Bone Abstracts

Objectives: Previously we have shown in healthy pre-pubertal boys that short periods of whole body vibration (WBV) increased the bone formation marker PINP by 25.1% and resorption marker CTX by 10.9%. The aim of this study was to see if otherwise healthy boys with a history of fracture would respond to WBV in the same way.

Methods: In addition to 11 pre-pubertal boys measured previously in the same way, 20 pre-pubertal boys aged 7-13 years, who were at least 6 months post fracture, were randomised to stand on either the Juvent 1000 (low magnitude, high frequency) or the Galileo Med M (high magnitude, high frequency) platforms for 10 minutes (2.5 minutes × 4 with interspersed 30 second rest periods) on 5 consecutive days. Fasting serum was collected before WBV on D1 and on D8. PINP and CTX were measured using an automated analyser and OPG and sclerostin using manual ELISAs.

Results: PINP and CTX increased from baseline to D8 in the non-fracture boys (n=11; 743 (189) to 894 (277) ng/ml and 1.876 (0.389) to 2.046 (0.506) ng/ml respectively), but did not change in the boys with a history of fracture (n=15; 588 (156) to 578 (172) ng/ml and 1.951 (0.341) to 1.922 (0.467) ng/ml respectively). The differences in %change of P1NP and CTX between the non-fracture and fracture groups were highly significant; mean difference in PINP %change was 23.8% (CI 10.8 to 36.9; independent samples t-test P=0.001); mean difference in CTX %change was 11.8% (CI 1.7 to 21.8; P=0.02). Multivariate analysis including a range of other factors such as body size and physical activity made no difference to the results. There were no significant changes in OPG or sclerostin from baseline at D8 in either group. No difference between platform groups was found.

Conclusions: Boys who have a history of fracture show reduced responsiveness to short periods of WBV compared to non-fracturing counterparts; reduced responsiveness to mechanical stimulation, if present prior to the fracture occurring, and if related to reduced bone accrual, might help explain increased fracture susceptibility in some children.

Disclosure: NJB consults for Alexion, Mereo, UCB and Amgen, and receives grant support for clinical studies from Alexion and Amgen.