The Sternum's Natural Lifecycle: From Cartilage to Bone
The sternum, or breastbone, is a flat, T-shaped bone located centrally in the chest, connecting the ribs via cartilage to form the front of the rib cage. Its development is a complex process that primarily occurs during childhood and adolescence. Starting as cartilage in utero, the sternum gradually hardens into bone through a process called ossification. This process is not a single event but a progressive series of fusions.
Ossification and Skeletal Maturity
- Fetal Development: The sternum first forms from two mesenchymal bars that fuse in the midline, a process largely complete by the tenth week of pregnancy.
- Childhood: The main body of the sternum consists of segments called sternebrae. These segments remain separated by cartilage for many years after birth.
- Adolescence: Union of the sternebrae begins around puberty and continues, typically fusing completely by age 25. The xiphoid process, the small, pointed tip of the sternum, can remain cartilaginous until age 40 or 60 before fully calcifying.
Once skeletal maturity is reached, the sternum's size is fixed. An adult's sternum will not undergo further growth in length or width under normal circumstances. While some morphological changes may occur up to age 30, these are minor and do not equate to the bone getting bigger.
Understanding Pectus Carinatum: The Case of the Protruding Sternum
When people ask if their sternum can get bigger, they are often referring to a noticeable protrusion of the chest wall. This is typically not due to the sternum bone itself growing larger but is a symptom of a condition called pectus carinatum, also known as "pigeon chest".
The Mechanism Behind the Outward Push
Pectus carinatum is caused by an overgrowth of the costal cartilages—the flexible tissue connecting the ribs to the sternum. This rapid and abnormal growth forces the sternum and ribs outward, creating a prominent ridge on the chest. The deformity often worsens during adolescent growth spurts, making it particularly noticeable during the teenage years. The precise cause is unknown, but a genetic component is suspected, as it can run in families.
Diagnosis and Symptoms
For many, pectus carinatum is primarily an aesthetic issue, affecting self-esteem and body image. In more severe cases, however, it can lead to physical symptoms such as:
- Difficulty breathing during physical activity
- Chest pain
- Fatigue
- Frequent respiratory infections
These symptoms occur because the chest wall rigidity and shape can compress the heart and lungs, impeding their function. It's important to differentiate this condition from normal bone structure variations. A doctor can perform a physical examination to assess the chest wall and determine the nature of the issue.
Pectus Carinatum vs. Pectus Excavatum: A Comparative Table
To better understand chest wall deformities, it's helpful to compare pectus carinatum with its more common counterpart, pectus excavatum (sunken chest). The underlying cause for both is often related to abnormal cartilage growth.
| Feature | Pectus Carinatum (Pigeon Chest) | Pectus Excavatum (Sunken Chest) |
|---|---|---|
| Appearance | Breastbone and ribs protrude outward, creating a bird-like chest. | Breastbone is depressed or sunken inward. |
| Underlying Cause | Overgrowth of costal cartilage pushing the sternum outward. | Overgrowth of costal cartilage pulling the sternum inward. |
| Typical Onset | Most commonly diagnosed during growth spurts in adolescence. | Can be present at birth or develop later. |
| Primary Concern | Often cosmetic, but can cause physical symptoms in severe cases. | Can cause compression of the heart and lungs, affecting function. |
Can Physical Activity Change the Sternum's Appearance?
While weight training and other exercises cannot change the size of your sternum bone, they can alter the appearance of your chest. Building the pectoral muscles around the breastbone can create a fuller, more muscular chest, which can help camouflage a mild protruding sternum. Additionally, improving posture through core and back strengthening can help you stand taller, making your chest look more balanced and less pronounced. However, for a structural deformity like pectus carinatum, exercise alone will not be an effective treatment.
- Does weightlifting make it worse? In most cases, no. Strength training is unlikely to negatively affect a pre-existing pectus carinatum. Some bracing treatments even allow for exercise, though heavy lifting might be restricted immediately after a surgical correction.
- Can it improve symptoms? Physical therapy and targeted exercises can help with breathing mechanics and overall cardiovascular function in individuals with milder deformities.
Medical Options for Treating Sternum Protrusions
For those with significant pectus carinatum, medical intervention can provide correction and relief. Treatment plans are tailored to the patient's age and the severity of the condition.
Non-Surgical Bracing
In younger patients whose skeletons are still flexible, an external compression brace is often the first line of treatment. This custom-fitted brace applies gentle, continuous pressure to the chest wall, gradually reshaping the cartilage and moving the sternum back into a more normal position. The success of bracing depends heavily on the patient's adherence to the wearing schedule, with significant improvement often seen within a year.
Surgical Correction
Surgery is typically reserved for severe cases, older patients whose skeletons are rigid, or those who do not respond to bracing.
- Modified Ravitch Procedure: This is an open surgery that involves making an incision, removing the overgrown costal cartilage, and then repositioning the sternum. A temporary bar may be inserted to hold the sternum in place as the cartilage regrows correctly.
- Abrahamson Technique: This is a less common minimally invasive approach for pectus carinatum correction.
For more information on treatment options for chest wall deformities, you can review the resources provided by Johns Hopkins Medicine.
Seeking Professional Medical Advice
If you or a loved one are concerned about the size or shape of the sternum, it is best to consult a healthcare professional, such as a pediatrician or thoracic surgeon. They can accurately diagnose the condition, determine the cause, and recommend the most appropriate course of action based on your specific circumstances.
Conclusion: The Final Word on Sternum Growth
To be clear, a healthy, mature sternum does not spontaneously get bigger. The perception of an enlarging sternum is nearly always related to an underlying anatomical issue, most notably pectus carinatum, where the cartilage, not the bone, is overgrown. While this condition can be a source of cosmetic concern or, in severe cases, physical discomfort, effective non-surgical and surgical treatments are available. For accurate assessment and treatment, a medical consultation is always the best path forward.
