Septic arthritis of the shoulder is distinctly challenging to diagnose and treat. Guidelines for appropriate workup and management are limited and do not account for the variations in clinical presentation. The purpose of this study was to present a comprehensive and anatomically-based classification system and treatment algorithm for septic arthritis of the native shoulder joint.
A multicenter, retrospective analysis was performed at two tertiary care academic institutions for all patients treated surgically for septic arthritis of the native shoulder joint. Preoperative MRI and operative reports were used to classify patients into one of three infection subtypes: Type I (isolated to the glenohumeral joint), Type II (extraarticular extension), Type III (concomitant osteomyelitis). Based on these clinical groupings of patients, the comorbidities, surgical management and outcomes were analyzed.
Sixty-five shoulders in 64 patients met inclusion criteria for the study. Of these, 9.2% of infected shoulders were Type I, 47.7% were Type II, and 43.1% were Type III infections. Age and the time between symptom onset and diagnosis were the only significant risk factors for developing a more severe infection. Fifty-seven percent of shoulder aspirates revealed cell counts below the standard surgical cutoff of 50k cells/mL. The average patient required 2.2 surgical débridements to eradicate the infection. Infections reoccurred in 8 (12.3%) shoulders. BMI was the only risk factor for recurrence of infection. One out of the 64 patients (1.6%) died acutely secondary to sepsis and multiorgan system failure.
The authors propose a comprehensive system for the classification and management of spontaneous shoulder sepsis based on stage and anatomy. Preoperative MRI can help determine the severity of disease and aid in surgical decision-making. A systematic approach to septic arthritis of the shoulder as a unique entity from septic arthritis of other large peripheral joints may lead to more timely diagnosis and treatment and improve the overall prognosis.

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