Low Magnitude Mechanical Loading Is Osteogenic in Children With Disabling Conditions

Authors

  • Kate Ward,

    1. Clinical Radiology, Imaging Science & Biomedical Engineering, University of Manchester, Manchester, United Kingdom
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  • Chrissie Alsop,

    1. Clinical Radiology, Imaging Science & Biomedical Engineering, University of Manchester, Manchester, United Kingdom
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  • Janette Caulton,

    1. The Manchester School of Physiotherapy, Manchester Royal Infirmary, University of Manchester, Manchester, United Kingdom
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  • Clinton Rubin,

    1. Musculo-Skeletal Research Laboratory, Department of Biomedical Engineering, State University of New York, Stony Brook, New York, USA
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  • Judith Adams,

    1. Clinical Radiology, Imaging Science & Biomedical Engineering, University of Manchester, Manchester, United Kingdom
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  • Zulf Mughal

    Corresponding author
    1. Department of Paediatric Medicine, Saint Mary's Hospital for Women & Children, Manchester, United Kingdom
    • Address reprint requests to: Z Mughal, MBChB, FRCP, DCH, Department of Pediatric Medicine, Saint Mary's Hospital for Women & Children, Hathersage Road, Manchester M13 0JH, UK
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  • Dr Rubin served as a consultant for Exogen, Inc., a wholly owned subsidiary of Smith & Nephew Orthopaedics Inc., and is an inventor of the technology. All other authors have no conflict of interest.

Abstract

The osteogenic potential of short durations of low-level mechanical stimuli was examined in children with disabling conditions. The mean change in tibia vTBMD was +6.3% in the intervention group compared with −11.9% in the control group. This pilot randomized controlled trial provides preliminary evidence that low-level mechanical stimuli represent a noninvasive, non-pharmacological treatment of low BMD in children with disabling conditions.

Introduction: Recent animal studies have demonstrated the anabolic potential of low-magnitude, high-frequency mechanical stimuli to the trabecular bone of weight-bearing regions of the skeleton. The main aim of this prospective, double-blind, randomized placebo-controlled pilot trial (RCT) was to examine whether these signals could effectively increase tibial and spinal volumetric trabecular BMD (vTBMD; mg/ml) in children with disabling conditions.

Materials and Methods: Twenty pre-or postpubertal disabled, ambulant, children (14 males, 6 females; mean age, 9.1 ± 4.3 years; range, 4–19 years) were randomized to standing on active (n = 10; 0.3g, 90 Hz) or placebo (n = 10) devices for 10 minutes/day, 5 days/week for 6 months. The primary outcomes of the trial were proximal tibial and spinal (L2) vTBMD (mg/ml), measured using 3-D QCT. Posthoc analyses were performed to determine whether the treatment had an effect on diaphyseal cortical bone and muscle parameters.

Results and Conclusions: Compliance was 44% (4.4 minutes per day), as determined by mean time on treatment (567.9 minutes) compared with expected time on treatment over the 6 months (1300 minutes). After 6 months, the mean change in proximal tibial vTBMD in children who stood on active devices was 6.27 mg/ml (+6.3%); in children who stood on placebo devices, vTBMD decreased by −9.45 mg/ml (−11.9%). Thus, the net benefit of treatment was +15.72 mg/ml (17.7%; p = 0.0033). In the spine, the net benefit of treatment, compared with placebo, was +6.72 mg/ml, (p = 0.14). Diaphyseal bone and muscle parameters did not show a response to treatment. The results of this pilot RCT have shown for the first time that low-magnitude, high-frequency mechanical stimuli are anabolic to trabecular bone in children, possibly by providing a surrogate for suppressed muscular activity in the disabled. Over the course of a longer treatment period, harnessing bone's sensitivity to these stimuli may provide a non-pharmacological treatment for bone fragility in children.

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