Redefining the costal margin: A pilot study.

Background: Classical teaching of rib anatomy contends that the false ribs (7th to 10th) fuse anteriorly to form the costal margin of the chest. Slipped rib syndrome consists of false rib subluxation into the thorax with symptomatic impingement of the intercostal nerve. We sought to determine the incidence of this anatomic finding through anatomic study of the costal margin.