Bone health

New measure of bone fragility for young adults with cerebral palsy

Clinicians at Monash Health, Victoria, have shown that a novel measure of bone microarchitecture – trabecular bone score – can give useful clinical insights into bone fragility in adults with cerebral palsy (CP).

Using the measure derived from a two‐dimensional lumbar spine dual‐energy X‐ray absorptiometry (DXA) image they found that more than half the  young adults with CP they assessed had abnormal bone microarchitecture.

The findings confirmed the important role of immobility and muscle function for bone fragility in people with CP, said Dr Anne Trinh and colleagues of the Department of Endocrinology.

Published in the journal Bone, the Monash work also showed that the relatively simple measure of TBS could be used in place of more advanced imaging modalities such as high resolution MRI and peripheral quantitative CT.

The study involved 43 young adults with CP who had evaluable DXA imaging of the lumbar spine between 2005 and 2018. TBS scores were derived by examining the pixel grey level variations in the lumbar spine DXA image.

Of the 43 patients, 22 (51.2%) had low BMD (Z score≤−2) at the lumbar spine. For TBS measures, 16 (37.2%) of the participants had a TBS of 1.23–1.31, representing an intermediate risk of fracture and 8 (18.6%) had a TBS of<1.23, indicating a high risk of fracture.

Of the 22 patients with a low BMD, 6 (27.2%) had TBS values indicating intermediate or high risk of fracture.

The researchers noted that TBS was higher in ambulatory patients and was associated with lean tissue mass, which they said supported a link between immobility, bone microarchitecture and fragility.

They said the high prevalence of poor bone microarchitecture seen in the participants with CP was unsurprising given their multiple risk factors, which also included anticonvulsant use, poor nutrition and hypogonadism.

The study did not show an association  between TBS and fracture rates but that may have been because of the limited sample size, low number of fractures and retrospective study design.

They said TBS appeared to be an attractive tool in assessing bone fragility in CP because it could be done without the need for additional imaging and without further exposure to radiation.

Techniques such as MRI were also challenging for people with CP, often requiring the need for custom splints, stabilising cushions and positioning while in a wheelchair, they noted.

However they said the study was only preliminary and there was a need to further develop TBS cut-offs to reflect fracture risk and validate them in further studies.

“Maintaining muscle function is likely to be important for bone health in young adults with CP and needs to be confirmed in further studies,” they concluded

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