| The deficiency of natural dural tissue after intradural surgical procedures often necessitates a graft for optimal wound closure. Numerous natural and synthetic substitutes have been proposed, such as autografts, allografts, xenografts and nonabsorbable or absorbable polymer sheets. But while autologous tissue can be harvested from various anatomic sites, artificial dural substitutes can often save operative time and minimize morbidity.
Dural substitutes fall into two categories: absorbable and permanent. Although there are few commercially available absorbable dural substitute, there are a large number of products in the latter category, including various synthetic materials and processed allograft and xenograft tissues from various anatomic sites.
Three venders that offer synthetic dural substitutes are W. L. Gore & Associates, Inc., who offers the Preclude® Dura Substitute, Integra Neurosciences, who offers the DuraGen® Dural Graft Matrix, and Codman & Shurtleff, Inc., who offers the Ethisorb™ Dura Patch.
The Preclude® Dura Substitute from W. L. Gore & Associates is a non-biological membrane designed to seal around suture holes. Studies have shown minimal tissue attachment to the membrane with no foreign body reaction, making it an ideal temporary or permanent prosthesis. The Preclude Dura Substitute combines the proven performance of inert expanded polytetrafluoroethylene (ePTFE) with a comparably inert elastomeric fluoropolymer in a three-layer construct. The average porosity of the outer ePTFE layer is less than one micron, which provides excellent conformability and handling while minimizing fibrous tissue ingrowth. The elastomeric layer creates a watertight seal at the suture line. Additionally, after three to four months in vivo, the PRECLUDE Dura Substitute becomes translucent. When air molecules within the ePTFE structure diffuse into the surrounding aqueous environment, body fluid displaces the gas molecules and the material becomes translucent because of the similar index of refraction of the fluid and the ePTFE. This helps with the visualization of the underlying neural structures in cases requiring reoperation.
The Preclude Dura Substitute maintains its watertight character for the duration of its implantation because of its inert, non-absorbable material. Clinical studies have shown that the tight microstructure of the ePTFE surface is effective at minimizing tissue attachment. The microstructure prevents penetration by fibroblasts and other mesenchymal cells and thus minimizes dense fibrous ingrowth. The Preclude Dura Substitute is compatible with any non-absorbable suture with a non-cutting needle, such as a taper or piercing point. The Preclude Dura Substitute should be sutured in place using a tension-free technique. The Preclude is supplied sterile and requires no soaking or rinsing prior to use. In addition, clean, unused, and undamaged portions of the Preclude can be resterilized up to three times, using steam or ethylene oxide gas techniques. Resterilization does not compromise the mechanical or structural quality of the graft.
The DuraGen Dural Graft Matrix from Integra Neurosciences is an innovative collagen matrix for dural closure and an onlay graft for the repair of dural defects. DuraGen is fully resorbed following complete tissue closure of the dural defect. And is not encapsulated following neurosurgical implantation. DuraGen is soft, pliable, and molds instantly to the brain surface. Although tensionless stay sutures can be used if desired, suturing is not required. Also, DuraGen can be easily cut to fit dural defects of any shape or size. Some minimal adhesion formation can occur following significant disruption of pia-arachnoid and DuraGen has an infection rate comparable to other methods of dural closure. But the device is immunologically well tolerated as there were no foreign body reactions reported in any clinical trials. The collagen used to manufacture DuraGen is also used in the manufacture of a dermal regeneration template, absorbable hemostatic sponges, and absorbable wound dressings.
The Ethisorb Dura Patch from Codman & Shurtleff is a synthetic absorbable implant for the bridging of dura mater encephali and spinalis defects. It is a composed of a fleece of undyed Vicryl (Polyglactin 910) and undyed PDS (Poly-P-Dioxanon) and a PDS foil, dyed with D&C Violet No.2 (Color Index No. 60725). Because these materials are commonly used as suturing materials they have been extensively tested to prove their biocompatibility and non-toxicity. The porous structure of the Vicryl fleece allows tissue on-growth while the PDS film coating minimizes CSF leakage. Absorption is complete approximately 90 days after implantation.
The Ethisorb Dura Patch is pliable whether being used dry or wet. Because the implant is fully synthetic and sterilized by Ethylene Oxide, the risk of prionic disease transmittal is eliminated. .The implant requires no preparation time in comparison to some other devices. Also, using the Ethisorb Dura Patch can result in reduction in operation time compared to an autologous implant, which requires a second procedure for tissue harvesting.
The three synthetic dural substitutes mentioned here are effective at minimizing CSF leakage, are immunologically well tolerated, and are easy to use. Synthetic dural implants such as these should be close by during any subdural procedure.
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