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Numerous artefacts can masquerade as fractures, and knowledge of these can avoid erroneous diagnosis.

Mach lines describe enhanced edge perception: a dark edge appears darker and a light edge lighter than expected from optical density alone. They are thought to be caused by lateral inhibition of retinal receptors.

The Uberschwinger artefact (overshoot or rebound effect) is an artefact of DR. The basis of digital image processing involves mathematical manipulation of the image. Unsharp masking is used to obtain pixel values that are closer together when faced with structures with large differences in density, such as orthopaedic devices and bone, so they both can be viewed with one lookup table. The processing causes edge enhancement that gives the radiograph high contrast and edge definition. However, fine detail around metallic implants is lost, and noise increases creating a stripe of reduced density parallel to the interface between the two dissimilar densities [5, 6]. Failing to understand this can lead to incorrect conclusions of osteolysis, implant loosening or infection.

Fascial planes are more radiolucent than muscle, and if superimposed on bones can create an artefact but it is usually clear that this extends beyond the bone margins.

Both poor and absence of packing of solar frog clefts and sulci can be detrimental to interpretation. Radiolucent lines should be scrutinized carefully to determine if they remain within the bone or extend beyond osseous margins. If this is inconclusive, then radiographs can be repeated following repacking and/or without packing. Alternatively, differing degrees of obliquity of the incident X‐ray photon beam will either project the artefact away from the bone or confirm that a radiolucent line remains with the bone.

New bone production can create the appearance of a relative decreased opacity in the adjacent bone.

A range of normal anatomic features can be mistaken for fractures. The fibrocartilage between the distal lateral radius and lateral styloid process (phylogenetic ulna) which is radiolucent for an inconstant period is a common example. Physes can also be variable in appearance, but usually they are bilaterally symmetric. Nutrient foramina are tunnels in the cortices of long bones which house blood vessels coursing to and from the medullary cavity [7, 8]. Position can be variable but size, uniformity of the adjacent bone and trajectory help to distinguish from a fracture (Figure 5.3).

Prominent parallel‐sided bone trabeculae can, on first assessment, give the illusion of a fracture. Careful scrutiny and magnification of the image will demonstrate a slightly meandering course and no interruption of the trabecular lines.

Distinguishing suture lines in the cerebral and visceral cranium from fractures can be challenging. Good anatomic knowledge and reference to an anatomic specimen are important. The spheno‐occipital suture can pose difficulties. It remains visible up to five years of age [9], can be up to three times wider ventrally than dorsally [10] and when a fracture is present there may be limited displacement leading to a false negative.