The gladiolus is the old anatomical name for the body (corpus) of the sternum, the flat bone at the center of your chest. The term comes from the Latin word for a short sword, and the name stuck for centuries because the long, tapering shape of the sternal body loosely resembles a blade. Modern anatomy textbooks almost universally call it the “body of the sternum” or “corpus sterni,” but the word gladiolus still appears in older references, forensic literature, and the occasional radiology report. It is the largest of the sternum’s three parts, sandwiched between the manubrium above and the xiphoid process below, and it plays a surprisingly varied role in medicine, surgery, and forensic science.
Where the Gladiolus Sits and What It Does
The sternum has three segments. The manubrium is the broad, trapezoidal piece at the top, where the collarbones and first pair of ribs attach. Below it sits the gladiolus, a longer and narrower plate that connects to ribs two through seven via strips of costal cartilage along its lateral edges. At the bottom hangs the xiphoid process, a small cartilaginous or bony projection that is the last part to fully harden with age. Together these three pieces form a shield over the heart, great vessels, and a portion of each lung.
The gladiolus accounts for most of the sternum’s length. In an average adult it measures roughly ten centimeters from top to bottom and is slightly wider at its upper end where it meets the manubrium. The anterior surface is fairly flat and sits just beneath the skin and a thin layer of fat, which is why you can feel it easily by pressing your fingertips to the center of your chest. That superficial position is one reason the bone comes up so often in clinical practice: it is easy to reach with a needle for bone marrow sampling, easy to see on a chest X-ray, and, unfortunately, easy to fracture in a frontal collision.
How the Gladiolus Forms Before and After Birth
The sternum does not start as a single bone. In the embryo, two bands of mesenchymal tissue grow toward the midline from either side of the developing chest wall and gradually fuse into a cartilaginous template. Within that template, separate ossification centers called sternebrae appear. Each segment of the sternal body may contain one or two of these centers; when two are present, they preserve traces of the bone’s paired embryonic origin, a reminder that the sternum is fundamentally a midline fusion structure.
After birth, the sternebrae slowly expand and merge. Each center is surrounded by its own growth plate, and the cartilage between adjacent centers converts to bone over many years. Full fusion of the body segments generally wraps up during adolescence and early adulthood, though individual timing varies.
The Joint Between the Manubrium and the Body
The junction between the manubrium and the gladiolus is called the manubriosternal joint, and it creates the palpable ridge known as the sternal angle (or angle of Louis). Clinicians use this landmark constantly: it marks the level of the second rib, which in turn serves as a starting point for counting ribs, locating heart sounds, and positioning a stethoscope.
There has been long-running debate about what kind of joint this actually is. Microscopic analysis of younger adults shows organized collagen fibers and a mix of fibroblasts and chondrocytes arranged in a pattern that characterizes a symphysis, similar in principle to the joint between the two halves of the pubic bone. With age, the tissue changes. Middle-aged specimens show more cell clusters and a breakdown of collagen organization, and in older adults the collagen lamellae largely disappear, suggesting a slow process of degeneration and eventual conversion to bone. Despite that trend, most people never achieve complete bony fusion at this joint; the manubrium and the sternal body usually remain at least partially separate throughout life.
The Xiphoid Tells a Different Story
The xiphoid process, by contrast, does tend to fuse to the bottom of the gladiolus, and it does so on a roughly predictable schedule. Research in Mediterranean populations found that xiphoid fusion typically begins between age 30 and 39 and shows a direct correlation with chronological age, making it one of the more reliable single-bone indicators for forensic age estimation. The manubriosternal joint’s resistance to fusion is what makes the xiphoid stand out: it is the only sternal junction where bony union is the expected outcome rather than a rare event.
Sternal Foramina and Why They Matter
Sometimes the sternebrae do not fuse completely, and the result is a small hole in the bone called a sternal foramen. A large meta-analysis covering over 16,000 subjects found that roughly 9% of people have at least one foramen somewhere in the sternal body or xiphoid process. Foramina in the body alone were present in about 6.5% of subjects, and xiphoid foramina in about 3%. The holes were more common in men than in women (about 12% versus 7%) and showed geographic variation, with higher rates in South American and African study populations than in North American or European groups. The average foramen measured roughly 5 millimeters across.
On imaging, these foramina can look alarming. A tiny round lucency in the sternum on a CT scan could be mistaken for a lytic bone lesion, prompting unnecessary worry about cancer. More concerning is the physical risk during procedures that involve pushing a needle through the sternum. A CT study of patients with known sternal foramina found that the structure sitting directly behind the hole was the lung in more than half the cases and the heart or pericardium in about a fifth. In every patient examined, a needle inserted deep enough would eventually reach the pericardium. There was no relationship between body habitus and the distance to vital organs, so a patient’s size offers no reassurance.
Because of this, clinicians performing sternal bone marrow biopsies or acupuncture over the sternum are advised to screen for foramina beforehand when possible. A foramen transforms a routine needle stick into a potential path to a pneumothorax or cardiac puncture.
