Novel medical approaches feature plastics

Several new medical devices make interesting use of plastics.

DSM Dyneema Purity ultra-high-molecular-weight-polyethylene fiber plays a key role in SpineWorks' Universal Screw Persuader (USP) System, which is used in spinal surgery.

SpineWorks believes the USP System will be compatible with almost all pedicle screw systems currently marketed for complex, such as coliosis, and simple procedures, such as those  related to degenerative issues and trauma.

Polysulfone is used in a shunt assembly. Photo: Solvay Specialty Polymers

Pedicle screws are sometimes used in spinal fusion surgery to provide a way to grip a spinal segment. The screws act as anchor points that can be connected with a rod.

The Dyneema Purity fiber in the cable is used to encircle and anchor to the bottom of a pedicle screw. The lasso is then attached to a proprietarily designed instrument that brings the rod to the screws. The lasso is then cut and removed from the surgical site for disposal.  

"We chose Dyneema Purity fiber due to its prolonged track record of use in the medical industry and proven strength, abrasion resistance and biocompatibility," says Doug Neary, president, SpineWorks (Huntington Beach, CA).

In another development, polysulfone will be used in an implantable brain shunt, one of the fastest-growing applications in the medical market. The new shunt from Integra LifeSciences Corp. (Plainsboro, NJ) is part of a multi-piece assembly that is implanted during brain surgery for hydrocephalus fluid management. They are injection molded by Integra LifeSciences.

The PSU comes from Solvay Specialty Polymers (Alpharetta, GA).  Solvay says that its Eviva PSU is a transparent resin that offers practical toughness. The material maintains its dimensional tolerance right out of the mold and requires no machining.

Simpliciity trial begins

And in what some feel may be the biggest medical device story of the next year, Medtronic announced the

Nerve modulation near kidneys may save many from persistent hypertension. Photo: Medtronic

start of a U.S. clinical trial of the Symplicity Renal Denervation System for treatment-resistant hypertension. The first patient is at the Prairie Heart Institute at St. John's Hospital in Springfield, IL.

Hypertension that persists despite use of  three or more medications puts approximately 120 million people worldwide at risk of premature death from kidney disease, stroke, heart attack or heart failure.

Renal denervation is described as a minimally invasive, catheter-based procedure that modulates the output of nerves that line the walls of the arteries leading to the kidneys. The targeted nerves are part of the sympathetic nervous system, which Medtronic scientists say has a central role in blood pressure regulation.

The study will enroll approximately 530 treatment-resistant hypertension patients across 60 U.S. medical centers.

"Renal denervation has the potential to extend the lives of millions of people who suffer from treatment-resistant hypertension," says Krishna Rocha-Singh, medical director of the Prairie Vascular Institute and the Prairie Education and Research Cooperative. "Based on the results of prior clinical studies and contemporary clinical practice, this interventional technique could be one of the most significant advances in our approach to addressing this insidious disease to be developed in decades."

Company officials would not disclose to the types of plastics used in the Simplicity system.


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