DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY ORIGINAL ARTICLE
Impaired muscle growth precedes development of increased
stiffness of the triceps surae musculotendinous unit in children
with cerebral palsy
MAI CHOE LUND
JENS BO NIELSEN
1 Institute for Neuroscience, University of Copenhagen, Copenhagen; 2 Elsass Institute, Charlottenlund, Denmark; 3 Queensland Cerebral Palsy and Rehabilitation
Research Centre, Child Health Research Centre, Faculty of Medicine, The University of Queensland, Brisbane, Qld, Australia.
Correspondence to Maria Willerslev-Olsen at Elsass Institute, Elsass Fonden, 2920 Charlottenlund, Denmark. E-mail: firstname.lastname@example.org
This article is commented on by Gough page 638 of this issue.
Accepted for publication 24th January
Published online 24th March 2018.
ROM Range of movement
If increased muscle stiffness and contractures in children with cerebral palsy (CP) are
related to impaired muscle growth, reduced muscle growth should precede or coincide with
increased muscle stiffness during development. Here, we compared the volume of the medial
gastrocnemius muscle and the passive (non-neural) stiffness of the triceps surae
musculotendinous unit in typically developing children and children with CP from birth until
4 years of age.
Forty-one children with CP and 45 typically developing children were included.
Freehand three-dimensional ultrasound was used to evaluate the volume of the medial
gastrocnemius muscle. Biomechanical and electrophysiological measures were used to
determine passive and reﬂex mediated stiffness of the triceps surae musculotendinous unit.
Medial gastrocnemius muscle volume increased with the same rate in typically
developing and children with CP until 12 months of age, when a signiﬁcant smaller rate of
growth was observed in children with CP. Passive stiffness of the triceps surae
musculotendinous unit showed a linear increase with age in typically developing children.
Children with CP older than 27 months showed a signiﬁcant increase in passive stiffness.
Reﬂex mediated stiffness was only pathologically increased in four children with CP.
The deviation of medial gastrocnemius muscle volume, earlier than
musculotendinous unit stiffness, is consistent with the hypothesis. The data also point out
that muscle atrophy and muscle stiffness already develops within the ﬁrst 1 to 2 years. This
emphasizes the necessity of early interventions to promote lower limb muscle growth in this
Muscle contractures are a main cause of functional disabil-
ity in children and adults with cerebral palsy (CP).
contractures are characterized by increased stiffness of
muscle and connective tissue, reduced range of joint move-
ment, and altered joint position.
It has been thought that
contractures develop late in childhood as a consequence of
but this view has been challenged by recent
ﬁndings showing that signiﬁcant stiffness of muscle and
connective tissue has already developed at the age of
3 years in children with CP.
Furthermore, range of move-
ment (ROM) in the ankle joint has been found to be
strongly reduced before the age of 4 years and remains
nearly unaltered later in childhood.
reduce spasticity have also been shown to have no effect
on the development of contractures.
hypothesis is that contractures in children with CP may be
related to reduced muscle growth.
A number of studies
have documented that growth of muscles is impaired in
children with CP.
This is, in all likelihood, related to
insufﬁcient muscle use since growth of muscles appear to
follow the trajectory of typically developing children until
around 18 months of age which is shortly after typically
developing children obtain weight bearing and start walk-
Since bones grow rapidly during this period, the idea
is that the relatively lower growth of the muscles gradually
increases the tension on the muscle ﬁbres and stretches the
Muscle, tendon, and connective tissue in
the extracellular matrix undergoes structural changes lead-
ing to increased tissue stiffness and eventually clinically
If this hypothesis is correct,
reduced growth of muscles should precede or coincide with
changes in stiffness and the development of clinically mani-
fested contractures. Here, we used three-dimensional ultra-
sound to measure the volume of the medial gastrocnemius
muscle in typically developing children and children with
CP aged 0 to 4 years. Differences in age-related growth of
672 DOI: 10.1111/dmcn.13729 © 2018 Mac Keith Press