New device inspired by python’s teeth may reduce risk of rotator cuff tear

Most people, when they think of pythons, visualize the large snake that constricts and swallows its victims whole. But did you know that pythons first hold their prey with their sharp, backward-curved 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 apply this concept to surgical practice. Over the years, the imitation of these teeth for use in surgery has been a frequent topic of discussion in the laboratory of Dr. Stavros Thomopoulos, a professor of orthopedics and biomedical engineering at Columbia University.

Biomimicry key to new study

A leading researcher focused on the development and regeneration of the tendon-to-bone connection, Thomopoulos is particularly interested in advancing tendon-to-bone repair, necessary for rotator cuff repair and anterior cruciate ligament reconstruction.

In a paper published by Advances in science, His team reports that they developed a device inspired by python teeth as an adjunct to current rotator cuff suture repair and found that it nearly doubled the strength of the repair.

“As we get older, more than half of us will experience a rotator cuff tear that leads to shoulder pain and decreased mobility,” said Thomopoulos, who holds joint appointments at Columbia Engineering and the Vagelos College of Physicians and Surgeons of Columbia 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 an extremely high percentage of these repairs will fail within just a few months. Our biomimetic approach behind the design of python teeth helps to reattach tendons to bone more securely. The device not only does it increase the power of repair, but it can also be customized for the patient.

Rotator cuff injuries

Among 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 the age of 65 experience a rotator cuff tear.

Because rotator cuff tears usually occur at the tendon-to-bone insertion site, rotator cuff repair aims to anatomically restore the tendon attachment. Surgical repair is the primary treatment for restoring shoulder function, with more than 600,000 procedures performed each year in the United States at a cost of $3 billion.

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

While there have been advances in rotator cuff repair techniques over the past 20 years, the basic approach of suturing the two tissues together has remained largely unchanged, still relying on sutures that transfer tension to high-stress attachment points.

After tendon-to-bone reattachment surgery, sutures can tear the tendons at these high stress points, a phenomenon known as “suture pulling” or “cheese binding,” leading to tears or tears at the repair site.

“We set out to see if we could develop a device that mimics the shape of python teeth that would effectively grip soft tissue without tearing and help reduce the risk of tendon re-rupture after rotator cuff repair.” said Iden Kurtaliaj, the study’s researcher. lead author and a former biomedical engineering Ph.D. student in Thomopoulos’ lab.

DEVICE

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

Kurtaliaj produced a series of tooth patterns, optimized individual teeth, groups of teeth and finally a set of teeth specific to the rotary cuff. The end result was a biomimetic device, made from a biocompatible resin—a set of teeth on a curved base—capable of gripping, not cutting, the tendon.

The teeth are relatively small—3mm high for a human rotator cuff, about half the length of a standard clip—so they don’t go through the tendon. The base can be customized via 3D printing to fit the patient-specific curvature of the humeral head at the supraspinatus tendon (the most commonly torn rotator cuff tendon) attachment site.

“We designed it specifically so surgeons don’t have to abandon their current approach — they can just add the device and increase the power of their repair,” Kurtaliaj noted.

Kurtaliaj led the research as a Ph.D. student under the mentorship of Dr. Stavros Thomopoulos and Guy Genin, Harold and Kathleen Faught Professor of Mechanical Engineering at Washington University in St. Louis.

“Because of our lab’s close collaboration with orthopedic surgeons, we were especially fortunate to receive input from Dr. Levine, along with other surgeons at Columbia, throughout the device design development process,” said Thomopoulos. .

Researchers are now working to develop a bioabsorbable version of the device that would degrade as the rotator cuff heals back into the bone, further increasing its clinical applicability. They are also preparing for a pre-submission meeting with the FDA to facilitate the transition of their device to market.