Scand J Med Sci Sports. 2018;28:1471–1472. wileyonlinelibrary.com/journal/sms
© 2017 John Wiley & Sons A/S.
Published by John Wiley & Sons Ltd
LETTER TO THE EDITOR
Response to considerations on “Achilles tendinopathy and
patellar tendinopathy display opposite changes in elastic
We thank Wu (2017) and the editors for the opportunity to
provide greater discussion on the association of tendon shear
wave velocity (SWV) with potentially important covariates
including sex and age. We would like to first clarify that we
did not directly compare the Achilles and patellar tendinopa-
thy groups. Instead, the (most) affected tendon from each ten-
dinopathy group was compared with a matched tendon from
the healthy control group. Due to the blinded nature of this
study, we sought to include a broad cohort of healthy con-
trol participants and performed statistical adjustment for age,
sex, body mass index, and tendon thickness in all models.
Although not without limitation, we consider this approach
provides some meaningful information in response to the
comments raised in this letter to the editor.
Wu (2017) postulates that the lower male- to- female pro-
portion might explain the higher SWV for patellar tendinop-
athy compared to healthy controls. Evidence of differences
in tendon mechanical properties between sexes is reported
but not all studies,
derived from measurement
of force and deformation during maximal contraction.
Heterogeneity is also found between studies using shear wave
In our sample, no male- female differences in
SWV were observed at any tendon region, suggesting it did
not have a large impact on our conclusions.
Wu (2017) also postulates that age discrepancy between
groups may explain the opposing changes in elastic proper-
ties between Achilles tendinopathy and patellar tendinopathy.
While we did not find a significant correlation between age
and SWV for any tendon region in our healthy control par-
ticipants, we cannot discount the possibility of type 2 error,
given the sample size and age range of our healthy group
were smaller than previous studies, which report significant
age- related reductions in SWV for the Achilles
Using a multivariate model to test for differences
between Achilles tendinopathy and healthy participants, we
identified that both age and tendinopathy were independent
predictors of SWV of the Achilles insertion. Reduction in
SWV was most pronounced in older adults with Achilles
tendinopathy. The multivariate model for the proximal patellar
tendon identified tendinopathy as the only predictor of SWV.
We acknowledge there is potential for sample bias,
as patellar tendinopathy phenotypically affects young
and Achilles tendinopathy is most common in
middle- aged individuals.
We concur with Wu (2017) that
further research including sex- and age- matched healthy con-
trols is needed to provide more solid evidence that Achilles
tendinopathy and patellar tendinopathy display opposing
trends in tendon elastic properties.
B. K. Coombes http://orcid.org/0000-0002-6163-1047
L. Heales http://orcid.org/0000-0002-4510-3324
F. Hug http://orcid.org/0000-0002-6432-558X
B. K. Coombes
School of Biomedical Sciences, The University of
Queensland, Brisbane, Qld, Australia
School of Health and Rehabilitation Sciences, The
University of Queensland, Brisbane, Qld, Australia
School of Health, Medical and Applied Sciences, Division
of Physiotherapy, Central Queensland University,
Rockhampton, Qld, Australia
Faculty of Sport Sciences, Laboratory “Movement,
Interactions, Performance” (EA 4334), University of Nantes,
Institut Universitaire de France (IUF), Paris, France
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