Anatomy of the sternum

The sternum is a long, flat bone that protects the muscles, organs, and vital arteries below the chest. This includes the lungs, heart and stomach, with all their complex blood vessels, muscles and cartilage. The sternum also acts as a connecting structure for the ribs on the sides of the body.

Because part of the sternum sits directly above the heart, this bone sometimes breaks during cardiopulmonary resuscitation (CPR). The sternum must be cut open during heart surgery, including open-heart surgery, making recovery from this surgery more intensive than most other surgeries.

anatomy

The sternum is about 6 inches long and consists of three main parts:

  • Manubrium: wide rectangular section at the top
  • Body: The long, flat part that makes up most of the sternum
  • xiphoid process: A small point at the end of the sternum, noticeably narrower and thinner than the rest of the sternum, made of cartilage that gradually becomes bone until age 40

Since the rectangular section at the top resembles a handle, the entire sternum is likened to an upside-down sword. The rest of the sternum is flat and long, resembling a blade of a sword, ending in what looks like a xiphoid process.

Anatomical variations of the sternum include different sized sternum angles. This usually has little effect on function or treatment after injury, but may vary from individual to individual, such as the presence of a double-barreled xiphoid process and a sternal foramen. The sternum foramen is the separation between the two sides of the sternum and is the result of dysplasia. The hole appears as a small tunnel in the sternum, which doctors often mistake for trauma.

READ ALSO:  Anatomy of the ilium

Function

The sternum joins the first six ribs in the middle of the chest, while serving as a powerful protector for the stomach, heart, and lungs below. The xiphoid process in particular serves as the insertion point for the diaphragm, rectus abdominis and transversus abdominis tendons.

The sternum does not aid any visible range of motion of the chest or torso. However, cartilage connectors between the sternum and each of the upper six ribs facilitate the tiny movements that occur with each breath. Each inward breath requires the lungs to fill with air and the intercostal (or rib) muscles to contract. All of these actions require some interior space to function properly.

Related conditions

In addition to a possible rupture during CPR, other accidents, injuries, and illnesses—even acid reflux—can cause pain or damage to the sternum.

fracture

One of the most common diseases affecting bones is a fracture, and the sternum is no exception. A fractured sternum can cause swelling and pain when breathing, coughing, or laughing, along with difficulty breathing.Fractures of the sternum are also common, and each arm movement causes the bone to wear down.

Learn more about fractures

xiphoid fracture

Due to the marked difference in size and strength of the xiphoid process compared to the rest of the sternum, there is a safety risk during CPR when it is at risk of being fractured.

READ ALSO:  Anatomy of the Kidney

In this life-saving effort, the person providing CPR may not know if a fracture has occurred. Continuing CPR after a xiphoid process rupture can cause this sharp part of the sternum to penetrate one of the underlying organs, which can lead to damage to the liver, spleen, heart, and/or diaphragm.

costochondritis

When the rib cartilage, which is attached to the sternum, becomes inflamed, the pain can be localized in the sternum area and, in severe cases, spread to the arm or shoulder.

Costochondritis can cause severe tingling and tenderness in any of the first three ribs. Redness and warmth in the sternum and rib area may also be noticed.

Digestive and breathing problems

Heartburn, stomach ulcers, and gastroesophageal reflux disorder (GERD), also known as acid reflux, can cause pain in the sternum area if left untreated. Lung disease can occur, such as:

  • pneumonia
  • bronchitis
  • Inflamed pleura

These can cause sternum pain and difficulty breathing.

Damage from other injuries

Scapula (scapula) injuries, clavicle (clavicular) injuries, or hernias can also affect the sternum. The top of the sternum connects to the collarbone to allow normal range of motion and muscle use.

Injury to the collarbone may cause the sternum to swell, pain, pop, or click with vigorous exercise. Hernias or muscle strains in the chest and trunk muscles can cause pain, bruising, and tenderness in the sternum area.

READ ALSO:  Anatomy of the superficial peroneal nerve

These symptoms can also affect someone’s ability to breathe, causing limited mobility and pain in the sternum area.

treat

Most fractures must follow a specific rehabilitation program. However, sternum fractures are an exception because they do not contribute to direct, gross range of motion. The treatment option for a sternum fracture is to control the pain and allow for rest to promote healing.

Fractures of the sternum usually take up to three months to heal, and the level of pain decreases after that. The prognosis for functional recovery after a sternum fracture is excellent because it is fairly straightforward to immobilize the bone with so little functional movement. One of the main, very serious complications that can result from a sternum fracture is an infected incision.

Sternal precautions include limiting weight and limiting arm movement. Some of the main ways to maintain your sternum include keeping a pillow in front of your chest when you cough, not lifting heavy objects, getting up from a chair with your legs, stretching your shoulders, and not getting up with your arms. These instructions all reduce stress and strain on the abdominal muscles and sternum.

Because sternum fractures often occur after a traumatic event such as a major car accident or blunt trauma to the body, other injuries are often repaired at the same time. However, if you have no other injuries that require hospitalization, you can successfully recover from a broken sternum in the comfort of your own home.