The shape of an individual Achilles tendon can help indicate that patients are more likely to be injured

Individual differences in the shape and structure of the Achilles tendon may affect our susceptibility to injuries later in life, says a study published today in eLife.

The findings suggest that the study of individual Achilles tendon shape (or ‘morphology’) may help identify patients at risk of injury and devise new approaches that may be personal for the treatment and prevention of Achilles tendinopathy and similar conditions.

The Achilles tendon is the tendon that connects the calf muscles to the heel bone. It is fundamental to our mobility and athleticism. Its unique structure, which combines three smaller sub-tendons, increases the efficiency of our movement by allowing individual control from connected muscles.

For this control to occur, the sub-tendons must work together and allow a certain degree of slip between them. But the ability of the sub-tendons to slip decreases with age, possibly accounting for a greater frequency of injury that is sometimes seen later in life.

Each sub-tendon should be viewed as a separate unit of work within the Achilles tendon as a whole to fully understand how force is circulated within the tendon. But the conventional medical imaging methods do not allow us to accurately visualize the boundaries of the sub-tendons in living humans. This means that the relationship between sub-tendon morphology, mechanical behavior and risk of injury is not yet clear.. “

Nai-Hao Yin, Principal study author and PhD student, Institute of Orthopedics and Musculoskeletal Science, University College London

To help address this gap, Yin and colleagues began by examining five human Achilles tendon samples, from two males and three females. They performed mechanical tests on the sub-tendons of the samples to compare their different mechanical properties. Next, they recorded the morphology of the sub-tendons of three additional samples, from two males, ages 54 and 55 years, and one female, ages 14, selected to represent a range of individual differences in morphology. tendonology.

“Our tests showed specific mechanical properties in the sub-tendons according to their mechanical applications,” Yin says. “We identified a significant difference in the direction of the sub-tendons from different individuals.”

The team then created computer models using the data obtained from their experiments. They used a simulation technique to study how different sliding structures affect sub-tendon movement and force circulation within the different models. They were of particular interest in the muscle-tendon soleus junction, as this area is widely used to measure tendon mechanical properties.

Next, they investigated whether the results of their modeling tests would reveal an age-related decline in sub-tendon slippage in humans. They employed two groups of study participants: a group of seven older participants, aged 52–67 years, and a younger group of nine participants, ages 20–29 years.

They applied electrical stimulation to the participants’ calf muscles and recorded the changes occurring in the crosshairs. The older group of participants showed less slip compared to the younger group, showing the same trend as the model result when the team examined the sub-tendon soleus alone.

“Our work shows that the mechanical behavior of the Achilles tendon is complex and influenced by a variety of factors, including sub-tendon mechanical properties and morphology, and age-related changes in their ability to slip, “concludes lead author Helen Birch, Professor of Tissue Skeletal Dynamics at the UCL Institute of Orthopedics and Musculoskeletal Science.” later in life. We hope that our findings will pave the way for further research on how these factors can affect sub-tendons differently among individuals, and ultimately continue. to new injury treatment and prevention strategies. “