Suppuration

By the second or third day pus forms at the focus of infection.

The pus is able to penetrate cortical bone and form a subperiosteal abscess. Infection may track up and down the shaft of the bone.

The abscess may extend into:

• the surrounding soft tissue and eventually exit through the skin
• an adjacent joint:
  • this is only possible in the adult if the metaphysis is within the capsule
  • in the neonate the abscess can cross the growth plate and drain into the joint

Vertebral infection may cross the end-plate and the adjacent disc into the next vertebra.