Table of Contents

bovine - from cattle

cadaver - dead body, corpse

cerebellar tonsils - portion of the cerebellum located at the bottom, so named because of their shape

cerebellum - part of the brain located at the bottom of the skull, near the opening to the spinal area; important for muscle control, movement, and balance

cerebrospinal fluid (CSF) - clear liquid in the brain and spinal cord, acts as a shock absorber

Chiari malformation - condition where the cerebellar tonsils are displaced out of the skull area into the spinal area, causing compression of brain tissue and disruption of CSF flow

collagen - fibrous material that holds together skin, tendon, and bone; referred to as the glue that holds tissue together

decompression surgery - common term for any of several variations of a surgical procedure to alleviate a Chiari malformation

dura - thick outer layer covering the brain and spinal cord

duraplasty - surgical procedure where a patch - or graft -  is sewn into the dura

herniorraphy - surgical hernia repair

organism - a living thing

pathogen - an organism that causes disease

posterior fossa - depression on the inside of the back of the skull, near the base, where the cerebellum is normally situated

scaffold - structure which provides support during construction

sterilize - procedure to destroy all life (germs, microbes, etc.) on an object

submucosa - connective tissue beneath the mucous membrane

syringomyelia - neurological condition where a fluid filled cyst forms in the spinal cord

In addition to thinking about what is being removed from their body, namely bone, a Chiari patient must also think about what is being put into their body.  Many patients undergo a duraplasty, a procedure where a patch is sewn - or grafted - into the dura covering their brain.  While this creates more space, the choice of dural graft material is one of the most controversial aspects of Chiari surgery.

Doctors and researchers have been looking for an ideal dural substitute for a long time and many types of material have been tried.  The dural graft must be flexible, easily sewn to prevent leaks, and not rejected by a person's body.  Some of the more common materials used in Chiari surgeries include material taken from cows, cadavers (I shudder when I think about having a piece of someone else in my skull), and synthetic materials. 

Despite the many options, to date consensus has not been reached on which material is the best to use.  And with the growing concern of disease transmission, and the complications that are associated with the graft, the decision of which type of graft to use has become even more important.

COOK Inc. (see Community News) has announced a new product, Durasis, which promises to shake up the status quo.  While not yet commercially available (it will be available soon), the material received FDA approval and COOK agreed to give us a sneak peak into what this exciting product is all about.

To learn more about their new dural graft product, we put Andy Cron, Vice President of Cook Surgical  Into The Spotlight...

What is Durasis?
C: Durasis is an SIS (small intestinal submucosa) product developed to be used in the surgical repair and replacement of the dura mater that surrounds the brain and spinal cord.

Can you describe – in layman’s terms – the underlying technology?
C:  Durasis utilizes Cook’s innovative Small Intestinal Submucosa (SIS) technology, a collagen biomatrix that supports regrowth of host tissue. SIS is a natural biomaterial harvested from pig small intestine and developed into strong, sterile, pliable sheets that provide a rich environment for cell attachment and tissue growth.

In your literature, what do you mean by “takes on the cellular characteristics of dural tissue”?
C:  Durasis takes on the cellular characteristics of surrounding dural tissue while it serves as a scaffold on which human tissue grows. As the biomaterial is replaced with cells, the scaffold is no longer needed and it is absorbed by the body. The result is a tissue that looks and functions very much like the tissue it replaced.

What are the benefits of using Durasis?
C:  Durasis is a nearly ideal dural substitute, it is easy to handle and suture, has exceptional strength, is durable, and has the advantage of remodeling into native tissue.

How many people was Durasis tried in before FDA approval?
C:  A total of 59 patients in our study received DURASIS, and there has been a report describing outcome in 51 of these patients.

Is the product approved for specific applications, or is it up to the surgeon to decide when to use it?
C:  Durasis is approved for use as a dural substitute for repairing dura mater. It was specifically designed to repair this unique tissue that covers the brain and spinal cord.

What was the complication rate (directly related to the patch, CSF leaks for example)?
C:  The results obtained in this multicenter study are encouraging. The incidence of CSF leak was low (2%), considering the fact that 78% of the grafts were used in the posterior fossa or spine. There was no evidence of rejection or inflammatory reaction. In the wound infections reported, there was no evidence of Durasis being affected. Similar results were seen in use of SIS for herniorraphy where it was shown to be well-suited for use in contaminated fields. Handling characteristics were also excellent. Durasis is a promising new dural graft substitute.

