New device inspired by python teeth could reduce risk of rotator cuff tears

Most people, when they think of pythons, visualize the enormous snake contracting and swallowing its victims whole. But did you know that pythons first latch on to their prey with their sharp, backward-curved teeth?

Medical researchers have long known that these teeth are ideal for grasping soft tissue rather than cutting it, but no one has yet been able to put the concept into surgical practice. Over the years, mimicking these teeth for surgical purposes has been a frequent topic of discussion in the lab of Dr. Stavros Thomopoulos, a professor of orthopedics and biomedical engineering at Columbia University.

Biomimicry is key to new study

A leading researcher focused on the development and regeneration of the tendon-bone attachment, Thomopoulos has a particular interest in the advancement of tendon-bone repair, which is necessary for rotator cuff repair and ligament reconstruction anterior cruciate.

In an article published by Scientists progress, his team reports developing a python tooth-inspired device to complement current rotator cuff suture repair, and found that it nearly doubled repair strength.

“As we age, more than half of us will suffer a rotator cuff tear that causes shoulder pain and decreased mobility,” said Thomopoulos, who holds joint appointments at Columbia Engineering and Columbia’s Vagelos College of Physicians and Surgeons as the 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 fail within months. Our biomimetic approach inspired by python teeth allows for more secure reattachment of tendons to bone. The device not only increases the strength of the repair, but can also be customized to the patient. We are very excited about the potential of our device to improve the care of rotator cuff injuries.”

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 injuries increases with age: more than 40% of the population over 65 suffers from a torn rotator cuff.

Because rotator cuff tears typically occur at the site where the tendon insertion into the bone, rotator cuff repair aims to anatomically restore the tendon’s 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. Failure rates are high after surgery, increasing with patient age and tear severity. These rates range from 20% in younger patients with minor tears to 94% in older patients with massive tears. The most common failure of rotator cuff repairs is tendon tearing through the suture at the two or four grasping points where forces are concentrated.

Although advances have been made in rotator cuff repair techniques over the past 20 years, the fundamental approach of sewing two tissues together has remained largely unchanged, still relying on sutures transferring tension to high-stress grasping points.

After tendon-to-bone reattachment surgery, sutures can tear tendons at these high-stress points, a phenomenon known as “suture pull” or “cheesewiring,” leading to gapping or rupture at the repair site.

“We decided to see if we could develop a device that mimicked the shape of python teeth, which would effectively grip soft tissue without tearing it and help reduce the risk of re-tearing the tendon after rotator cuff repair.” , said Iden Kurtaliaj, lead author of the study and a former doctoral student in biomedical engineering in Thomopoulos’ lab.

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 explore the relationship between tooth shape and gripping and cutting mechanics.

Kurtaliaj made a range of tooth models, optimizing individual teeth, rows of teeth, and finally a row of teeth specific to the rotator cuff. The end result was a biomimetic device, made from a biocompatible resin—a row of teeth on a curved base—that can grip, not cut, the tendon.

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

“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 noted.

Kurtaliaj led the research as a doctoral student under the mentorship of Drs. Stavros Thomopoulos and Guy Genin, the Harold and Kathleen Faught Professor of Mechanical Engineering at Washington University in St. Louis, with input for implementation clinic of Dr. William Levine, Chairman of the Department of Orthopedic Surgery at Columbia University College of Physicians and Surgeons.

“Thanks to our lab’s close collaboration with orthopedic surgeons, we were fortunate to have input from Dr. Levine, as well as other Columbia surgeons, throughout the device design development process,” Thomopoulos said.

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