Extra‐Articular Abscess Expansion as a Specific Complication of Septic Arthritis of the Shoulder Joint: Report of Three Cases with Extension of the Infection through the Biceps Groove Producing a Large Abscess

Background Septic arthritis of shoulder is a rare clinical entity as the metaphysis is extracapsular and there is no communication between epiphyseal and metaphyseal vessels. Septic arthritis of the shoulder joint is a diagnostic and surgical emergency because joint destruction develops rapidly and can cause significant morbidity and mortality. Unusual complications of septic arthritis of the shoulder joint may include extra‐articular abscess extension to the upper arm through the biceps groove and osteomyelitis of the greater tuberosity. Case Presentation Septic arthritis of the shoulder, if left untreated, can lead to complications such as extra‐articular abscess extension and osteomyelitis. Three patients with septic arthritis of the shoulder joint with no clear history of trauma were reported in this study. The initial presentation was pseudoparalysis with upper arm swelling. MRI diagnosed septic arthritis of shoulder joint together with an upper arm abscess. Arthroscopic debridement with through irrigation and open drainage of the extra‐articular abscess extension to the upper arm improved both the shoulder pain and abscess completely. However, if shoulder pain or abnormalities in laboratory findings continue after initial treatment, uncontrolled septic arthritis or secondary osteomyelitis are possibilities that should be concerned. MRI is a useful tool for detecting those atypical complications. Conclusions Rarely, septic arthritis of the shoulder joint can extend to the upper arm through the biceps tendon groove and cause an abscess. Also, acute osteomyelitis of the tuberosity should be considered in patients with long‐standing refractory septic arthritis of the shoulder joint who have continued pain and uncontrolled laboratory findings after initial treatment.