How to request a skeletal survey

For most suspected genetic skeletal dysplasia conditions, a full skeletal survey is required for accurate phenotyping as part of the diagnostic work-up. If genomic testing returns no clear results, the clinical-radiological phenotype can be vital in helping inform further analysis.

This guidance is applicable to both children and adults, though skeletal surveys are usually more informative in children prior to growth plate fusion.

• Skull (anterior-posterior (AP) and lateral), chest, pelvis, spine (AP and lateral), upper limb, lower limb and hand.
• Diagnostic features on foot radiographs are often uninformative, and these images can be included or excluded as per local policy. If a particular foot sign is sought, such films should be specifically requested (for example, hallux valgus in fibrodysplasia ossificans progressiva).
• It is sufficient that one side of the body is imaged for upper and lower limb radiographs, because skeletal signs are often symmetrical. Imaging both sides increases exposure to radiation.

Often, patients already have some of the films required to complete a survey (for example, a chest radiograph). If the film was completed recently, there is no need to repeat it (as a rough guide, films that have been completed within the last year are fine, though if you are unsure you can discuss the case with a radiologist).

Most skeletal dysplasia conditions have an underlying genetic cause, which means that features often manifest early in life. Many skeletal dysplasia conditions cause changes to the growth plate, which fuses at puberty. For that reason, a skeletal survey is most informative in childhood and of least value in adulthood.

Some specific radiological features are only seen at certain times, which means that they require time-sensitive imaging. For example, ‘stippling’ (speckled focal bone calcification) is a key clue in the diagnosis of chondrodysplasia punctata, but is usually only seen under the age of one (though it is sometimes still present at the age of three), so early imaging is key.

However, sometimes it is better to wait. For example, the absence of the patella is a key sign in diagnosing nail-patella syndrome and related patella conditions. The patella ossifies around the age of five, so its absence can only be confirmed in films completed after the age of four. For nail-patella syndrome, an early pelvic film can confirm the diagnosis if posterior iliac horns are present (a pathognomonic sign).

It depends on the exact clinical scenario. Often there is little value in repeating a survey within two years of the previous. If the initial skeletal survey lacked radiological signs, repeat films are unlikely to yield further informative clues unless the clinical examination suggests underlying changes.

However, sometimes radiological features become pronounced with time, so a full survey can be useful. For example, in otospondylomegaepiphyseal dysplasia, the megaepiphyses develop with time and may not be seen until some years have passed.

Meanwhile, the radiological features of other conditions become less pronounced with time, which is also a useful diagnostic clue. For example, in metaphyseal anadysplasia the metaphyseal changes regress or improve with time, which helps confirm the diagnosis. Likewise, in spondylometaphyseal dysplasia corner-fracture type due to FN1 gene changes, the metaphyseal corner fractures ‘heal’ with time, so repeat imaging can be diagnostic. In both these examples, a full skeletal survey repeat is not required – selected images (of lower limbs, for example) are sufficient.

For clinicians

• OMIM: 613073 Metaphyseal anadysplasia 2
• OMIM: 161200 Nail-patella syndrome
• OMIM: 184840 Otospondylomegaepiphyseal dysplasia, autosomal dominant
• OMIM: 215100 Rhizomelic chondrodysplasia punctata type 1
• OMIM: 184255 Spondylometaphyseal dysplasia, corner-fracture type
• Skeletal Dysplasia Group (promotes teaching and research)
• Skeletal Dysplasia Management Consortium: Publications