Osteomyelitis

Acute osteomyelitis
Acute Osteomyelitis presents with an acute pyrexia illness. The child is toxic and ill and complains of bone pain. In South Africa osteitis is common, and must be suspected in any child who presents with a painful limb together with a pyrexia illness. In a late case the limb may be swollen, with pitting oedema resembling cellulitis. Children seldom develop cellulitis without an underlying cause - consider osteomyelitis in all children with "Cellulitis". Before antibiotics the mortality from this illness we 20-30%, but today fatalities are rare. There is, however much morbidity, especially if the diagnosis is delayed and chronic osteomyelitis develops.
Pathogenesis
The primary septic focus is often a septic skin lesion such as scabies, a septic tooth or other lesion. The child is often undernourished and the disease is often associated with poverty. There may be a history of minor trauma, the organisms seed to the metaphysis and form a small abscess, perhaps in the pre-existing haematoma. The pus builds up in the metaphysis and later escapes under the periosteum.

By this time there is a general septicemia and the child is toxically ill.In some areas such as the hip and knee the metaphysis is partially intra capsular and escape of this pus can cause a septic arthritis to complicate the original osteomyelitis. The growth plate acts as a barrier and the pus cannot cross it directly into the joint.
Acute Osteomyelitis is a disease of children. In adults only the vertebrae can be infected. In children all long bones can be affected especially the proximal femur and about the knee. The pelvis and vertebrae are also often affected in children.
The septicemia can seed organisms to other bones and other systemic complications such as meningitis, bronchopneumonia and pericarditis are common. The child may present primarily to the paediatric casualty with these complaints and the bone infection can be overlooked.

The causative organism in 95% of cases is Staphylococcus aureus. Haemophyllis influenza is common under 2 years of age. In the immune suppressed, virtually any organism can be the cause.

The first X Ray signs of osteomyelitis begin at about day 10,when a periosteal reactionwill be seen

Early OsteomyelitisThe right hip joint space is widened due to septic arthritis.In the hip, pus can cross from the metaphysis into the jointspace, as the synovial space partially crosses over the metaphysis.The metaphyseal area is osteopaenic and three drill holes are notedfrom a surgical drainage.

Clinical
By the time most children present to casualty they are ill and dehydrated. There is bone pain and tenderness. Percussion over a bony prominence near the infected area produces acute pain.
Remember to examine the child thoroughly for other areas of osteomyelitis as well s to move the joints for sighs of septic arthritis. If the child has been on oral antibiotics the above signs may be masked and the diagnosis is thus more difficult. Check the neck for signs of meningism. Listen to the lungs and heart for signs of pneumonia or a pericardial friction rub.

Special Investigations
The white cell count and ESR are raised. Take blood for a blood culture - positive in 80%. A Technetium scan will be positive, but is time consuming and is not usually necessary as the diagnosis can be made without it. There is more urgency to get the child to theater and drain the bone.
X Rays are normal, except for possible soft tissue swelling. Check for effusions in adjacent joints - this may denote septic arthritis or a sympathetic effusion secondary to the inflammation caused by the osteitis. After about 10 days signs such as a periosteal reaction will appear. If treatment does not abort progress of the infection, signs of chronic osteitis such as invulucrum and sequestrum will become visible on x ray.

The same child as above at about 1 month after presentation. A periosteal reaction can be seen and the femur is osteopaenic. The osteomyelitis has not resolved despite drainage and antibiotics and is becoming chronic. At this stage there is a real danger of femur fracture



X Ray of right femur of the above child 1 year later. Chronic osteomyelitis has developed and the femoral shaft has become sclerotic with invulucrum (new bone) formation. A sequestrum can be seen in the upper third of the shaft.




Lateral x ray.
Note the sequestrum appearing as a 'bone - within - a - bone'

Chronic osteomyelitis of right humerus

Reference:Acute Osteomyelitis
Department of Orthopaedic Surgery - Stellenbosch University