The xiphoid process is the smallest and lowest segment of the sternum, or breastbone. Most people remain unaware of its existence until they experience unexpected pain or sensation in the center of their lower chest. This structure is typically thin and pointed, resembling a sword, which is the origin of its name from the Greek word xiphos.
Location and Structure
The xiphoid process typically aligns with the T9 or T10 vertebral level in the back. In most adults, this structure is small, measuring approximately one to two inches (2 to 5 centimeters) in length, though its exact shape can vary significantly. It may be bifid, perforated with a small hole, or curved without functional consequence.
This part of the sternum undergoes a significant developmental change throughout a person’s life. In infants and young children, the xiphoid process is composed entirely of hyaline cartilage, making it soft and flexible.
Full ossification of the xiphoid process often does not complete until a person reaches their 40s. It fuses with the main body of the sternum through a fibrous joint, and this eventual hardening into bone contributes to its rigidity in later life.
Physiological Role
The primary function of the xiphoid process is to act as an attachment site for several muscles that affect both respiration and core stability. It serves as an origin point for muscle fibers of the diaphragm, the dome-shaped muscle beneath the lungs.
In addition to its role in breathing, the xiphoid process provides an insertion point for major abdominal muscles. These include the rectus abdominis, commonly known as the “abs,” and the internal and external oblique muscles. These muscle attachments help stabilize the trunk and contribute to movements like flexing and compressing the abdomen.
Beyond its muscular attachments, the xiphoid process acts as an anatomical landmark for medical professionals. Its location helps guide procedures, such as determining the correct site for abdominal incisions or locating structures during surgery.
Why the Xiphoid Process Causes Concern
Pain localized to this area is medically termed Xiphodynia or Xiphoidalgia. This pain, which can be sharp or dull, often results from inflammation of the xiphoid process or the surrounding cartilage and tissues. The discomfort may worsen with actions like bending, lifting, or deep breathing, and it can sometimes radiate to the chest, abdomen, or even the throat and arms.
Xiphodynia is caused by trauma, such as a direct blow to the chest, or from repeated strain due to heavy lifting or poor posture. Since the pain is located in the lower chest and upper abdomen, symptoms are sometimes mistakenly attributed to more serious conditions like cardiac issues or gastrointestinal problems.
The natural process of ossification, the hardening of the cartilage into bone that occurs with age, can also cause concern. As the soft cartilage turns rigid, people may suddenly feel a hard, unexpected lump that they mistake for an abnormality or growth.
The xiphoid process is a major consideration during Cardiopulmonary Resuscitation (CPR). For chest compressions to be effective and safe, they must be administered on the lower half of the sternum, specifically avoiding the xiphoid process. Incorrect hand placement during CPR can fracture or dislodge the xiphoid process, posing a serious risk of puncturing underlying organs like the liver or diaphragm. Recognizing the xiphoid process as a landmark is crucial for both bystanders and medical personnel during emergency situations.