Sternal Fractures
The gladiolus is the most common site for sternal fractures. In a radiographic analysis of 200 sternal fractures, about three-quarters were located in the corpus sterni. Traffic accidents dominated, and the vast majority of those involved restrained passengers, meaning the seatbelt itself transmitted the force. Most fractures were nondisplaced or only slightly displaced, but about a quarter showed moderate to severe displacement. Nearly 30% of patients had accompanying thoracic injuries, and spine fractures were found in 13%.
Fractures or disruptions at the manubriosternal junction, though less common (about 8.5% of the total), carried a notably higher rate of concurrent spinal fractures. Displaced fractures in the body of the sternum, meanwhile, were more frequently associated with cardiac and other thoracic injuries. Emergency physicians have argued for a higher index of suspicion for cardiac complications even when the only chest finding is a sternal fracture in a belted driver or passenger, since the mechanism can transmit substantial energy to the heart without leaving external signs on the rest of the chest wall.
Bone Marrow Aspiration From the Sternum
The sternum remains a common site for bone marrow sampling in some countries, particularly when the iliac crest (the hip bone) is not accessible or when a quick bedside sample is needed. The gladiolus is chosen because it lies just under the skin, making needle placement straightforward. But the bone is thin, and the margin for error is measured in millimeters.
Studies using CT measurements have found that the distance from the anterior surface of the sternum to the ascending aorta varies widely. In one Japanese series, the gap ranged from just over 4 millimeters to nearly 48 millimeters in men, with a median around 24 millimeters. In women the range was similar, from about 5 to 38 millimeters, with a median just over 21. A small but meaningful fraction of both men and women, roughly 4% each, had less than 10 millimeters separating the sternum from the aorta. That leaves very little room for a needle to go wrong, which is why depth-limited aspiration needles with adjustable guards are standard equipment for this procedure.
Median Sternotomy and Access to the Heart
For cardiac surgery, the standard approach for decades has been to split the sternum straight down the middle, a procedure called a median sternotomy. The technique was first tested in animals in 1897, when a surgeon named Milton demonstrated that a midline sternal cut could be performed safely in a live goat, which survived the procedure. Milton noted that the exposure of the heart was excellent, and while it took several more decades for the method to become routine in humans, the median sternotomy eventually became the dominant access route for open-heart operations.
After surgery, the two halves of the divided gladiolus need to be brought back together and held in place while they heal. Stainless steel wires have been the traditional closure method, though rigid plate fixation systems are also used. Healing of the sternum takes weeks to months, during which patients are typically told to avoid heavy lifting or pulling motions that could stress the repair. Infection of the sternum after sternotomy, known as sternal osteomyelitis, is a feared complication. Interestingly, a study examining risk factors for this complication found that none of the usual suspects, including diabetes, obesity, long operation times, or extended ventilator use, reached statistical significance as independent predictors, suggesting the condition may be driven by factors that are harder to measure or control.
Sternal Tumors
Primary tumors of the sternum are rare. When neoplastic involvement does occur, metastases from cancers elsewhere in the body are far more common than tumors originating in the bone itself. Among primary sternal tumors, malignant lesions outnumber benign ones. Because of this skew, the general clinical rule is that a mass arising from the sternum should be considered malignant until proven otherwise. Imaging with CT and MRI is used to characterize the lesion and assess whether it has invaded surrounding soft tissues. The rarity of these tumors means that most clinicians will see very few over the course of a career, and treatment decisions often involve referral to specialized centers.
Forensic Uses of the Gladiolus
Forensic anthropologists use sternal anatomy for two main tasks: estimating age at death and estimating sex. The progressive fusion of the sternal segments, the changes at the manubriosternal joint, and the ossification of the xiphoid process all follow broadly age-dependent timelines. Research on autopsy specimens from central India found that the sternum shows significant age-related morphological changes and identifiable fusion patterns that are useful for forensic age estimation, though variability in fusion timing means sternal analysis works best when combined with other skeletal indicators rather than used in isolation.
Sex estimation from the sternum relies on size and proportions. Male sterna tend to be longer and wider than female sterna, and discriminant function analyses built from population-specific measurements can classify sex with reasonable accuracy. The catch is that sternal dimensions vary enough across populations that standards developed in one region do not transfer cleanly to another. A formula derived from Indian autopsy data, for example, may misclassify individuals from a European or East Asian population. This is a recurring challenge in forensic anthropology, and it means that regional reference standards need to be developed and validated independently.
Sternal Shape Across Primates
The shape of the sternum is not constant across primates and reflects differences in how the chest is built and used. Apes, including humans, tend to have broader manubria and wider sterna than monkeys. This fits with the broad, barrel-shaped rib cage characteristic of hominoids, which in turn relates to differences in shoulder mobility and locomotion. A monkey that runs along the tops of branches has a deep, narrow chest and a narrow sternum, while an ape that hangs and swings beneath branches has a wider, shallower chest and a correspondingly broader sternum. In humans, who walk upright and do not brachiate, the wide sternal shape persists as an evolutionary inheritance from our arboreal ancestors, even though the selective pressures that originally drove it have changed.
These comparative differences are more than academic curiosity. Understanding normal sternal variation across primates helps paleoanthropologists interpret fossil fragments, since a partial sternum can offer clues about an extinct species’ body plan and locomotor habits when more informative bones are missing from the fossil record.