The reduction of tibia trabecular density is significantly accelerated in boys with Duchenne muscular dystrophy (DMD) who have lost their independence to ambulate, according to a study published in Bone.
“Currently there is no cure for DMD but the quality of life of affected boys can be improved by medical treatment and supportive care,” the researchers commented. Glucocorticoids, for example, can extend the ability to ambulate by 2 to 5 years.
Regardless of the treatment used, what happens to bone strength when DMD patients start to lose their ability to ambulate?
Crabtree et al decided to conduct a study to answer this question. They conducted a longitudinal observational study of 36 boys with DMD and controls over a 2-year period. The treating neuromuscular consultant of each DMD participant had control over if and when glucocorticoid therapy was initiated.
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The boys were categorized into 3 groups: those retaining the ability to ambulate during the study, those who lost the ability to ambulate independently during the study, and healthy boys.
The results demonstrated that, over time, the most significant differences were between healthy boys and boys with DMD. For both DMD patients who retained their ability to ambulate and those who did not, the highest levels of change could be observed in the cortical bone of the tibia. The results were even more marked as ambulation decreased.
“The most strikingly significant difference was in trabecular bone density for boys who became non-ambulant,” the research team wrote. After 2 years, nonambulant boys had 53% less trabecular bone density at the distal tibia than their healthy, age-matched peers. In comparison, boys who remained ambulant had 27% less trabecular bone density, the team reported.
This means that regardless of their ability to ambulate, boys with DMD had significantly weaker bones compared to age-matched peers without DMD.
“Since this study highlights the dramatic loss of bone density with loss of ambulation it is likely that functional assessment can help identify the point at which medical intervention to strengthen bones should be considered,” the research team concluded.
Crabtree NJ, Roper H, Shaw NJ. Cessation of ambulation results in a dramatic loss of trabecular bone density in boys with Duchenne muscular dystrophy (DMD. Bone. 2021;116248. doi:10.1016/j.bone.2021.116248