Case Presentation: Our vignette is of a 14-year-old female who presented to the emergency room for complaints of right elbow pain and swelling. Patient underwent open reduction internal fixation (ORIF) for right elbow fracture when she was 2-years old. The hardware was removed successfully after the fracture healed. Since then, the patient had 3 fractures and intermittent pain and swelling of the right elbow every few months that was managed with ibuprofen. This time, the patient’s symptoms were unresponsive to ibuprofen. She also reported tingling sensation in her fingers. She denied fever, chills, sweats, weight loss, or trauma. Physical exam was remarkable for tenderness to palpation of elbow with increased warmth. Laboratory evaluation showed neutrophilic leukocytosis (WBC count: 15,300/uL with absolute neutrophil count of 13,720; normal(N): 4.5-13 x 103/uL), high CRP (14.80 mg/dL, N: < 0.30 mg/dL) and high sedimentation rate (40 mm/hr, N: 0-20 mm/hr). X-ray of the right elbow showed findings concerning for occult fracture. MRI was remarkable for osteomyelitis of right distal humerus with capitellar Brodie’s abscess measuring 7 mm, communicating with the joint space via a ventral sinus tract. Elbow joint capsular distention with effusion and synovial hypertrophy, consistent with septic arthritis, was also noted. Patient was taken to the operating room for incision, drainage and debridement of right septic elbow immediately. Copious purulent drainage from the joint and a bone abscess in the anterior distal humerus were noted. Wound cultures were sent, and the patient was started on clindamycin post-procedure. Wound cultures were positive for Serratia marcescens, sensitive to ciprofloxacin. Patient improved after switching the antibiotic to ciprofloxacin and was discharged home to complete a 6-month course. Patient was seen 6-months after discharge, and she reported no recurrence of symptoms. Post-treatment imaging was unremarkable except for chronic remodeling from previous fractures.

Discussion: Brodie’s abscess is an intraosseous abscess formed due to subacute/chronic osteomyelitis, that has a characteristic radiographic finding of a ‘penumbra sign’- 4 concentric layers of central necrotic core, granulation, fibrosis and edema. Clinical findings include pain and swelling of affected extremity with or without fever. Long bones are common sites of abscess formation. Staphylococcus is the most common organism associated with it. Diagnosis is often delayed due to absence of signs of systemic inflammation clinically or on laboratory evaluation. Our case is unique because Serratia marcescens, a rare bacterium, was causative of the abscess in this immunocompetent patient. We strongly suspect that the organism was introduced by the hardware used in the original fixation of elbow fracture. Even after removal of the hardware, the organism persisted to cause subacute inflammation and/or infection leading to a weak lamellar matrix resulting in multiple pathological fractures during her childhood at the same site. This continued into the patient’s early adolescent years causing recurring elbow pain and swelling before presenting as septic arthritis.

Conclusions: Brodie’s abscess should be suspected and promptly evaluated in recurrent non-traumatic bone pain, swelling and fractures in pediatric patients to prevent associated complications such as loss of growth plate by providing treatment in a timely manner. This also prevents multiple hospitalizations and costs associated with these admissions.

IMAGE 1: MRI of the right elbow showing a focal hyperintense T2 signal lytic process at the level of the capitellum, measuring 7 mm consistent with Brodie’s abscess.