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Bone X-ray anatomy
Last reviewed: 06.07.2025
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The bones of a living person's skeleton can be studied using X-rays. The presence of calcium salts in bones makes them less "transparent" to X-rays than the soft tissues surrounding them. Due to the uneven structure of bones, the presence of a more or less thick layer of compact cortex, and spongy substance inside it, bones and their parts can be seen and distinguished on X-rays.
The compact substance forms a dense "shadow" on the radiograph in the form of light stripes of greater or lesser thickness, and the spongy substance forms a network-like pattern, in which the cells look like dark spots of various sizes. In the diaphyses of tubular bones, in their middle part, the rather thick compact substance gives a "shadow" of the corresponding thickness, narrowing in the area of the epiphyses, where the compact substance becomes thinner. Between the two light "shadows" of the compact substance, a darker wide stripe is visible, corresponding to the bone marrow cavity. The compact substance of the spongy (short) and epiphyses of tubular bones is represented on radiographs by a narrow (thin) light stripe. Inside this stripe, a mesh of spongy substance is visible, along the direction of the beams of which one can trace the lines of compression and tension. Various types of bone receptacles containing soft tissues transparent to X-rays (for example, the eye sockets) or air-filled cavities (paranasal sinuses, nasal cavity) appear on X-rays as large dark formations ("clearances"), limited by light lines that correspond to their bone walls. Grooves on bones formed as a result of the adjacency of blood vessels (arteries, veins) or sinuses of the dura mater of the brain, appear on X-rays as "clearances" of greater or lesser width - dark lines.
At the points where the bones are connected to each other, a dark strip is noted - the X-ray joint space, limited by lighter lines of compact bone substance that forms the articular surfaces. The width of the X-ray joint space depends on the thickness of the articular cartilage, which is transparent to X-rays. On X-rays, one can see the ossification points and use them to determine the age, trace the replacement of the epiphyseal cartilage with bone tissue, and the fusion of bone parts (the appearance of synostosis).