Micromechanical properties and collagen composition of ruptured human achilles tendon

Philip Hansen; Vuokko Kovanen; Per Hölmich; Michael Krogsgaard; Patrick Hansson; Morten Dahl; Martin Hald; Per Aagaard; Michael Kjaer; S Peter Magnusson

doi:10.1177/0363546512470617

Micromechanical properties and collagen composition of ruptured human achilles tendon

Philip Hansen, Vuokko Kovanen, Per Hölmich, Michael Krogsgaard, Patrick Hansson, Morten Dahl, Martin Hald, Per Aagaard, Michael Kjaer, S Peter Magnusson

24 Citations (Scopus)

Abstract

Background: The Achilles tendon is one of the strongest tendons in the human body, and yet it frequently ruptures, which is a substantial clinical problem. However, the cause of ruptures remains elusive. Hypothesis: Ruptured human Achilles tendon displays inferior biomechanical properties and altered collagen composition compared with noninjured tendon. Study Design: Controlled laboratory study. Methods: Biopsy specimens were obtained at the rupture site and the noninjured part of the tendon (internal controls) in 17 patients with acute Achilles tendon rupture. Age- and weight-matched human cadaveric Achilles tendons (external controls) were also obtained. Tendon samples were tested micromechanically and biochemically. Results: The mean Young modulus was lower (P<.01) in ruptured (256.7 ± 100.8 MPa) and internal control tendon (262.4 ± 111.5 MPa) compared with external control tendon (512.9 ± 209. ± MPa; P<.01), whereas failure strength did not display similar differences (P = .06-.16). Collagen content, lysyl pyridinoline (LP), hydroxylysyl pyridinoline (HP), and pentosidine (PENT) did not display regional differences between ruptured and noninjured tendon. However, collagen content was less in ruptured (0.457 ± 0.093 mg/mg) and noninjured tendon (0.476 ± 0.072 mg/mg) compared with external control tendon (0.585 ± 0.044 mg/mg, P<.001). Pentosidine was similar in all tendon samples and was positively related to age in all samples (r² = 0.44-0.72, P< .05). Collagen content was positively related to failure stress but only in ruptured samples (r²= 0.36; P<.05). HP, LP, and PENT content were unrelated to failure stress and Young modulus in ruptured, noninjured, and cadaveric tendon. Conclusion: These data imply that there may be a mechanical weakening of the tendon and that a reduced collagen content may be related to the pathophysiological characteristics of Achilles tendon rupture. Clinical Relevance: Earlier studies have demonstrated that specific training regimens to treat tendon injury can improve tendon composition and mechanical properties. This study supports the notion that treatment measures should aim to increase tendon collagen content and improve micromechanical quality of the tendon matrix.

Original language	English
Journal	American Journal of Sports Medicine
Volume	41
Issue number	2
Pages (from-to)	437-43
Number of pages	7
ISSN	0363-5465
DOIs	https://doi.org/10.1177/0363546512470617
Publication status	Published - Feb 2013

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10.1177/0363546512470617

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@article{d0eeb4f228bd45c9b8fe690f66e55f6a,

title = "Micromechanical properties and collagen composition of ruptured human achilles tendon",

abstract = "Background: The Achilles tendon is one of the strongest tendons in the human body, and yet it frequently ruptures, which is a substantial clinical problem. However, the cause of ruptures remains elusive. Hypothesis: Ruptured human Achilles tendon displays inferior biomechanical properties and altered collagen composition compared with noninjured tendon. Study Design: Controlled laboratory study. Methods: Biopsy specimens were obtained at the rupture site and the noninjured part of the tendon (internal controls) in 17 patients with acute Achilles tendon rupture. Age- and weight-matched human cadaveric Achilles tendons (external controls) were also obtained. Tendon samples were tested micromechanically and biochemically. Results: The mean Young modulus was lower (P<.01) in ruptured (256.7 ± 100.8 MPa) and internal control tendon (262.4 ± 111.5 MPa) compared with external control tendon (512.9 ± 209. ± MPa; P<.01), whereas failure strength did not display similar differences (P = .06-.16). Collagen content, lysyl pyridinoline (LP), hydroxylysyl pyridinoline (HP), and pentosidine (PENT) did not display regional differences between ruptured and noninjured tendon. However, collagen content was less in ruptured (0.457 ± 0.093 mg/mg) and noninjured tendon (0.476 ± 0.072 mg/mg) compared with external control tendon (0.585 ± 0.044 mg/mg, P<.001). Pentosidine was similar in all tendon samples and was positively related to age in all samples (r2 = 0.44-0.72, P< .05). Collagen content was positively related to failure stress but only in ruptured samples (r2= 0.36; P<.05). HP, LP, and PENT content were unrelated to failure stress and Young modulus in ruptured, noninjured, and cadaveric tendon. Conclusion: These data imply that there may be a mechanical weakening of the tendon and that a reduced collagen content may be related to the pathophysiological characteristics of Achilles tendon rupture. Clinical Relevance: Earlier studies have demonstrated that specific training regimens to treat tendon injury can improve tendon composition and mechanical properties. This study supports the notion that treatment measures should aim to increase tendon collagen content and improve micromechanical quality of the tendon matrix.",

author = "Philip Hansen and Vuokko Kovanen and Per H{\"o}lmich and Michael Krogsgaard and Patrick Hansson and Morten Dahl and Martin Hald and Per Aagaard and Michael Kjaer and Magnusson, {S Peter}",

year = "2013",

month = feb,

doi = "10.1177/0363546512470617",

language = "English",

volume = "41",

pages = "437--43",

journal = "American Journal of Sports Medicine",

issn = "0363-5465",

publisher = "SAGE Publications",

number = "2",

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TY - JOUR

T1 - Micromechanical properties and collagen composition of ruptured human achilles tendon

