Abstract
Purpose
Elongation of the Achilles tendon has been associated with poorer function in patients treated for ruptures. This has led to the development of various ultrasound-based measurements, and the purpose of the present study was to compare the reliability of three ultrasound-based measuring procedures.
Methods
Twenty healthy individuals (40 tendons) were assessed by two testers at two occasions, 12 weeks apart. The tendon length was measured from the calcaneal insertion to the mid-sagittal muscle tendon junction (MTJ) using skin markings or extended-field-of-view (EFOV) imaging, or from the calcaneal insertion to the distal medial MTJ using skin markings. Test–retest and inter-tester reliability as well as side-to-side length differences were assessed for all three procedures.
Results
Test–retest intraclass correlation coefficients (ICCs) for measurements from the mid-sagittal MTJ using EFOV imaging and skin markings, and from the distal medial MTJ using skin markings were 0.83, 0.90 and 0.96 for tester 1 and 0.87, 0.91 and 0.96 for tester 2, respectively. The corresponding inter-tester ICCs were 0.85, 0.91 and 0.96. Side-to-side lengths were significantly different for measurements from the mid-sagittal MTJ and the distal medial MTJ using skin markings, with mean differences of 0.3 and 0.4 cm, respectively.
Conclusions
Test–retest and inter-tester ICCs were excellent for all three measuring procedures, however, the use of skin markings provided consistently better agreement and reliability compared to EFOV images. The best agreement and highest ICCs were achieved for measurements from the distal medial MTJ, but side-to-side length differences warrant caution when contralateral measurements are used to evaluate tendon elongation.
Level of evidence
III.
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Contributions
EFB contributed to the design of the study, collection of data and drafting and revising the manuscript. SM contributed to the design of the study, collection and analysis of data and revising the manuscript. JSB contributed to analysis of data and drafting and revising the manuscript. SEH contributed to the design of the study, collection and analysis of data and drafting and revising the manuscript.
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The authors declare that they have no competing interests.
Ethical approval
The study was approved by the Regional Committee for Medical and Health Research Ethics (reference 2014/2202), and by the data protection official at the Akershus University Hospital (reference 15-032).
Funding
The study received internal funding from Akershus University Hospital (Grant 265926).
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Brouwer, E.F., Myhrvold, S.B., Benth, J.Š. et al. Ultrasound measurements of Achilles tendon length using skin markings are more reliable than extended-field-of-view imaging. Knee Surg Sports Traumatol Arthrosc 26, 2088–2094 (2018). https://doi.org/10.1007/s00167-017-4815-0
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DOI: https://doi.org/10.1007/s00167-017-4815-0