Brodie’s abscess presenting in a young soccer player following ankle injury

Abstract

Brodie’s abscess is a localized form of subacute osteomyelitis that typically occurs in the growing ends of long bones in the lower limbs of young adults. It is rare and potentially serious if the diagnosis is delayed. A high index of suspicion is required to diagnose the condition and persistent pain following an injury should alert the treating doctor to the possibility of this condition and not to simply attribute the pain to the original injury. This letter aims to highlight this rare occurrence with the case of an 11-year-old soccer player who suffered a noncontact eversion injury to his right ankle. At initial presentation he was found to have an avulsion fracture of the right medial malleolus on plain radiographic evaluation and was managed with below knee cast immobilisation for 4 weeks. Ten weeks following the injury he began to feel increasing discomfort in the anterior aspect of his right distal shin. Subsequent radiographs of his right ankle showed a lesion in the lower tibial metaphysis, which was of mixed sclerotic and lytic nature that did not appear to breach the cortex with no associated periosteal reaction. Subsequent magnetic resonance imaging (MRI) of the right ankle demonstrated a well-defined lesion crossing the growth plate in keeping with a Brodie’s abscess (Fig. 1). Contemporaneous haematological investigations revealed a raised C-reactive protein (CRP) at 19.5 mg/l (normal \ 5 mg/l) with a normal white cell count (WCC) and erythrocyte sedimentation rate (ESR). Aerobic and anaerobic blood cultures failed to grow any organisms. Despite antibiotic therapy, his blood tests showed a worsening picture of inflammation and he developed erythema over the lateral aspect of his right ankle. He was subsequently taken to theatre and 8 ml of pus was aspirated from his ankle joint. Culture of the pus aspirated from the ankle grew no organisms. He underwent further operative washout of his right ankle 4 days later and completed a 6-week course of antibiotics. Following this, he went on to make a good recovery and at 1-year follow up he is asymptomatic and back playing soccer. A Brodie’s abscess may be mistaken for a variety of neoplasms including Ewing’s sarcoma and osteoid osteoma. In as many as 50% of cases, subacute osteomyelitis is confused with tumour and biopsy is sometimes required for definitive diagnosis [1]. The incidence of osteomyelitis in children is 2.9 new cases per 100,000 population per year [2]. Pain is the most consistent symptom and constitutional symptoms are usually mild. C-reactive protein (CRP) has been found to be superior than ESR or WCC in monitoring the effectiveness of therapy and predicting recovery from acute haematogenous osteomyelitis [3]. Blood cultures are seldom positive and abscess culture may be negative in as many as 50% of cases [4]. This may in part be because the patient has already received antibiotic treatment. If cultures are positive then typically Staphylococcus aureus is isolated [4], although a number of other causative organisms such as streptococci, pneumococci, and Gram-negative bacteria have also been isolated [2]. Magnetic Resonance (MR) Imaging is a useful tool for evaluating patients with osteomyelitis and has been shown to be superior to bone scanning. MR provides better soft tissue resolution and is more useful in differentiating S. P. Edmundson (&) K. M. Hirpara P. O’Grady Department of Trauma and Orthopaedics, Mayo General Hospital, Castlebar, County Mayo, Ireland e-mail: stevenedmundson@yahoo.co.uk