Ribs

There are 12 pairs of ribs, one on each side. All twelve of them articulate with the vertebral column. The first seven ribs connect directly to the sternum via cartilage processes (cartilago costalis) and are called true ribs (costae verae). The remaining lower five pairs of ribs are called false ribs (costae spuriae). The 11th  and 12th ribs (costae fluctuantes) do not connect with the cartilaginous arch.

The 3rd to 10th ribs have a typical shape. The wedge-shaped head of the rib (caput costae) has two articular surfaces (facies articulares capitis costae). The tubercle of the rib (tuberculum costae) has one articular surface (facies articularis tuberculi costae). The intercostal vein, artery, and nerve (V-A-N) run in close proximity to the costal groove (sulcus costae). An invagination facilitates contact with the rib cartilage at the ventral end of the body of the rib (corpus costae).

The 1st, 2nd, 11th, and 12th ribs have an atypical rib structure. The 1st rib (costa prima) is hidden under the clavicle and is not palpable. It is broad, stumpy, with the strongest curving, and has only one articular surface on the head. The 2nd rib (costa secunda) is the first palpable rib. It displays only an outline of the costal groove (sulcus costae) and the tuberosity for serratus anterior (tuberositas musculi serrati anterioris) – the origin of the serratus anterior muscle (musculus serratus anterior). The heads of the 11th and 12th ribs have only one articular surface. They do not connect with the costal arch and have no tubercle (tuberculum costae).

Rib cage

Available at: http://www.medicalook.com/systems_images/Rib_cage_large.jpg (Accessed: 13 November 2019).

Intercostal space

Available at: https://www.memorangapp.com/flashcards/75027/Cardiovascular+and+Thoracic+Anatomy/ (Accessed. 19 November 2019).

Rib fracture

Rib fractures are common and may be associated with traumatic injuries such as pneumothorax, hemothorax, or intra-abdominal injury in case of lower rib fractures. Rib fractures occur when a significant amount of force directed at the rib causes a break. Any rib fracture should warrant a thorough evaluation of any concomitant injury, including lungs, heart, kidney, spleen, liver, and neuro-vasculature.

Rib fractures can be traumatic or atraumatic. Most rib fractures are due to direct penetrating or blunt trauma to the chest. The 1st to 3rd ribs are the hardest to break and signify a significant degree of trauma if fractured. The 4th to 10th ribs are typically the most vulnerable, while the 11th and 12th ribs are more mobile and, therefore, more difficult to break. In the elderly, falls are a common etiology of rib fractures and are associated with higher mortality and morbidity than with younger patients. Rib fractures may also be pathologic as a result of cancer metastasis from other organs. Athletes can develop rib fractures with chronic use through repetitive stress and microtrauma. Spontaneous rib fractures can also occur due to severe cough and are more likely to occur in those with osteoporosis or underlying lung disease. Because children tend to have more elastic ribs than adults, children are less likely to sustain rib fractures. Therefore, a child with rib fractures is a sign of significant trauma and should warrant an investigation of possible child abuse.

Rib stress fracture

Available at: https://bjsm.bmj.com/content/bjsports/51/14/1093/F3.large.jpg (Accessed: 13 November 2019).

Most isolated rib fractures are diagnosable through a clinical exam. Typically, patients will provide a history of recent blunt or penetrating thoracic trauma and pain at that site. They may also exhibit decreased ability to perform full inspiration due to pain. The physical exam may reveal chest wall bruising, along with bony tenderness to palpitation or crepitus. Any vital sign abnormalities such as hypoxia, tachypnea, or significant respiratory distress should undergo further evaluation of other possible injuries such as pneumothorax, hemothorax, cardiac, and pulmonary contusions. You should assess kidneys, liver, and spleen with lower rib segment injuries. Any patient with paradoxical chest wall movement or suspicion for multiple rib fractures should be evaluated for flail chest and managed accordingly.

