First site to involve in hematogenous osteomyelitis
|D||Entry of the nutrient artery|
a. Acute hematogenous osteomyelitis is the most common type of bone infection and usually is seen in children. The incidence of acute hematogenous osteomyelitis has decreased dramatically over the last several decades.
b. In children, the infection generally involves the metaphyses of rapidly growing long bones. Bacterial seeding leads to an inflammatory reaction, which can cause local ischemic necrosis of bone and subsequent abscess formation.
c. In children younger than 2 years, some blood vessels cross the physis and may allow the spread of infection into the epiphysis. For this reason, infants are susceptible to limb shortening or angular deformity if the physis or epiphysis is damaged from the infection.
d. Otherwise, the physis acts as a barrier that prevents the direct spread of a metaphyseal abscess into the epiphysis.
e. The metaphysis has relatively fewer phagocytic cells than the physis or diaphysis, allowing infection to occur more easily in this area.
f. Staphylococcus aureus is the most common infecting organism found in older children and adults with osteomyelitis. Gram-negative bacteria have been found to cause an increasing number of vertebral body infections in adults. Pseudomonas is the most common infecting organism found in intravenous drug abusers with osteomyelitis.
g. In infants with acute hematogenous osteomyelitis, S. aureus is still a frequent isolate, but group B streptococcus and gram-negative coliforms also are commonly found. S. aureus or gram-negative organisms are the usual cause of orthopaedic infections found in premature infants undergoing treatment in the neonatal intensive care unit; more than 40% have multifocal involvement.
h. Group B streptococcus is the most likely infecting organism found in otherwise healthy infants 2 to 4 weeks old. Haemophilus influenzae infections occur primarily in children 6 months to 4 years old.
i. The incidence of this infection has been reduced dramatically because of routine immunizations against the organism.