Longitudinal cortical split sign as a potential diagnostic feature for cortical osteitis.

Septic cortical osteitis is a rare but distinct type of bone infection that is characterized as a hematogenously seeded infection predominantly or exclusively limited to the cortex. Diagnosis is difficult and often delayed. Combination of clinical and laboratory findings together with the typical radiological findings consisting of vertically orientated cortical osteolysis, the 'cortical split sign' and the predominantly cortical disruption at the periosteal side of the cortex may lead to the correct diagnosis.