Rib fractures can be diagnosed clinically based upon history and physical exam without imaging. Dedicated rib x-ray series are typically not necessary due to the benign clinical course of isolated rib fractures. If there is suspicion for multiple rib fractures or significant trauma with underlying organ damage, imaging can be the next step. However, chest radiographs are limited and can only diagnose about 50% of isolated rib fractures. Point-of-care ultrasonography can reliably detect rib fractures along with complications of rib fractures such as pneumothorax or haemothorax. A chest computed tomography (CT) scan is the gold standard for detecting rib fractures, although the fractures detected may not be clinically significant. The utility of chest CT during evaluation is of greater importance in the general assessment of trauma for other injuries.

 

 

ULTRASOUND EXAMINATION

The sensitivity of ultrasound in detecting rib fractures is high (78-80%), and the technique is superior to other imaging methods.

The linear probe should be in line with the long axis. The fracture is seen as an interruption of the hyperechoic smooth cortex that widens with respiration. Some fractures can show a hematoma around the fracture area.

Ultrasound examination video

Rib fracture PAME Maribor

Opening and closing of the fracture with respiration

Available at: https://www.acep.org/sonoguide/Images/MSKRibs/msk_ribs_video1(sm).jpg (Accessed: 13 November 2019).

Sternum

The manubrium (manubrium sterni) is a quadrangular-shaped bone with four borders. The suprasternal notch (jugular notch) is at the superior segment of the manubrium. On either side, the left and right clavicular notches are present. The clavicular notches of the sternum articulate with the medial end of each clavicle to form the sternoclavicular joints. The manubrium also articulates with the costal cartilages of the 1st pair of ribs.

The body of the sternum (mesosternum) is the longest part of the sternum. It is flat with depressed ridges along the sides where the costal cartilages of the 3rd to 7th pairs of ribs articulate inferior to the sternal angle.

The sternal angle is where the body of the sternum joins the manubrium. The identification of the sternal angle is a useful anatomical landmark because the costal cartilages of the 2nd pair of ribs attach to the sternum at this site.

The xiphoid process (xiphisternum/xiphoid) is triangular and forms the distal-most part of the sternum. The size and shape of the xiphoid process are highly variable. It is mostly cartilaginous until the age of 40 and becomes completely calcified by the age of 60. However, these age-related changes in the adult xiphoid process are also highly variable.

The sternal angle is the projection formed by the junction between the manubrium and the body of the sternum. These two parts of the sternum lie in slightly different planes causing angulation. This angle corresponds anteriorly to the intervertebral disc between the 4th and 5th thoracic vertebrae. This angle is also known as the angle of Louis.

The sternum’s primary function is to protect the underlying mediastinum and its contents from injury.

Sternum anatomy

Available at: https://1.bp.blogspot.com/-w1ZRYattC8M/XHbfuoUZ2LI/AAAAAAAAHhg/TG1cQndqSuUQGKyOkL10luT4mZili3bGQCLcBGAs/s1600/Sternum.jpg (Accessed: 13 November 2019).

Normal adult sternum (longitudinal composite view). (1) Jugular notch; (2) manubrium; (3) sternomanubrial junction (4) ridge at the level of 3rd costal cartilage (5) ridge at the level of 4th costal cartilage (6) xiphisternum

Available at: https://www.researchgate.net/figure/Ultrasound-of-normal-adult-sternum-longitudinal-composite-view-The-anterior-cortex-has_fig3_291097571 (Accessed: 13 November 2019).

Sternomanubrial and xiphisternal joint can mimic sternal fracture

Available at: https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/august-2017/tips-amp-tricks-sternal-fractures-diagnosed-by-pocus/ (Accessed: 13 November 2019)

Sternal fractures

Sternal fractures are associated with deceleration injuries and blunt anterior chest trauma (an incidence of 3-6.8% in motor vehicle collisions). Mechanisms of injuries associated with sternal fractures are classified into either direct or indirect trauma. Direct trauma includes deceleration injuries and blunt anterior chest trauma. The introduction of seat-belt legislation and shoulder restraints have resulted in an increased frequency of these injuries. Direct impact sports, vehicle-to-pedestrian collisions, falls, and assaults account for the majority of the remaining cases. Indirect forces may cause insufficiency fractures, stress fractures, and pathological fractures. Insufficiency fractures occur spontaneously in patients with severe thoracic kyphosis and in those with osteoporosis. Elderly patients, post-menopausal women, and patients on long-term steroid therapy are at particular risk. Stress fractures have also been noted in athletes who undertake repetitive upper body exercises without a history of acute trauma.

