Effects of Low-level Mechanical Vibration on Bone Density in Ambulant Children Affected by Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a X-linked recessive disorder due to a mutation of the dystrophin gene (Xp21). Dystrophin is a sarcolemmal protein of skeletal and cardiac muscle, and its absence causes progressive muscle degeneration and substitution with fat and connective tissue. The progressive muscle degeneration leads to loss of autonomous walking before the age of 15 years and death for cardiac and/or respiratory failure. There are no specific treatment for DMD, and the standard of care is now based on long-term corticosteroid (CS) use. The studies on bone mass in DMD are very few, but they agree in reporting the presence of a reduced bone mass and an increased rate of fractures probably due to long-term steroid therapy and disuse-osteopenia. The aim of this study, involving 20 ambulant DMD boys (age 7-10 years) has been the evaluation of the effects of low-level mechanical vibrations on bone in a group of ambulant DMD children for 1 year, with RDA-adjusted dietary calcium intake and 25OH vitamin D supplementation.

All children were instructed to have a daily intake of calcium equal to the 100% of the RDA and were supplemented with calcifediol (0.7 mcg/kg/die). The 20 boys were randomly assigned to two groups: group 1 (mechanical intervention group) = a mechanical device (a small platform designed to induce vertical, sinusoidal acceleration) was installed in the home of each boy of group 1. group 2 (placebo control group) = a placebo device was installed in the home of each boy of group 2 All boys were instructed to stand on the platform for 10 minutes each day for 12 months. Compliance was followed and stimulated through weekly telephone contacts with parents and children.