New device inspired by python teeth may reduce risk of rotator cuff re-tear

When most people think of pythons, they visualize the enormous snake constricting and swallowing its victims whole. But did you know that pythons initially hold their prey with their sharp, backward-curving teeth?

Medical researchers have long been aware that these teeth are perfect for gripping soft tissue rather than cutting through it, but no one has yet been able to bring this concept into surgical practice. Over the years, replicating these teeth for use in surgery has been a frequent topic of discussion in Dr. Stavros Thomopoulos, professor of orthopedics and biomedical engineering at Columbia University.

Biomimicry key to new research

Thomopoulos is a leading researcher who focuses on the development and regeneration of the attachment of tendons to bones. He is particularly interested in improving tendon-to-bone repair, which is necessary for rotator cuff repair and anterior cruciate ligament reconstruction.

In an article published by Science progress, his team reports that they have developed a python teeth-inspired device to complement current rotator cuff suture repair, and found that it nearly doubles repair strength.

“As we age, more than half of us will experience a rotator cuff tear leading to shoulder pain and decreased mobility,” says Thomopoulos, who holds joint appointments at Columbia Engineering and Columbia’s Vagelos College of Physicians and Surgeons as Robert E. Carroll. and Jane Chace Carroll Professor of Biomechanics (in orthopedic surgery and biomedical engineering).

“The best medical intervention is rotator cuff surgery, but a remarkably high percentage of these repairs will fail within a few months. Our biomimetic approach, based on the design of python teeth, helps to more firmly attach tendons to bone. It device not only increases the strength of the repair, but is also customizable to the patient. We are very excited about the potential of our device to improve the care of rotator cuff injuries.”

Rotator cuff injuries

Of the most common tendon injuries, rotator cuff tears, affect more than 17 million people in the United States each year. The incidence of injury increases with age: more than 40% of the population over 65 years of age experiences a rotator cuff tear.

Because tears in the rotator cuff usually occur where the tendon inserts into the bone, rotator cuff repair is aimed at anatomically restoring the tendon attachment. Surgical repair is the main treatment for restoring shoulder function; In the United States, more than 600,000 procedures are performed annually at a cost of $3 billion.

However, successful tendon-to-bone reattachment remains a significant clinical challenge. High failure rates occur following surgery, with rates increasing with patient age and severity of tear. These rates range from 20% in younger patients with small tears to as high as 94% in older patients with massive tears. The most common failure of rotator cuff repairs is tearing of sutures through the tendon at the two or four attachment points where forces are concentrated.

Although there have been advances in rotator cuff repair techniques over the past 20 years, the fundamental approach of suturing two tissues together has remained largely unchanged. Sutures that transfer tension to high-tension grasping points are still used.

Following tendon-to-bone reattachment surgery, the sutures at these high-tension points can tear through the tendons, a phenomenon known as “suture pull-through” or “cheesewire,” resulting in holes or tears at the repair site.

“We decided to see if we could develop a device that mimics the shape of python teeth, that effectively grips soft tissues without tearing, and helps reduce the risk of the tendon tearing again after rotator cuff repair,” says Iden Kurtaliaj, head of research. lead author and former biomedical engineer Ph.D. student in Thomopoulos’ laboratory.

The device

The team’s original idea was to copy the shape of python teeth, but they went much further, using simulations, 3D printing, and ex vivo experiments on cadavers to investigate the relationship between tooth shape and grasping versus cutting mechanisms.

Kurtaliaj produced a series of tooth designs, optimizing individual teeth, sets of teeth, and ultimately a rotator cuff-specific set of teeth. The end result was a biomimetic device made of a biocompatible resin—a set of teeth atop a curved base—capable of gripping, not cutting, tendons.

The teeth are relatively small (3mm high for a human rotator cuff, about half the length of a standard staple) so they do not protrude through the tendon. The base can be adjusted via 3D printing to match the patient-specific curvature of the humeral head at the attachment site of the supraspinatus tendon (the most commonly torn tendon of the rotator cuff).

“We designed it specifically so that surgeons don’t have to abandon their current approach. They can simply add the device and increase the strength of their repair,” Kurtaliaj said.

Kurtaliaj led the research as a Ph.D. student under the supervision of Drs. Stavros Thomopoulos and Guy Genin, the Harold and Kathleen Faught Professor of Mechanical Engineering at Washington University in St. Louis, with input into Dr.’s clinical implementation. William Levine, chairman of the Department of Orthopedic Surgery at Columbia University’s College of Physicians and Surgeons.

“Thanks to our laboratory’s close collaboration with orthopedic surgeons, we were especially pleased to have input from Dr. Levine and other surgeons at Columbia throughout the device design and development process,” said Thomopoulos.

The researchers are now working to develop a bioabsorbable version of the device that would break down as the rotator cuff heals back to the bone, further improving its clinical applicability. They are also preparing for a pre-submission meeting with the FDA to ease the transition of their device to the market.