Biomechanics Tendon Structure

In this exploration, we delve into the intricate aspects of these connective tissues.Ligaments serve as crucial connections within our soft collagenous tissues, forming links between bones. Their primary functions involve transmitting muscle forces within the skeleton, fostering joint stability, and storing and releasing elastic energy. Furthermore, ligaments play a role in providing force feedback to the nervous system through Golgi tendon organs.

While tendon and ligament have distinct functions, their mechanical properties are remarkably similar. Both are collagenous soft tissues, presenting shared challenges for repair. This similarity is pivotal in the field of orthopaedic biomechanics, given the frequent occurrence of tears and the difficulty in achieving effective repairs.

Tendons bear higher loads, tasked with transmitting muscle-generated forces to the bones. Examining their structure reveals a composition of 20% cellular material, primarily fibroblasts known as tenocytes, and 80% extracellular matrix. The matrix, comprising 50 to 70% water and 30 to 45% solids, prominently features type 1 collagen, elastin, and proteoglycans.

Collagen takes centre stage when discussing the mechanical properties of tendon and ligament. It stands out as the most abundant protein, primarily constituted of tropocollagen molecules. These molecules, forming a triple helix shape, exhibit a length of about 300 nanometres and a diameter of 1.5 nanometres. The human body hosts over 28 types of collagen, with types 1 through 4 dominating tendon and ligament structures. Collagen fibrils, with their staggered arrangement, display a positive and negative charge, facilitating cross-linking and providing an abandoned appearance. Proteoglycans intertwine with collagen fibrils, managing most of the extracellular water, resulting in a gel-like matrix. This structure allows collagen fibrils to slide past each other, a critical factor in their mechanical properties.

Within tendons and ligaments, tenocytes play a vital role in mechanotransduction. Aligned in longitudinal rows along collagen fibrils, tenocytes respond to mechanical loading by stretching and compressing. They also experience shear stress through induced fluid flow as the tissues undergo stretching and compression. With multiple extensions within the extracellular matrix, tenocytes enable communication, contributing to proprioception and force feedback loops.

Tenocytes, responsible for mechanotransduction, play a crucial role in conveying information about force transmission and inducing production and degradation of the extracellular matrix. This intricate system provides tendons and ligaments with a hierarchical structure, encompassing tropocollagen fibrils, fibres, proteoglycans, and tenocytes.

Despite their importance, tendons exhibit low vascularity, a characteristic more pronounced in ligaments. This avascular nature poses challenges for effective remodelling, a critical consideration in orthopaedic surgery where repairing tendons and promoting growth remain challenging. In addressing this challenge, platelet-rich plasma (PRP) injections have been explored as a potential therapeutic intervention. By enriching blood plasma with autologous platelets and injecting the resulting platelet layer into the tendon, researchers aim to stimulate healing processes.

In conclusion, the mechanical properties of tendon and ligament are intricately tied to their structure. The next video in this series will delve deeper into this connection, shedding light on the nuanced biomechanics of these essential connective tissues. Stay tuned for a more in-depth exploration of tendon and ligament mechanics in the upcoming segment.