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Most people, when they think of pythons, visualize the huge snake that coils and swallows victims whole. But did you know that pythons initially hold their prey with their sharp, backward-curved 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 concept 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 Tomopoulos, professor of orthopedics and biomedical engineering at Columbia University.

Biomimicry is key to new research

A leading researcher focused on tendon-to-bone attachment development and regeneration, Tomopoulos is particularly interested in the advancement of tendon-to-bone repair required for rotator cuff repair and anterior cruciate ligament reconstruction.

In an article published by Scientific progress, his team reports that they developed a device inspired by a python’s tooth as an adjunct to current rotator cuff suture repair and found that it nearly doubled the strength of the repair.

“As we age, more than half of us will develop a rotator cuff tear, leading to shoulder pain and reduced mobility,” said Tomopoulos, who holds joint appointments at Columbia Engineering and Columbia’s Vagelos College of Physicians and Surgeons as the Robert E. Carroll and Jane Chase 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 after just a few months. Our biomimetic approach, following the design of python teeth, helps attach tendons to bone more securely. The device not only increases the strength of the repair, but 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 65 years suffers a rotator cuff tear.

Because rotator cuff tears usually occur at the site of tendon-to-bone insertion, rotator cuff repair is aimed at anatomic restoration of the tendon attachment. Surgical repair 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 reattachment of tendon to bone 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 mild tears to a staggering 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.

Although there have been advances in rotator cuff repair techniques over the past 20 years, the basic bi-tissue suturing approach remains largely unchanged, still relying on tension-transfer sutures at high-stress catch points.

After surgery to reattach a tendon to bone, sutures can tear the tendons at these points of high stress, a phenomenon known as “suture pulling” or “cheeseing,” resulting in a tear or tear at the repair site.

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

The 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 investigate the relationship between the shape of the teeth and the mechanics of grasping versus cutting.

Kurtaliaj produced a set of tooth designs, optimized individual teeth, arrays of teeth and finally a rotator cuff specific set of teeth. The end result was a biomimetic device made of biocompatible resin—a set of teeth on a curved base—capable of grasping rather than cutting a tendon.

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

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

Kurtaliaj led the research as a Ph.D. student under the mentorship of Dr. Stavros Tomopoulos and Guy Genin, the Harold and Kathleen Fauth Professor of Mechanical Engineering at Washington University in St. Louis, with clinical application input from Dr. William Levin, chairman of the Department of Orthopedic Surgery at Columbia University’s College of Physicians and Surgeons.

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

Researchers are now working to develop a bioabsorbable version of the device that will degrade as the rotator cuff heals back to the bone, further improving its clinical applicability. They are also preparing for a preliminary meeting with the FDA to ease the transition of their device to market.