A device inspired by the Python tooth doubles the strength of rotator cuff repairs

When most people think of pythons, they imagine a huge snake choking and swallowing its prey whole. But did you know that pythons initially hold onto their prey using sharp, backward-curved teeth? Medical scientists have long known that these teeth are ideal for gripping soft tissue rather than cutting it, but no one has yet been able to apply this concept to surgical practice. Over the years, imitating these teeth for use in surgery has been a common topic of discussion in Dr.’s lab. Stavros Thomopoulos, professor of orthopedics and biomedical engineering at Columbia University.

Biomimicry the key to new research

As a leading researcher in the development and regeneration of the tendon-to-bone attachment, Thomopoulos has a particular interest in advancing tendon-to-bone repair necessary for rotator cuff repair and anterior cruciate ligament reconstruction. In an article published today by progress of science, His team reports that they have developed a python-tooth-inspired device to complement the current method used to repair rotator cuff sutures and have found that it almost doubles the strength of the repair.

“As we age, more than half of us will experience rotator cuff damage leading to shoulder pain and limited mobility,” said Thomopoulos, who as Robert E. Carroll has joint appointments at Columbia Engineering and Vagelos College of Physicians and Surgeons at Columbia and the Jane Chace Carroll Professor biomechanics (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, based on python tooth design, helps reattach tendons to bone more safely. The device not only increases the strength of the repair, but can also be adapted to the patient. We are really excited about the potential of our device to improve the treatment of rotator cuff injuries.

Rotator cuff injuries

Rotator cuff tears are the most common tendon injury, affecting more than 17 million people in the United States each year. The incidence of injuries increases with age: over 40% of the population over the age of 65 experience rotator cuff tears.

Because rotator cuff tears usually occur at the site of the tendon’s attachment to the bone, rotator cuff repair aims to anatomically restore the tendon’s attachment. Surgical repair is the primary method of restoring shoulder function. More than 600,000 procedures are performed in the United States each year at a cost of $3 billion.

However, successful reattachment of the tendon to the bone remains a major clinical challenge. High failure rates occur after surgery, and rates increase with patient age and tear severity. These rates range from 20% in younger patients with small 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 two or four points of attachment, where forces are concentrated.

Although there have been advances in rotator cuff repair techniques over the past 20 years, the basic approach of suturing two tissues together has remained largely unchanged, still relying on tension-bearing sutures at high-stress attachment points. After surgery to reattach the tendon to the bone, the sutures can tear the tendons at these high stress points, a phenomenon known as “suture pulling” or “cheesewiring,” which leads to the repair site opening or tearing.

“We set out to see if we could develop a device that mimics the shape of a python’s teeth, that would effectively grip soft tissue without tearing 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 biomedical engineering graduate student in Thomopoulos’ lab. .

Device

The team’s initial idea was to copy the shape of a python’s teeth, but they went much further using simulations, 3D printing and Live cadaver experiments to investigate the relationship between tooth shape and the mechanics of grasping and cutting. Kurtalij produced a series of tooth designs, optimized individual teeth, tooth arrangements, and finally a set of teeth adapted to the rotator cuff. The end result was a biomimetic device made of biocompatible resin—an arrangement of teeth on a curved base—that could grasp rather than cut the tendon. The teeth are relatively small—3 mm tall for a human rotator cuff, or about half the length of a standard brace—so they don’t penetrate the tendon. The base can be customized using 3D printing to fit the patient’s specific curvature of the humeral head at the insertion of the supraspinatus tendon (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 a device and increase the strength of the repair.”

Iden Kurtaliaj, lead author of the study

Team

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

“Thanks to our lab’s close collaboration with orthopedic surgeons, we were particularly fortunate to have the assistance of Dr. Levine and other Columbia surgeons throughout the device design process,” Thomopoulos said.

Next steps

Scientists are currently 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 utility. They are also preparing for a pre-application meeting with the FDA to help bring the device to market.