Cierny’s anatomical classification
The anatomical classification of osteomyelitis is important for understanding and localizing the infection.
Type I (medullary osteomyelitis) diffusely involves the intramedullary cavity, usually after medullary nailing. The entire medullary canal is involved, and will require surgical clearance (nail removal and reaming).
Type II osteomyelitis is superficial, may be present under a plate, but is rarely, if ever, seen with fracture-site infection.
Type III osteomyelitis (localized full-thickness cortical involvement), will require excision of all necrotic bone. During the excision, the full extent of the necrotic area becomes evident. This may weaken the bone, or produce significant dead space. Soft-tissue cover may be inadequate and therefore require reconstruction. Fracture healing may be a problem requiring additional treatment.
Type IV osteomyelitis diffusely involves the entire circumference of a segment of the bone. The entire bone segment must be removed to eliminate necrotic tissue and persistent bacteria.