The Python tooth-inspired device doubles the power of rotator cuff repairs

Most people, when they think of pythons, envision the huge snake writhing and swallowing victims whole. But did you know that pythons initially hold their prey with their sharp, backward-curving teeth? Medical researchers have long known that these teeth are ideal for gripping soft tissue rather than cutting through it, but no one has yet been able to apply this idea to surgical practice. Over the years, mimicking these teeth for use in surgery has been a frequent topic of discussion in the laboratory of Dr. Stavros Thomopoulos, professor of orthopedic and biomedical engineering at Columbia University.

Biomimetic key to new study

A leading researcher focused on tendon-to-bone attachment development and regeneration, Thomopoulos is particularly interested in promoting tendon-to-bone repair, essential for rotator cuff repair and anterior cruciate ligament repair. In a paper published today by science progress, 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 repair force.

“As we get older, more than half of us will experience a rotator cuff tear that will lead to shoulder pain and reduced mobility,” said Thomopoulos, who holds joint appointments at Columbia Engineering and its Vagelos College of Physicians and Surgeons. Columbia 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 an extremely high percentage of these repairs will fail within a few months. Our biomimetic approach after designing the python teeth helps to more securely reattach the tendons to the bones. The device not only increases the strength of the repair, but can also be customized to the patient.We are really 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 frequency of injury increases with age: more than 40% of the population over 65 years of age develops a rotator cuff tear.

Because rotator cuff tears usually occur at the point of insertion of the tendon into bone, rotator cuff repair aims to anatomicly restore the tendon attachment. Surgical reconstruction is the primary treatment for restoring shoulder function, with more than 600,000 procedures performed annually 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 after surgery, 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 sutures that tear the tendon at the two or four capture points where forces are concentrated.

While advances have been made in rotator cuff repair techniques over the past 20 years, the fundamental approach of suturing two tissues together has remained largely unchanged, continuing to rely on sutures that transfer tension to high-pressure catch 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 stringing,” leading to a gap or tear at the repair site.

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

The device

The team’s initial idea was to replicate the shape of the python’s teeth, but they went much further, using simulations, 3D printing and ex vivo cadaver experiments to investigate the relationship between tooth shape and mechanical grasping versus cutting; Kurtaliaj built a series of tooth designs, optimized individual teeth, rows of teeth, and finally a row of teeth specifically for the rotary petal. The end result was a biomimetic device, made of biocompatible resin — a series of teeth atop a curved base — capable of gripping rather than cutting the tendon. The teeth are relatively small — 3 millimeters high for a human rotator cuff, about half the length of a standard clip — so they don’t pierce through the tendon. The base can be customized via 3D printing to match the curvature of the humeral head at the supraspinatus tendon (the most commonly torn rotator cuff tendon) attachment point for the patient.

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

Iden Kurtaliaj, lead author of the study

The team

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

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

Next steps

The researchers are now working to develop a bioresorbable version of the device that would degrade as the rotator cuff heals back into bone, further enhancing its clinical application. They are also preparing for a pre-submission meeting with the FDA to ease their device’s transition to market.