The microstructure and micromechanics of the tendon-bone insertion

Revealing the hidden strength of Achilles-heel connection

23 August 2017

Advanced imaging has provided insight into how the Achilles tendon remains connected to the heel bone despite regular mechanical stress and deformation.

A team led by researchers at the Technical University of Munich combined electron microscopy, confocal microscopy, and high-resolution microcomputed tomography to examine the connection between the Achilles tendon and the heel bone in pigs. Analysis revealed that the tendon unravels into thinner ‘interface fibres’ that fan out and connect to the bone. This arrangement ensures that different subsets of fibres bear the load associated with force from different angles.

The composition of tissues also varies along the connection. While the tendon consists of aligned strands of fibrous type I collagen, the interface fibres are made of type II collagen, a key component of flexible cartilage. The interface region also has a higher concentration of cartilage-related proteins, keeping it supple.

In addition to explaining the durability of this connection, these findings may help guide biomimetic strategies for engineering connections between hard and soft materials.

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References

1. Nature Materials 16, 664-669 (2017). doi: 10.1038/nmat4863