Anterior chest wall pain is typically present with sternal fractures. Shortness of breath has been reported in up to one-fifth of cases. Deep breathing and coughing may aggravate pain. The pain reported in sternal stress fractures or acute insufficiency fractures may mimic other serious medical conditions as there is no obvious mechanism of injury, and the pain is typically more diffuse. Point tenderness over the sternum is frequently present in sternal fractures. Soft tissue swelling, ecchymoses, or palpable deformity may also be present in approximately half of the reported cases. Fracture-related crepitus may be present upon palpation. Assessment for other associated injuries is critical, including rib fractures, flail chest, sternoclavicular dislocation, pneumothoraces, hemothoraces, cardiac tamponade, myocardial contusion, pulmonary contusion, intra-abdominal injuries, spinal compression fractures, as well as other traumatic injuries.

Chest radiographs are often used for imagining, but they have low sensitivity and specificity. The ultrasound offers better performance (sensitivity: 91%). Sternal fractures can be detected in a short amount of time when the examiner is skilled.

 

ULTRASOUND EXAMINATION

The probe should be parallel to the long axis of the sternum. Start scanning at the point of maximal tenderness as this often corresponds to the fracture site. Do not apply too much pressure on the sternum while scanning.

The fracture is seen as a disruption or step off in the echogenic cortex on the ultrasound.

Note that sternomanubrial or xiphisternal joint can mimic fractures.

Sternal fracture

Available at: https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/august-2017/tips-amp-tricks-sternal-fractures-diagnosed-by-pocus/ (Accessed: 13 November 2019).

Sternomanubrial and xiphisternal joint can mimic sternal fracture

Available at: https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/august-2017/tips-amp-tricks-sternal-fractures-diagnosed-by-pocus/ (Accessed: 13 November 2019).

Close up image of sternal fracture6

Available at: https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/august-2017/tips-amp-tricks-sternal-fractures-diagnosed-by-pocus/ (Accessed: 13 November 2019).

Resources

American College of Emergency Physicians. Available at: https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/august-2017/tips-amp-tricks-sternal-fractures-diagnosed-by-pocus/ (Accessed: 13 November 2019).

FOAMcast. Episode 36 - Rib and sternal fractures. Available at: https://foamcast.org/2015/10/21/episode-36-rib-and-sternal-fractures/ (Accessed: 13 November 2019).

Rib Fracture. In StatPearls. Available at: https://www.ncbi.nlm.nih.gov/books/NBK541020 (Accessed: 13 November 2019).

Paulsen F., Wasche J. Sobotta-Atlas of Human Anatomy, General anatomy and musculoskeletal system. 2013. Naklada Slap Altalib, A. A., & Menezes, R. G. (2019). Anatomy, Thorax, Sternum. In StatPearls [Internet]. StatPearls Publishing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK541141/ (Accessed: 13 November 2019).

American College of Emergency Physicians. Available at: https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/august-2017/tips-amp-tricks-sternal-fractures-diagnosed-by-pocus/ (Accessed: 13 November 2019).

Bentley, T. P. and Journey, J. D. (2020) Sternal Fracture, StatPearls. StatPearls Publishing. Available at: http://www.ncbi.nlm.nih.gov/pubmed/29939567 (Accessed: 28 June 2020).

FOAMcast. Episode 36 - Rib and sternal fractures. Available at: https://foamcast.org/2015/10/21/episode-36-rib-and-sternal-fractures/ (Accessed: 13 November 2019).

Khoriati, A. A., Rajakulasingam, R. and Shah, R. (2013) ‘Sternal fractures and their management’, Journal of Emergencies, Trauma and Shock. Wolters Kluwer -- Medknow Publications, pp. 113–116. doi: 10.4103/0974-2700.110763.

Turk, F., Kurt, A. B. and Saglam, S. (2010) ‘Evaluation by ultrasound of traumatic rib fractures missed by radiography’, Emergency Radiology. Emerg Radiol, 17(6), pp. 473–477. doi: 10.1007/s10140-010-0892-9.