Abstract
Background
Ultrasonography has been widely applied for in vivo measurements of tendon mechanical
properties. Assessments of human Achilles tendon mechanical properties have received
great interest. Achilles tendon injuries predominantly occur in the tendon region
between the Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous
junction i.e. in the free Achilles tendon. However, there has been no adequate ultrasound
based method for quantifying the mechanical properties of the free human Achilles
tendon. This study aimed to: 1) examine the mechanical properties of the free human
Achilles tendon in vivo by the use of ultrasonography and 2) assess the between-day
reproducibility of these measurements.
Methods
Ten male subjects had the Achilles tendon moment arm length, Achilles tendon cross
sectional area and free Achilles tendon length determined. All subjects performed
isometric plantarflexion ramp contractions to assess between-day reproducibility on
two separate days. Simultaneous ultrasonography based measurements of Achilles-soleus
myotendinous junction and Achilles-calcaneus osteotendinous junction displacement
together with Achilles tendon force estimates yielded free Achilles tendon mechanical
properties.
Findings
Free Achilles tendon maximal force, deformation and stiffness were 1924 (SD 229) N,
2.2 (SD 0.6) mm and 2622 (SD 534) N/mm on day 1. For between-day reproducibility there
were no significant differences between days for free Achilles tendon mechanical properties.
The between-day correlation coefficient and typical error percent were 0.81 and 5.3%
for maximal Achilles tendon force, 0.85 and 11.8% for maximal Achilles tendon deformation
and 0.84 and 8.8% for Achilles tendon stiffness respectively. Last, osteotendinous
junction proximal displacement on average contributed with 71 (SD 12) % of proximal
myotendinous junction displacement.
Interpretation
This study, for the first time, presents an ultrasonography based in vivo method for
measurement of free AT mechanical properties. The method is applicable for evaluation
of free human Achilles tendon mechanical properties in relation to training, injury
and rehabilitation.
Keywords
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Article info
Publication history
Published online: March 10, 2011
Accepted:
February 17,
2011
Received:
November 16,
2010
Identification
Copyright
© 2011 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
