PRIMARY SUBACUTE PYOGENIC OSTEOMYELITIS

Abstract

1. A primary subacute type of staphylococcal osteomyelitis has been described. It is the commonest form of osteomyelitis seen in East Africa, and the incidence appears to be increasing in Great Britain. 2. A review of the literature indicates that this is not a new disease but that in the past there has been some confusion in terminology. 3. The causative organism is a coagulase positive staphylococcus, but in a few instances a coagulase negative one has been isolated. The staphylococcus is thought to be of reduced virulence and in East Africa it is likely that the population has acquired an increased resistance to the staphylococcus. 4. Two radiologically distinct groups are recognised, depending on whether a bone abscess is present or not. In the first group there are two types of localised abscesses: the familiar Brodie's lesion and the less well recognised large bone abscess that occurs in the metaphysis of a long bone. While the pathology of the two types is similar, the radiological features are quite distinct. The lesions in the second group are characterised by extensive diaphysial changes, with or without metaphysial involvement, and an obvious abscess cannot usually be demonstrated. 5. The main clinical features are the long history, often weeks or months, before diagnosis; insignificant or absent general reaction to the infection and minimum physical signs. 6. Vertebral body osteomyelitis in adults is included because it generally presents as a subacute infection; the difficulties in distinguishing it from a tuberculous infection are outlined. 7. The most useful diagnostic aids are the staphylococcal antibody titres (especially in vertebral infections) and the erythrocyte sedimentation rate. A limited surgical exposure is usually required if the causative organism is to be isolated and empirical antibiotic therapy is to be avoided. The total and differential white blood count are so often normal in these patients that they are considered to be of no diagnostic value. 8. Curettage and local antibiotics together will cure the localised bone abscess. Other lesions may be effectively treated by systemic antibiotics alone, but in the later stages removal of sequestra and infected granulation tissue may be necessary. In this instance it is essential to make a planned incision and to cut a window in the bone large enough to expose the whole of the lesion; primary suture of the wound is advocated.