A Novel Measurement of Altered Achilles Subtendon Load Sharing 6-12 Months Following Rupture

Area of Science:

• Biomedical Engineering
• Musculoskeletal Research
• Rehabilitation Science

Background:

• Achilles tendon ruptures lead to lasting functional deficits.
• Healthy Achilles tendons feature three semi-independent subtendons.
• Post-rupture, reduced subtendon sliding and increased load sharing occur, potentially due to adhesions.

Purpose of the Study:

• To quantify subtendon load sharing 6-12 months after Achilles tendon rupture.
• To assess changes in subtendon independence during muscle activation in recovering patients.
• To identify potential biomarkers for tendon health post-injury.

Main Methods:

• Utilized transverse plane ultrasound imaging and neuromuscular electrical stimulation.
• Applied Kanade-Lucas-Tomasi point tracking to analyze subtendon behavior.
• Developed a surrogate measure for subtendon load sharing based on displacement trajectory angles.

Main Results:

• Injured Achilles tendons showed significantly increased subtendon load sharing compared to the uninjured contralateral side.
• This effect was observed during stimulations of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles.
• Injured tendons exhibited up to a 44% decrease in subtendon independence.

Conclusions:

• Increased subtendon load sharing is a significant indicator of Achilles tendon injury.
• This phenomenon suggests reduced subtendon independence post-rupture.
• Findings propose a novel biomarker for tendon health and highlight muscle-dependent functional changes.