Define Brodie’s Abscess. Describe its clinical features, investigations, management and diagnosis.

Definition

A Brodie’s abscess is a form of subacute / chronic osteomyelitis in which the infection is localised and walled off as a chronic bone abscess, usually in the metaphysis of a long bone (classically the upper tibia). It represents a balance between a relatively low-virulence organism and good host resistance, so a discrete cavity forms rather than widespread infection.

Clinical Features

The presentation is indolent: intermittent, deep pain (often worse at night) over months, with little or no fever and few systemic signs. There may be local tenderness and mild swelling. The insidious course and the radiographic appearance can mimic a bone tumour.

Investigations

• Radiographs show a well-defined, round or oval radiolucent cavity in the metaphysis surrounded by a rim of reactive sclerosis.
• MRI demonstrates the abscess and any ‘penumbra sign’. Inflammatory markers may be normal or mildly raised. The cavity contains pus or granulation tissue
• Staph.
• Aureus is the usual organism.

Management

Treatment is curettage/drainage of the abscess cavity combined with antibiotics directed against the cultured organism. Small, clearly infective lesions may respond to antibiotics with immobilisation, but most require surgical evacuation to confirm the diagnosis (and exclude a tumour) and to clear the infection.

Differential Diagnosis

Because of its indolent course and radiographic appearance, a Brodie’s abscess must be distinguished from an osteoid osteoma (also causes night pain, but shows a small nidus with dense surrounding sclerosis), eosinophilic granuloma, and low-grade bone tumours. When doubt exists, biopsy at the time of curettage both confirms infection and excludes a tumour, which is why operative evacuation is usually preferred over antibiotics alone.

Night pain relieved by aspirin mimics osteoid osteoma.

• A localised, walled-off subacute/chronic bone abscess, typically metaphyseal (upper tibia).
• Indolent deep pain, often nocturnal, with minimal systemic upset.
• X-ray: lucent cavity with a sclerotic rim; mimics a tumour or osteoid osteoma.
• Treat by curettage/drainage + culture-directed antibiotics.