Affiliations: University Outpatient Clinic, Sports Medicine and Sports Orthopedics, Universität Potsdam, Potsdam, Germany
Correspondence:
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Corresponding author: Michael Rector, University Outpatient Clinic, Sports Medicine and Sports Orthopedics, Universität Potsdam, Am Neuen Palais 10, Haus 12, 14469 Potsdam, Germany. Tel.: +49 0331/977 1768; Fax: +49 0331/977 1296; E-mail:rector@uni-potsdam.de
Abstract: BACKGROUND: The Achilles tendon (AT) requires optimal material and
mechanical properties to function properly. Calculation of these properties
depends on accurate measurement of input parameters (i.e. tendon
elongation). However, the measurement of AT elongation with ultrasound
during maximum voluntary isometric contraction (MVIC) is overestimated by
ankle joint rotation (AJR). Methods to correct the influence of this
rotation on AT elongation exist, yet their reproducibility in clinical
settings is unknown. OBJECTIVE: To evaluate the test-retest reproducibility of AT
elongation during MVIC after AJR correction. METHODS: Ten participants
attended test and retest measurements where they
performed plantar-flexion MVIC on a
dynamometer. Simultaneously, ultrasound recorded AT elongation as the
displacement of the medial gastrocnemius-myotendinous junction, while an
electrogoniometer measured AJR. The ankle was then passively rotated to the
AJR achieved during MVIC and AT elongation again determined. Elongation was
corrected by subtracting this passive AT elongation from the total AT
elongation during MVIC. Reproducibility was evaluated using ICC (2.1),
test-retest variability (TRV, %), Bland-Altman analyses (Bias ± LoA
[1.96*SD]) and standard error of the measurement (SEM). RESULTS: Corrected AT elongation reproducibility exhibited an ICC =
0.79, SEM = 0.2 cm and TRV = 20 ± 19%. Bias ± LoA were
determined to be 0.0 ± 0.8 cm. CONCLUSIONS: Using this ultrasound and electrogoniometer-based
method, corrected AT elongation can be assessed reproducibly.
