Day: March 16, 2023

Inspired by burrs from plants, new suturing schemes show promise for surgical reattachment of tendon to bone, report researchers.

Tendon-to-bone reattachment is required in many surgical procedures, perhaps most commonly in repairing torn rotator cuff tendons in the shoulder, a condition that will affect more than 30% of the population over 60. Current suturing methods fail to distribute stress evenly, leading to failure rates as high as 94% due to ineffective attachment and re-tearing of sutures.

A team of researchers led by Guy Genin, co-director of the Center for Engineering MechanoBiology (CEMB) and professor of mechanical engineering at the McKelvey School of Engineering at Washington University in St. Louis, has developed a new approach to suturing based on the mechanics and spacing of a hitchhiker plant’s attachment system.

Their strategies show promise for balancing forces across sutures, reducing the stress on healing tendons, and potentially doubling repair strength over current suturing schemes.

The findings appear in Proceedings of the Royal Society A.

“When the late, great Barbara Pickard, a pioneer of mechanobiology who helped found the CEMB, got these burrs on her socks during a walk through the desert, she didn’t simply discard them; she latched onto this idea that nature could provide novel solutions in unexpected places,” says Genin.

Decades after Pickard’s walk, she shared her experience with burrs—similar to the hitchhiker plants that inspired hook-and-loop fastener technology—with Genin and his graduate student, Ethan D. Hoppe, lead author of the new study. For Genin and Hoppe, this was a kind of “eureka” moment.

Genin, Hoppe, and their collaborators had been studying the surgical reattachment of tendon to bone for years. They wondered, could a burr’s method of balancing forces be used in the repair of tissues?

To test this, Hoppe set out to grow some of the hitchhiker plant Pickard had encountered, Harpagonella palermi, and analyze the unique array of hooks on its fruits. Unfortunately, H. palermi is only found in a few remote patches of southwestern desert. “Your local garden store doesn’t carry these,” Hoppe notes.

After a long search, the team found collaborator Matt Guilliams, a plant systematist and curator of the Clifton Smith Herbarium at the Santa Barbara Botanic Garden, which curates native California plant species. “After Matt sent us some of the fruits he had harvested and we were able to look at them closely, we knew that we had something interesting,” Hoppe says. “The spacing and stiffness of H. palermi‘s burrs were unusual, and we set out to model how they hold on to soft materials so reliably.”

The mathematical model the team developed pointed to a unique scheme that balances forces.

“When surgeons repair something like a rotator cuff, they remove all the body’s natural connectors, which have evolved for the complex task of transitioning from hard bone to soft tendon, and put in sutures that concentrate force in a tiny area. That’s what leads to the high failure rate we see for that procedure,” Hoppe says.

“Nature has already shown us how hard materials, like the stiff hooks on a burr, can attach very effectively to soft materials like socks or a dog’s fur. We just needed to do the stress analysis to figure out how burrs compare to sutures and how this natural solution might be applied in medical practice.”

Indeed, nature’s solution to a common attachment issue may prove effective in overcoming one of the greatest challenges in orthopedic surgery. The team found that H. palermi simply and effectively balanced forces across attachment points, even when the points of connection were relatively few and the materials were substantially different. Using the mathematical model they developed to assess changes in suturing procedure based on the mechanics of hitchhiker plants, the team is now evaluating new suturing methods.

Pre-clinical testing of the new suturing methods already is underway in the laboratory of coauthor Stavros Thomopoulos, professor at Columbia University and director of Carroll Laboratories for Orthopedic Surgery.

“We are very excited to implement this concept in a real-world surgical setting,” Thomopoulos says. “Current experiments in the laboratory are evaluating how suture spacing inspired by hitchhiker plants affects rotator cuff repair strength.”

Genin and Thomopoulos anticipate that these improved techniques may be in surgical practice in the next two years.

Funding for this research came in part from the NSF Science and Technology Center for Engineering MechanoBiology and the National Institutes of Health.

Source: Washington University in St. Louis

A common and widely used chemical may be fueling the rise of Parkinson’s disease, the world’s fastest growing brain condition, researchers say.

For the past 100 years, trichloroethylene (TCE) has been used to decaffeinate coffee, degrease metal, and dry clean clothes. It contaminates the Marine Corps base Camp Lejeune, 15 toxic Superfund sites in Silicon Valley, and up to one-third of groundwater in the US.

TCE causes cancer, is linked to miscarriages and congenital heart disease, and is associated with a 500% increased risk of Parkinson’s disease.

In a hypothesis paper in the Journal of Parkinson’s Disease, researchers, including University of Rochester Medical Center neurologists Ray Dorsey, Ruth Schneider, and Karl Kieburtz, postulate that TCE may be an invisible cause of Parkinson’s. They detail the widespread use of the chemical, the evidence linking the toxicant to Parkinson’s, and profile seven individuals, including a former NBA basketball player , a Navy captain, and a late US Senator, who developed Parkinson’s disease either after likely working with the chemical or being exposed to it in the environment.

