Researchers have developed a “scaffold” that mimics natural tissue and could lead to more durable rotator cuff repairs, including for large injuries and cases involving bone and tissue degeneration that are often the most difficult to fix. Devised by a team at the Perelman School of Medicine at the University of Pennsylvania , the new system was detailed in Science Advances .
“Successful rotator cuff repair requires more than just simply reattaching tendon to bone because the tendon-to-bone interface has a highly organized transition from tendon to fibrocartilage to bone, and each region provides distinct signals that guide how cells behave and what type of tissue they form,” said senior author Su Chin Heo, PhD , an assistant professor of Orthopaedic Surgery and Bioengineering in the McKay Orthopaedic Research Laboratory. “The body’s cells constantly sense and respond to the physical, mechanical, and biomechanical signals in their surrounding environment. By designing our scaffold to better mimic these different microenvironments, we believe we’re able to provide the right cues in the right places for more complete and effective healing.”
Before it can be used in humans, the fix needs to go through trials in large animals. However, the team believes that, since it was designed to fit in with suturing systems used widely on current repairs, it could be taken up quickly by surgeons once proven ready.
Working in a problem joint
The rotator cuff is a joint where the arm meets the shoulder and features a variety of muscles with tendons keeping everything both moving and in place. Roughly 250,000 people each year in the United States alone require surgery on the joint. While athletes who rely on constant throwing motions—such as baseball players and football quarterbacks—can be susceptible, rotator cuff injuries are extremely common among older adults, with about 40% of people 60 or older experiencing injuries to the joint .
Average rotator cuff repair is conducted via minimally invasive arthroscopic procedures, ending with the reattachment of damaged tendons via “suture anchors” (a system that uses anchoring screws and thread) in the arm bone. However, many of these repairs fail to heal properly, in part because they do not recreate the natural transition from tendon to cartilage-like tissue to bone that helps to guide healing.
So, Heo and his team set out to design a repair system that does more than simply hold tendon and bone together—one that more closely recreates the different tissue environments found naturally to help guide healing.
Creating a scaffold for the shoulder joint
The team created a scaffold with different regions designed to recreate the natural transition from tendon to cartilage-like tissue to bone. The tendon and cartilage-like regions used nanofibers derived from cow Achilles tendons combined with hyaluronic acid, while the bone region used a citrate-based porous material designed to support bone integration. Importantly, the scaffold was designed to integrate with existing suture anchor systems already used in rotator cuff repair.
When the researchers tested their system in cells in the lab, they noted that its different regions guided stem cells toward forming tendon- and cartilage-like tissues. In addition, on animal models of rotator cuff injuries, they noted that the scaffold also promoted more organized formations of tendons, cartilage-like tissue, and bone at the repair site, more closely resembling the body’s natural tendon-to-bone connection than repairs without the scaffold.
Helping patients with no alternatives
The large population of older patients who suffer these injuries often has complicating factors that make a rotator cuff repair unlikely to succeed or even not an option. That can include past repairs failing, poor quality of their tendons, and the general slow-down in healing capacity that comes with age.
“There are wide populations of people whose repair chances are limited,” said first author Zizhao (Molly) Li, PhD , in the McKay Orthopaedic Research Laboratory. “Many patients with large tears, poor tissue quality, or failed previous repairs have limited treatment options. By recreating the biology of the native tendon-to-bone interface, we hope to improve the quality and durability of healing for these challenging cases.”
This work was supported in part by grants from the National Institutes of Health (K01 AR07787, R21 R077700, P30 AR069619, and R01 HL163168) and the National Science Foundation (CMMI 1548571).
Science Advances
Experimental study
Animals