Flail Chest By Thomas G Weiser, MD, MPH, Stanford University School of Medicine Reviewed / Revised Apr 2022 | Modified Sep 2022 View Patient Education Diagnosis Treatment Topic Resources Flail chest Flail chest is multiple fractures in ≥ 3 adjacent ribs that result in a segment of the chest wall separating from the rest of the thoracic cage; it is a marker for injury to the underlying lung.