Rotator cuff repair often fails. To find a solution to this problem, anatomical engineers drew inspiration from nature to be able to develop new materials and designs.
A discovery by a multi-institutional team of researchers and engineers on how tendons and bones come together in the shoulder joint has developed previously unsuspected engineering strategies for welding dissimilar materials.
Guy Genin, Harold And Kathleen Faught Professor of Mechanical Engineering at the McKelvey School of Engineering at Washington University in St. Louis, And Stavros Thomopoulos, Robert E. Carroll And Jane Chace Carroll Professor of Orthopedic Surgery at Columbia University, led a team that discovered previously unknown fibrous architecture between the rotator cuff tendons and their bony attachments in the shoulder.
The results of the work have been published in the scientific journal Science Advances.
Rotator cuff: this is how the unique fibrous architecture works
Rotator cuff injuries, one of the most common tendon injuries in adults, occur when the tendons detach or rupture near the bone. To take a closer look enthesis, or to the transition material in which each of the four rotator cuff tendons attach to the bone, the team applied a new technique of computed microtomography (microCT).
The images revealed a hidden site in the enthesis of the supraspinatus tendon of the shoulder of the mouse, where tendon fibers inserted directly into the bone for approximately 30% of the well-known attachment footprint.
Through biomechanical analysis, along with numerical simulations, they found that healthy rotator cuff robustness stems from the composition, structure and location of the enthesis as the architecture of soft tissue fibrosis interacts with that of bone. It was the first time that researchers were able to see both soft and hard tissues of the rotator cuff at the same time.
“When lead author Mikhail Golman first showed us these images, we realized that much of the old image of how tendons and bones interact had to be redrawn.“, Said Genin. “The fiber system looks like fibers in a rope, and we can understand a lot where resistance comes from by understanding how these fibers sequentially break when they are close to the bone. It’s a new way of thinking about how to attach different materials “.
After the team found the hidden site, there were further discoveries as they went: “Each experiment we have done has revealed fascinating new features of the attack system“Explained Thomopoulos. “We quickly realized that the fundamental aspects of this problem had to be rethought by zero”.
“Our goal was to understand where the healthy rotator cuff gets its toughness and strength and under what conditions it breaks. We found that rotator cuff resistance varies as a function of shoulder position, helping to explain the differences in injury patterns seen in patients. “ continued the expert.
The team found that the strength of the rotator cuff comes from the fact that the fibers help build the bridge between tissue and bone. Hardness refers to how much energy is needed to break a structure, while strength refers to how much one must pull to break it.
“We found that there is actually a trade-off between strength and endurance with these fiber systems“Continued Genin. “If you reduce the overall strength by allowing some of the fibers to break, you can actually make the structure harder because it increases the amount of energy absorbed.”
The scientist claimed that their results showed that replicating the fiber structure is essential for effective and painless healing after rotator cuff repair.
The scholar said their results showed that replicating the fiber structure is essential for effective and painless healing after rotator cuff repair.:
“This research has given us a whole new look at this frequently wounded region and presented a new way of thinking about how to connect these two different materials ”.
“This is not only important for surgery, but for all kinds of engineering errors that occur when you connect a material to something with a different architecture. By blending architectural paradigms between materials and allowing the distributed failure of the joining elements, you can dramatically increase strength“, Concluded the expert.
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