Trabecular bone microarchitecture and vibration transmission in ambulatory children with cerebral palsy
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Children with physical disabilities, such as cerebral palsy (CP), have reduced
bone mass and quality, especially in the lower extremities. It is known that low bone
mass is present across all levels of CP, including nonambulatory and ambulatory
children. It is also known that trabecular bone microarchitecture, an important feature
of the skeleton that is an independent predictor of fracture risk, is markedly
underdeveloped in nonambulatory children with more severe forms of CP. However,
the level of underdevelopment in trabecular bone microarchitecture in ambulatory
children with milder forms of CP has not been explored. In addition to gaining a better
understanding of their bone deficit, identifying treatment strategies that increase bone
mass, enhance trabecular bone microarchitecture and reduce fracture risk in children
with CP is imperative.
An obvious approach is to increase their participation in physical activity
because it is lower than typical, even in ambulatory children with milder forms of
CP. However, because of their poor balance and coordination, alternative activities or
treatments for enhancing bone development for children with CP are sought. One
treatment that has received considerable attention during the past 10 years is highfrequency,
low-magnitude vibration (HLV). A handful of studies have shown that
HLV can increase bone mass and enhance bone architecture in children with
CP. However, the effect of HLV at specific bone sites is likely dictated by the degree
to which the HLV stimulus is transmitted. Unfortunately, no studies have examined
the transmission of HLV in children with CP.
The first aim of this dissertation was to determine the degree of
underdevelopment in trabecular bone microarchitecture at the distal tibia and the distal
femur in ambulatory children with CP. The primary finding was that the degree of
underdevelopment in trabecular bone microarchitecture at the distal femur in
ambulatory children with CP was not as marked as the underdevelopment observed in
nonambulatory children with CP (p < 0.05). However, measures of trabecular bone
microarchitecture deviated from control values by ≥ 1 SD (p < 0.05) in both
groups. Furthermore, the degree of underdevelopment in trabecular bone
microarchitecture was more pronounced in the distal tibia than in the distal femur in
ambulatory children with CP compared to typically developing controls with measures
of apparent trabecular thickness lower and apparent trabecular separation higher by ≥
2 SD (p < 0.05).
The second aim of this dissertation was to determine the degree to which the
HLV signal emitted by a floor-based platform transmits across the distal tibia and the
distal femur in ambulatory children with spastic CP during standing. The primary
finding was that relative to the HLV signal emitted at the platform, the signal was
amplified at the distal tibia but dampened at the distal femur in children with CP (p <
0.05). The damping of HLV was related to the degree of spasticity, with greater
spasticity associated with less signal transmission to the distal tibia (r = -0.547, p <
0.05) and distal femur (r = -0.566, p < 0.05).
The third aim of the dissertation was to determine the effect of tissue
composition on HLV transmission in ambulatory children with spastic CP. The
primary finding was that measures of trabecular bone microarchitecture were not
related to HLV transmission in children with CP or typically developing children p >
0.05). Muscle volume in the midleg was inversely related to HLV transmission to the
distal femur in typically developing children (r = -0.626, p ≤ 0.05), but not in children
with CP.
The overall findings from this dissertation provide a greater understanding of
the level of skeletal compromise in ambulatory children with mild CP. They also
provide insight into the degree to which HLV transmits to the primary fracture sites of
children with CP. The findings will help guide future studies aimed at determining the
usefulness of HLV as a treatment for poor bone development in children with CP.