Massive TCE contamination

TCE was a widely used solvent used in a number of industrial, consumer, military, and medical applications, including to remove paint, correct typewriting mistakes, clean engines, and anesthetize patients.

Its use in the US peaked in the 1970s, when more than 600 million pounds of the chemical—or two pounds per American—were manufactured annually. Some 10 million Americans worked with the chemical or other similar industrial solvents. While domestic use has since fallen, TCE is still used for degreasing metal and spot dry cleaning in the US.

TCE contaminates countless sites across the country. Half of the most toxic Environmental Protection Agency’s (EPA) Superfund sites contain TCE. Fifteen sites are in California’s Silicon Valley where the chemicals were used to clean electronics and computer chips. TCE is found in numerous military bases, including Camp Lejeune in North Carolina. From the 1950s to the 1980s a million Marines, their families, and civilians that worked or resided at the base were exposed to drinking water levels of TCE and perchloroethylene (PCE), a close chemical cousin, that were up to 280 times above what is considered safe levels.

Soil, water, and air

The connection between TCE and Parkinson’s was first hinted at in case studies more than 50 years ago. In the intervening years, research in mice and rats has shown that TCE readily enters the brain and body tissue and at high doses damages the energy-producing parts of cells known as mitochondria. In animal studies, TCE causes selective loss of dopamine-producing nerve cells, a hallmark of Parkinson’s disease in humans.

Individuals who worked directly with TCE have an elevated risk of developing Parkinson’s. However, the authors warn that “millions more encounter the chemical unknowingly through outdoor air, contaminated groundwater, and indoor air pollution.”

The chemical can contaminate soil and groundwater leading to underground rivers, or plumes, that can extend over long distances and migrate over time. One such plume associated with an aerospace company on Long Island, New York, is over four miles long and two miles wide, and has contaminated the drinking water of thousands. Others are found everywhere from Shanghai, China to Newport Beach, California.

Beyond their risks to water, the volatile TCE can readily evaporate and enter people’s homes, schools, and workplaces, often undetected. Today, this vapor intrusion is likely exposing millions who live, learn, and work near former dry cleaning, military, and industrial sites to toxic indoor air. Vapor intrusion was first reported in the 1980s when radon was found to evaporate from soil and enter homes and increase the risk of lung cancer. Today millions of homes are tested for radon, but few are for the cancer-causing TCE.

Personal stories of Parkinson’s and TCE

The piece profiles seven individuals where TCE may have contributed to their Parkinson’s disease. While the evidence linking TCE exposure to Parkinson’s disease in these individuals is circumstantial, their stories highlight the challenges of building the case against the chemical. For these individuals, decades have often passed between exposure to TCE and the onset of Parkinson’s symptoms.

The case studies include the professional basketball player Brian Grant, who played for 12 years in the NBA and was diagnosed with Parkinson’s at age 36. Grant was likely exposed to TCE when he was three years old and his father, then a Marine, was stationed at Camp Lejeune. Grant has created a foundation to inspire and support people with the disease.

Amy Lindberg was similarly exposed to the contaminated drinking water at Camp Lejeune while serving as a young Navy captain and would go on to be diagnosed with Parkinson’s disease 30 years later.

The piece details others whose exposure was the result of living close to a contaminated site or working with the chemical, including the late US Senator Johnny Isakson, who stepped down from office after a Parkinson’s diagnosis in 2015. Fifty years earlier, he served in the Georgia Air National Guard, which used TCE to degrease airplanes.

End the use of TCE

The authors note that “for more than a century, TCE has threatened workers, polluted the air we breathe—outside and inside—and contaminated the water we drink. Global use is waxing, not waning.”

The authors propose a series of actions to address the public health threat TCE poses. They note that contaminated sites can be successfully remediated and indoor air exposure can be mitigated by vapor remediation systems similar to those used for radon. However, the US alone is home to thousands of contaminated sites and this process of cleaning and containment must be accelerated.

They argue for more research to better understand how TCE contributes to Parkinson’s and other diseases. TCE levels in groundwater, drinking water, soil, and outdoor and indoor air require closer monitoring and this information needs to be shared with those who live and work near polluted sites.

In addition, the authors call for finally ending the use of these chemicals in the US. PCE is still widely used today in dry cleaning and TCE in vapor degreasing. Two states, Minnesota and New York, have banned TCE, but the federal government has not, despite findings by the EPA as recently as 2022 that the chemicals pose “an unreasonable risk to human health.”

Additional coauthors are from Harvard University; Radboud University Medical Centre in the Netherlands; the University of California, San Francisco; the University of Alabama at Birmingham; and the University of Rochester.

Source: University of Rochester