A1 Journal article (refereed)
Exploration of muscle–tendon biomechanics one year after Achilles tendon rupture and the compensatory role of flexor hallucis longus (2023)

Khair, R. M., Stenroth, L., Cronin, N. J., Ponkilainen, V., Reito, A., & Finni, T. (2023). Exploration of muscle–tendon biomechanics one year after Achilles tendon rupture and the compensatory role of flexor hallucis longus. Journal of Biomechanics, 152, Article 111586. https://doi.org/10.1016/j.jbiomech.2023.111586

JYU authors or editors

Publication details

All authors or editors: Khair, Ra'ad M.; Stenroth, Lauri; Cronin, Neil J.; Ponkilainen, Ville; Reito, Aleksi; Finni, Taija

Journal or series: Journal of Biomechanics

ISSN: 0021-9290

eISSN: 1873-2380

Publication year: 2023

Publication date: 13/04/2023

Volume: 152

Article number: 111586

Publisher: Elsevier

Publication country: United States

Publication language: English

DOI: https://doi.org/10.1016/j.jbiomech.2023.111586

Publication open access: Openly available

Publication channel open access: Partially open access channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/86546


Achilles tendon (AT) rupture leads to long-term structural and functional impairments. Currently, the predictors of good recovery after rupture are poorly known. Thus, we aimed to explore the interconnections between structural, mechanical, and neuromuscular parameters and their associations with factors that could explain good recovery in patients with non-surgically treated AT rupture. A total of 35 patients with unilateral rupture (6 females) participated in this study. Muscle-tendon structural, mechanical, and neuromuscular parameters were measured 1-year after rupture. Interconnections between the inter-limb differences (Δ) were explored using partial correlations, followed by multivariable linear regression to find associations between the measured factors and the following markers that indicate good recovery: 1) tendon length, 2) tendon non-uniform displacement, and 3) flexor hallucis longus (FHL) normalized EMG amplitude difference between limbs. Δmedial gastrocnemius (MG) (β = −0.12, p = 0.007) and Δlateral gastrocnemius (β = −0.086, p = 0.030) subtendon lengths were associated with MG tendon Δstiffness. MG (β = 11.56, p = 0.003) and soleus (β = 2.18, p = 0.040) Δsubtendon lengths explained 48 % of variance in FHL EMG amplitude. Regression models for tendon length and non-uniform displacement were not significant. Smaller inter-limb differences in Achilles subtendon lengths were associated with smaller differences in the AT stiffness between limbs, and a smaller contribution of FHL muscle to the plantarflexion torque. In the injured limb, the increased contribution of FHL appears to partially counteract a smaller contribution from MG due to the elongated tendon, however the role of FHL should not be emphasized during rehabilitation to allow recovery of the TS muscles.

Keywords: tendons; calcaneal tendon; muscles; injuries and disabilities; biomechanics; ultrasonography

Free keywords: ultrasonography; flexor hallucis longus muscle; tendons; function; mechanical; muscle

Contributing organizations

Related projects

Ministry reporting: Yes

Reporting Year: 2023

Preliminary JUFO rating: 2

Last updated on 2023-03-10 at 12:01