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Intercostal retractions occur when the muscles between the ribs pull inward. The movement is most often a sign that the person has a breathing problem. Intercostal retractions are a medical emergency.
The contraction of the external intercostal muscles causes an elevation of the ribs (inspiratory breathing muscles) whereas both the internal and innermost intercostal muscles lower the ribs (expiratory breathing muscles). Ventrally they are bordered by the external thoracic fascia. 2  Internal intercostal muscles: originate at the upper border of a rib and insert ventrocranially at the lower border of the rib above. 3  Innermost intercostal muscles: separate from the internal intercostal muscles and insert behind the costal grooves.