In Chiari decompressions, it has been shown that sometimes the dual patch becomes thickened, stiff, and/or scarred, resulting in a recurrence of symptoms and the need for a re-operation, does this occur with Durasis?
C:  During a clinical study of this product during which 59 patients received Durasis, 29 patients underwent surgery for treatment of Chiari. Follow-up in these patients ranges from three months to three years, and there have been no reports of reoperation attributed to Durasis. Reintervention in a small number of patients has shown no evidence of thickening, stiffness, or scarring. Additionally, no pathological thickening, stiffening or scarring has been seen in thousands of clinical implants of the same material used in DURASIS for many other uses.

How do you ensure that no disease or pathogens are passed from the animal into a patient?
C:  Numerous steps in the manufacturing of DURASIS ensure its safety. DURASIS is obtained from the small intestinal submucosa (SIS) of pigs raised under strict conditions. Then the SIS undergoes a patented process to remove living cells to help ensure that no pathogens are present in the tissue. Pathogenic organisms, including viruses, are eliminated during these processes, as proven by extensive testing of worst-case scenarios. Finally, the DURASIS is terminally sterilized with ethylene oxide gas following double packaging, to further prevent the risk of disease transmission.

How long did it take to develop this product?
C:  University researchers first discovered that the small intestinal submucosa (SIS) of pigs had unique capabilities to assist tissue repair in the late 1980’s. Since that time, numerous researchers, engineers, and physicians have worked together to bring several medical products based on this material to market. The development of clinical devices took seven years, and the more stringent development of a clinical device for the brain, DURASIS, took several more years.

How much does a unit of Durasis cost?
C:  Pricing varies based on sizes. This product has not been officially launched at this time therefore pricing is not yet available.

There has been a lot of controversy surrounding the marketing of a drug – Neurontin – that many people with Chiari and syringomyelia use; how do you market and sell a product like Durasis to the medical community?
C:  Drugs are often marketed for one purpose and then get used for other, “off label” uses. Durasis is a device specifically intended for the uses being promoted by COOK. Marketing and sales are a combined effort with a direct sales force in the field educating surgeons on the use and applications of Durasis in their practice.

Specifically, why should Durasis be used instead of a bovine, cadaver, or synthetic graft?
Disease transmission risk associated with the use of bovine or cadaver tissue is a big concern that has eliminated many dural substitute products from the market outside of the United States. DURASIS, because it is derived from pig tissue, does not carry the extent of disease transmission risk associated with these other tissue sources. DURASIS is the first medical device for the brain and spinal cord based on the remodeling and replacement technology of a collagen scaffold material. Unlike permanent synthetic substitute materials, DURASIS is a natural biomaterial that takes on the cellular characteristics of surrounding dural tissue by serving as a scaffold on which human tissue grows. This means that no foreign piece of plastic or leather-like material will remain indefinitely in the surgical site. Instead, the DURASIS device will gradually be replaced with your own tissue leaving nothing foreign behind. As the biomaterial is replaced with new tissue, the scaffold is no longer needed and is absorbed by the body. This eliminates the risk of prolonged inflammation, graft rejection, and infection – complications commonly associated with synthetic materials.

Some neurosurgeons have suggested that to avoid complications for Chiari surgeries, the graft should be taken from the patient’s own body. Is Durasis better than a graft from the patient’s own body?
C:  Grafts taken from the patient, autografts, necessarily create a tissue defect at the harvest site. Often this harvest site can have complications of its own, and many patients do not have suitable sites on their body for harvesting such a graft. When DURASIS is used for Chiari surgeries, it can address the need for a tissue replacement without creating a tissue deficit, pain at the harvest site, and potential infection risk elsewhere on the patient.

What enhancements and/or future products do you have planned?
C:  COOK is always looking to new developments in the market and working with physicians and surgeons to address the needs of patients and physicians through market research, product development, and product improvement. Future products may address more specific surgical procedures or be sized to facilitate placement by the surgeon in specific areas of the brain and spinal cord.
 

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In the Spotlight:

COOK Incorporated

• Specializes in minimally invasive medical devices and technologies for diagnostic and therapeutic procedures

• Founded in 1963

• Headquarters in Bloomington, IN

• Manufactures more than 50,000 products

• Divisions include:  Critical Care, Surgical, Biotech, OB/Gyn, Urology, Vascular, Endoscopy, Gastroenterology, Wound

• Cook Biotech was formed in conjunction with Purdue University to develop commercial medical products from natural tissue sources

• www.cookgroup.com

• www.cookbiotech.com