Osteomyelitis of the Proximal Ulna Positive for Aeromonas sobria Presenting as Olecranon Bursitis: A Case Report

Background Osteomyelitis is a bone infection, often arising secondary to trauma or infection. It most often occurs in the long bones such as the femur and tibia, and is characterized by swelling, pain, erythema, and constitutional symptoms. Olecranon bursitis often shares many of the characteristic findings of osteomyelitis including swelling, redness, edema, and localized pain. Case Presentation We report the case of a 71-year-old female with a history of osteoporosis, hyperlipidemia, and hypothyroidism who presented with symptoms and physical exam findings consistent with olecranon bursitis, but was determined to have posterior ulnar osteomyelitis from Aeromonas sobria. Unlike the common presentations of osteomyelitis, this patient presented without fever, pain, or associated erythema of the posterior ulna. X-rays were nondiagnostic but revealed subtle changes in the proximal ulna. An MRI was obtained which was concerning for a diagnosis of osteomyelitis versus neoplasm. Operative cultures and pathology confirmed osteomyelitis, and the patient was successfully treated with debridement of the affected tissue, followed by antibiotics PO for 42 days. The patient recovered with a full range of motion after two months, with no radiographic evidence of ulno-humeral arthritis. Conclusions While olecranon bursitis is one of the most common musculoskeletal diagnoses of the elbow, osteomyelitis of the proximal ulna is exceedingly rare. While MRI is not part of the standard work-up for olecranon bursitis, in this case, it was critical for obtaining the proper diagnosis. This case illustrates the importance of accurate radiographic interpretation as well as a high index of suspicion for underlying pathology when treating routine conditions such as olecranon bursitis.