Bone Abstracts

Objectives: Osteogenesis imperfecta (OI) is a bone fragility disorder associated with reduced muscle size, dynamic muscle function and mobility. This paired randomised controlled pilot study assessed the effect of whole body vibration (WBV) training on bone density and geometry, muscle size and function, mobility, and balance in children with OI.

Methods: Twenty-four children (5–16 years) with OI types 1,4 and limited mobility (defined as a Childhood Health Assessment Questionnaire (CHAQ) score ≥0.13), were recruited in gender- and pubertal stage-matched pairs. Incident fractures in two boys (WBV arm) led to exclusion of two prepubertal male pairs. Matched pairs were randomised to either 5 months of WBV training (3×3 min twice daily) using a rotational WBV device, or regular care. Bone and muscle variables measured by dual-energy X-ray absorptiometry (lumbar spine, hip, total body) and peripheral quantitative computed tomography (distal and proximal tibia). Mobility assessed by six-minute walk tests and CHAQ, and dynamic muscle function by mechanography using single two-leg jumping, multiple one-leg hopping, chair- and heel-rising tests, and balance tests.

Results: At baseline, all participants had reduced six-minute walking distances (median Z-scores −2.34 (−6.51 to −0.58)) and dynamic muscle function (P<0.001). BMI Z-score was associated with higher CHAQ scores (rho 0.552; P=0.005), reduced walking distance and two-leg jumping outcomes (rho −0.405 to −0.533, P<0.05). The WBV and control groups did not differ in the 5-month changes in bone density or geometry. Total lean mass increased more in the WBV group (+1119 g (+224 to +1744)) compared to controls (+635 g (−951 to +1006)), P=0.01, without improving mobility, muscle function or balance.

Conclusion: This first randomised controlled trial in OI children demonstrated that WBV training increased lean mass without changes in dynamic muscle function or bone mass. This suggests reduced biomechanical responsiveness of the muscle-bone unit in OI children and discourages the use of rotational WBV therapy as a tool to increase bone formation in OI. The association of overweight with impaired mobility highlights the need for active weight management in children with OI.

Disclosure: The authors declared no competing interests.