Painful knee in neonatal -Case1
A young primigravida mother has become concerned about her newborn child. She is accompanied in the clinic by her aunt who recognized that something was not quite right but was not sure what to advise. The baby has general symptoms of fever, fatigue, irritability and malaise. There is no history of trauma.
Close inspection of the left leg reveals some localized oedema and erythema. On palpation the baby appears to have pain overlying the proximal tibia. Passive manipulation to the baby shows a full range of movement of the leg without any obvious indications of pain.
Initial investigations show a markedly elevated C-reactive protein (CRP). Imaging studies a full range of movement of the leg without any obvious indications of pain.
• What is the diagnosis?
• What are the radiological signs?
• What blood tests would be most useful?
The diagnosis is acute haematogenous osteomyelitis. Septic arthritis is less likely in view of the excellent range of movement. There are two principal types of acute osteomyelitis:
• haematogenous osteomyelitis
• direct or contiguous inoculation osteomyelitis.
Acute haematogenous osteomyelitis is characterized by an acute infection of the bone caused by the seeding of the bacteria within the bone from a foreign source.
This condition occurs primarily in children. the foremost common site is growing rapidly and highly vascular metaphysis of growing bones. During trauma or surgery direct or contiguous inoculation osteomyelitis is caused by direct contact of the tissue and bacteria. Clinical manifestations are more localized and have a tendency to involve multiple organisms.
Predisposing comorbidities include DM , red blood cell disease, acquired immune deficiency syndrome (AIDS), intravenous substance abuse, alcoholism, chronic steroid use, immunosuppression, and chronic joint disease. Other possibilities are the presence of a prosthetic orthopaedic device, recent orthopaedic surgery or an compound fracture.
In general, osteomyelitis features a bimodal age distribution. Acute haematogenous osteomyelitis is primarily a disease in children. Comparing to children direct trauma and contiguous focus osteomyelitis are more common among adults and adolescents. Spinal osteomyelitis is more common in individuals older than 45 years.
The bacterial pathogen varies on the idea of the patient’s age and therefore the mechanism of infection:
• In neonates (<4 months) – Staphylococcus aureus, Enterobacter spp, and group A and B Streptococcus spp
• In children (4 months to 4 years) – S. aureus, group A Streptococcus spp, Haemophilus influenzae and Enterobacter spp
• In children and adolescents (4 years to adult) – S. aureus (80 per cent), group A Streptococcus spp, H. influenzae and Enterobacter spp
• In adults – S. aureus and occasionally Enterobacter or Streptococcus spp.
Responsible pathogens may be isolated in only 35–40 per cent of infections.
With direct osteomyelitis the organisms include S. aureus, Enterobacter spp and Pseudomonas spp. In the presence of puncture wounds there may be S. aureus and Pseudomonas spp; and in the presence of sickle cell disease, S. aureus and Salmonella spp.
Appropriate antibiotics are selected using direct culture results. Empirical therapy is often initiated on the basis of the patient’s age and the clinical presentation. Further surgical management may involve removal of the nidus of infection and implantation of antibiotic beads until resolution of the infection.
Plain radiographs may show evidence of soft-tissue swelling after 3–5 days. Bony changes are usually present at 14–21 days. The earliest bony changes are periosteal elevation followed by cortical or medullary lucencies. At 28 days, 90 per cent of patients demonstrate some abnormality. Magnetic resonance imaging (MRI) is effective in the early detection of osteomyelitis with a sensitivity ranging from 90 to 100 per cent. Radionuclide bone scanning using a 3-phase bone scan with technetium-99m may show up increased tracer uptake in the affected region.
Additional information can be obtained from scanning with leucocytes labelled with gallium-67 and/or indium-111. Computed tomography (CT) scanning can demonstrate calcification, ossification, and intracortical abnormalities. CT is particularly helpful in the evaluation of spinal vertebral lesions. Ultrasonography is useful in children with acute osteomyelitis. This modality can detect abnormalities as early as 1–2 days after onset of symptoms. The abnormalities include soft-tissue abscess or fluid collection and periosteal elevation.
The white cell count may be elevated, but it is frequently normal. The C-reactive protein level is usually elevated, but this is non-specific. The erythrocyte sedimentation rate (ESR) is elevated in 90 per cent, but this finding is clinically non-specific. Blood culture results are positive in only 50 per cent of patients with haematogenous osteomyelitis. Culture or aspiration findings in samples of the infected site are normal in 25 per cent of cases.
• Osteomyelitis can be a result of haematogenous or direct spread.
• The earliest radiographic change is periosteal elevation.
• MRI is effective in the early detection of osteomyelitis.
• The bacterial pathogen varies on the basis of the patient’s age and mechanism of infection.