Anatomy clinical correlates: Thoracic wall

If it wasn't for our thoracic wall, many of the important organs in our thoracic cavity would be unprotected and vulnerable to injury.But sometimes the thoracic wall itself can be injured, which has a wide range of clinical consequences depending on the affected structures.Let’s start by talking about the ribs.First, like any other bone in our body, ribs can break, causing rib fractures.These usually result from direct trauma or crushing injuries.The middle ribs are the ones most commonly fractured.The weakest part of a rib is the posterolateral bend, anterior to its angle.However, direct trauma can cause a rib to fracture anywhere.The broken part of the rib can harm internal organs, such as the liver, kidney or the spleen.Rib fractures higher up can cause mediastinal injuries, and if the fracture is lower, then it can tear the diaphragm.Furthermore, rib fractures at any level have the risk of causing an intrathoracic injury such as a pneumothorax, which is when there’s air in the pleural cavity, and that doesn’t allow the lung on that side to expand properly.Since ribs move during respiration, coughing, laughing and sneezing are very painful after a rib fracture!A related injury is a flail chest, which is when three or more ribs fracture in two or more places, which can allow a big segment of the thoracic wall to move freely.During a normal inspiration, the thoracic wall expands outwards and increases its diameter, whereas during expiration, it decreases its diameter to expel air.However, when there’s a flail chest, the movement is paradoxical, meaning that during inspiration, the free segment actually moves inward and during expiration, it moves outward.This is an extremely painful injury that impairs ventilation, and, as a consequence, blood isn’t properly oxygenated.Management wise, for a flail chest, you want to ensure adequate pain control and supplemental oxygen if needed.If respiratory failure occurs as a result of the flail chest, then positive pressure ventilation can be used to force the flail chest segment out during inspiration.Sometimes, a chest tube may also be required.Now, between the ribs, in the anterior part of the chest, there’s the sternum, which is the protector of the mediastinal viscera.In some situations, however, we may need access to those viscera, like during open heart surgery, or to remove a tumor in the lungs.And that’s when a median sternotomy can be performed, which is when the sternum is split in the median plane and retracted.Retraction is possible because the ribs and costal cartilages are very flexible and allow spreading.And following surgery the two halves are joined together and typically joined using wires or sutures.Another clinical situation involving the sternum is when it doesn’t develop normally.One of them is pectus excavatum or funnel chest, which is when the sternal cartilages grow abnormally, leading to a caved-in or sunken appearance of the anterior thoracic wall due to chest wall depression.This can sometimes be associated with conditions, such as Marfan syndrome, osteogenesis imperfecta, mitral valve prolapse, and Ehlers-Danlos syndrome.If the condition is severe, then it can lead to shortness of breath, fatigue and even compression of the heart.Another sternum abnormality is pectus carinatum or pigeon chest, and in contrast to pectus excavatum this is typically characterized by the sternum protruding outward.This condition is typically asymptomatic, however at the protrusion site there can be tenderness on palpation and individuals can experience tachypnea during intense exercise.This condition is sometimes associated with scoliosis, Marfan syndrome, Noonan syndrome or osteogenesis imperfecta.Quiz time!Which image shows pectus excavatum and which one shows pectus carinatum?Alright, as a quick recap.The middle ribs are the ones most commonly fractured and the weakest part of the rib is just anterior to its angle.A flail chest is when multiple ribs are fractured, allowing a big segment of the thoracic wall to move freely in a paradoxical way.It is initially managed with analgesia and oxygen, but may require positive pressure ventilation and a chest tube.A median sternotomy is useful during heart surgery or to remove a tumor in the lungs.Pectus excavatum is when the chest has a caved-in appearance, while pectus carinatum is when the chest is protruding outward.