AU - Hansen, Philip

AU - Kovanen, Vuokko

AU - Hölmich, Per

AU - Krogsgaard, Michael

AU - Hansson, Patrick

AU - Dahl, Morten

AU - Hald, Martin

AU - Aagaard, Per

AU - Kjaer, Michael

AU - Magnusson, S Peter

PY - 2013/2

Y1 - 2013/2

N2 - Background: The Achilles tendon is one of the strongest tendons in the human body, and yet it frequently ruptures, which is a substantial clinical problem. However, the cause of ruptures remains elusive. Hypothesis: Ruptured human Achilles tendon displays inferior biomechanical properties and altered collagen composition compared with noninjured tendon. Study Design: Controlled laboratory study. Methods: Biopsy specimens were obtained at the rupture site and the noninjured part of the tendon (internal controls) in 17 patients with acute Achilles tendon rupture. Age- and weight-matched human cadaveric Achilles tendons (external controls) were also obtained. Tendon samples were tested micromechanically and biochemically. Results: The mean Young modulus was lower (P<.01) in ruptured (256.7 ± 100.8 MPa) and internal control tendon (262.4 ± 111.5 MPa) compared with external control tendon (512.9 ± 209. ± MPa; P<.01), whereas failure strength did not display similar differences (P = .06-.16). Collagen content, lysyl pyridinoline (LP), hydroxylysyl pyridinoline (HP), and pentosidine (PENT) did not display regional differences between ruptured and noninjured tendon. However, collagen content was less in ruptured (0.457 ± 0.093 mg/mg) and noninjured tendon (0.476 ± 0.072 mg/mg) compared with external control tendon (0.585 ± 0.044 mg/mg, P<.001). Pentosidine was similar in all tendon samples and was positively related to age in all samples (r2 = 0.44-0.72, P< .05). Collagen content was positively related to failure stress but only in ruptured samples (r2= 0.36; P<.05). HP, LP, and PENT content were unrelated to failure stress and Young modulus in ruptured, noninjured, and cadaveric tendon. Conclusion: These data imply that there may be a mechanical weakening of the tendon and that a reduced collagen content may be related to the pathophysiological characteristics of Achilles tendon rupture. Clinical Relevance: Earlier studies have demonstrated that specific training regimens to treat tendon injury can improve tendon composition and mechanical properties. This study supports the notion that treatment measures should aim to increase tendon collagen content and improve micromechanical quality of the tendon matrix.

AB - Background: The Achilles tendon is one of the strongest tendons in the human body, and yet it frequently ruptures, which is a substantial clinical problem. However, the cause of ruptures remains elusive. Hypothesis: Ruptured human Achilles tendon displays inferior biomechanical properties and altered collagen composition compared with noninjured tendon. Study Design: Controlled laboratory study. Methods: Biopsy specimens were obtained at the rupture site and the noninjured part of the tendon (internal controls) in 17 patients with acute Achilles tendon rupture. Age- and weight-matched human cadaveric Achilles tendons (external controls) were also obtained. Tendon samples were tested micromechanically and biochemically. Results: The mean Young modulus was lower (P<.01) in ruptured (256.7 ± 100.8 MPa) and internal control tendon (262.4 ± 111.5 MPa) compared with external control tendon (512.9 ± 209. ± MPa; P<.01), whereas failure strength did not display similar differences (P = .06-.16). Collagen content, lysyl pyridinoline (LP), hydroxylysyl pyridinoline (HP), and pentosidine (PENT) did not display regional differences between ruptured and noninjured tendon. However, collagen content was less in ruptured (0.457 ± 0.093 mg/mg) and noninjured tendon (0.476 ± 0.072 mg/mg) compared with external control tendon (0.585 ± 0.044 mg/mg, P<.001). Pentosidine was similar in all tendon samples and was positively related to age in all samples (r2 = 0.44-0.72, P< .05). Collagen content was positively related to failure stress but only in ruptured samples (r2= 0.36; P<.05). HP, LP, and PENT content were unrelated to failure stress and Young modulus in ruptured, noninjured, and cadaveric tendon. Conclusion: These data imply that there may be a mechanical weakening of the tendon and that a reduced collagen content may be related to the pathophysiological characteristics of Achilles tendon rupture. Clinical Relevance: Earlier studies have demonstrated that specific training regimens to treat tendon injury can improve tendon composition and mechanical properties. This study supports the notion that treatment measures should aim to increase tendon collagen content and improve micromechanical quality of the tendon matrix.

U2 - 10.1177/0363546512470617

DO - 10.1177/0363546512470617

M3 - Journal article

C2 - 23263296

SN - 0363-5465

VL - 41

SP - 437

EP - 443

JO - American Journal of Sports Medicine

JF - American Journal of Sports Medicine

IS - 2

ER -