subcutaneous insulin delivery with poor skin hygiene can increase the risk of infection through a mechanism similar to that of intravenous drug users and infected central line catheters. We suspect bacterial contaminants injected into the upper extremity pass back along the course of the subclavian vein, ultimately seeding and propagating to the SCJ given their intimate anatomical association.This case highlights the importance of a comprehensive history to assess risk factors.