What Is the Lamina Dura?

Chinese name: Artificial dura mater
Foreign name: Artificial Dura Mater

Nature: Bilayer membrane
Function: Human Meningeal Substitute

Principle of artificial dura mater

Artificial Dura Mater is a substitute for human meninges made from biological materials. It is used to repair dura or meningeal defects caused by craniocerebral, spinal cord injury, tumors and other craniocerebral diseases to prevent cerebrospinal fluid leakage. , Intracranial infection, encephalocele, cerebral adhesions and scars to restore their integrity. The artificial dura mater is sutured to the defect site, and the edge of the artificial dura mater is closed with a sealant to prevent the leakage of hydrocephalus from the incision suture. If not sutured, the artificial dura mater with a larger dura mater window is placed on the defect. Place the edge under the dura mater, and apply a layer of adhesive, such as n-butyl cyanoacrylate (code 504), at the junction of the two, to obtain better results and significantly shorten the operation time.

Technical requirements for artificial dura mater

The clinical requirements for artificial dura mater are: non-toxic, no adverse reactions to the body and brain tissue; smooth surface, non-adhesion to arachnoid and brain tissue; have a certain strength, elasticity and elongation; easy to disinfect and save. Therefore, the ideal dura mater repair material needs to have the following characteristics: Adequate material source and simple preparation process; Stable chemical properties, no acute inflammation reaction, no meningeal-brain adhesion; good histocompatibility, no toxic side effects, Does not produce immune response; good safety, no carcinogenic substances, does not spread viral diseases; good toughness; good compactness, no leakage.

Classification of artificial dura mater

In recent decades, many neurosurgeons have searched for some dura mater substitutes, which can be divided into two categories.

Absorbable graft

Including autograft and allograft, such as temporal muscle fascia, cranial periosteal membrane, fibrin membrane, allantoic membrane, amniotic membrane, dead dura mater, bovine tendon processed membrane, bovine pericardium, and domestically created Special tire membrane.

Non-absorbable substance

Including metal phase polymer compounds, such as gold foil, silver foil, stainless steel sheet, rubber film (the earliest application), Cellulum film, nylon, vinylon, Teflon (polytetrafluoroethylene), polyester silicone rubber film. However, the former will cause different degrees of inflammatory reactions, resulting in fibrosis and adhesion to the brain, and the latter will produce connective tissue hyperplasia to varying degrees. At present, the processed membranes made of bovine tendons and polyester silicone rubber membranes are more commonly used.

Autologous fascia

At present, there are several types of dura mater substitutes, each with its own advantages and disadvantages, while those widely used in clinical applications are taken from autologous materials. The autologous fascia has the characteristics of no rejection and good histocompatibility. However, the autologous fascia has the disadvantages of requiring separate surgery for the extraction of the autologous fascia, the limited source of the material, and the degree of adhesion to the brain, which easily causes epilepsy. No need to.

Allogeneic tissue

Such as lyophilized human dura. Its advantage is that it has the ultrastructure of normal human meninges, which can play a role in supporting and protecting brain tissues. However, the source of materials is limited, it is restricted by ethics, and it has the potential to infect viral diseases. It has been banned.

Allogeneic material

Such as cattle pericardium, pig peritoneum and so on. Its advantages are mild tissue inflammation, good meningeal integrity after repair, can effectively prevent cerebrospinal fluid leakage, has certain stretchability and elasticity, smooth surface, and is not easy to produce adhesion with surrounding tissues. However, glutaraldehyde used in the removal of heterologous protein antigenicity will leave some aldehyde groups in the material, which is not easy to completely remove, which will prevent cells from invading the implanted tissue, has certain toxicity, and the possibility of foreign body reactions.

Synthetic repair materials

Such as TachoComb, Vicryl and so on. Such materials are generally easy to obtain and inexpensive, but as permanent foreign bodies, rejection reactions are difficult to avoid, which can easily cause aseptic inflammation and stimulate granulation tissue formation.

New products of artificial dura mater

Silk fibroin membrane

Silk fibroin is a silk protein. It belongs to the same structural protein as skin collagen, and its material sources are abundant and easy to process. Kim et al. Used silk fibroin membranes to repair dura mater in rat models of dura mater defect, and conducted a series of studies on its cytotoxicity and anti-inflammatory effect. The results showed that the silk fibroin membrane had no cytotoxicity, and could effectively reduce the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), while reducing the inflammatory cytokines IL-1, The expression of IL-6 and tumor necrosis factor- (TNF-) did not cause cerebrospinal fluid leakage after dura mater repair in rats. Some scholars have made silk fibroin into electrospun nano-fibroin fibers, and compared and studied their physical and chemical properties, morphology (fineness and porosity of fibers), structural stability and biocompatibility. It can be used in biomedical engineering such as tissue repair and regeneration. As a new type of silk fibroin membrane, its long-term impact needs to be further verified. In addition, how to better control its biomechanical properties, pore size, porosity, and degradation rate to meet the requirements of dura mater tissue self-repair needs to be further improved Extensive and in-depth exploration.

Amniotic membrane

The amniotic membrane is the innermost layer of the placenta. Its surface is smooth, free of blood vessels, nerves and lymphoid tissues. It has a certain elasticity and is about 0.02 to 0.5 mm thick. Amniotic membrane is less immunogenic and has anti-inflammatory effects. The amniotic membrane preserved by lyophilization can still maintain its histological structure, with an average number of pores of 2 × 106 / mm and a pore size of 0.3 to 0.4 m. It allows water and some small molecular substances to pass through, but it is generally difficult for bacteria to pass through diameters <5 m pores make it a barrier. Amniotic membrane contains active substances such as bacteriostatic factors, secondary lysosomes, and steroid hormone enzymes, which can effectively inhibit the growth of bacteria.

Tao et al. Compared the effects of lyophilized amniotic membrane, glutamine crosslinked amniotic membrane, and autologous free fat on reducing epidural scar adhesion after laminectomy. The results showed that glutamine cross-linked amniotic membrane can effectively reduce epidural scar fibrosis, reduce the amount and intensity of scar adhesion, and reduce postoperative complications. Hao et al. Wrapped the amniotic membrane around the transected nerve and found that it can effectively reduce the adhesion of nerves to surrounding tissues and the formation of scars, thereby retaining the migration of nerve cells and preventing traction injury and ischemia. Amniotic membrane meets the advantages of dura mater in many aspects, and it is expected to become an ideal dura mater.

Biocollagen Matrigel

Collagen belongs to the fibrous protein family and is the main component of animal extracellular matrix and connective tissue. There are many types of collagen, of which type is the most common. It exists in the skin, bones, and tendons. It has a slender, rigid molecule and a triple-helix structure formed by three collagen polypeptide chains. TissuDura is a collagen colloid extracted from the Achilles tendon. It is inactivated by sodium hydroxide and concentrated hydrochloric acid. It has no systemic or local toxicity, and the incidence of adhesion and infection is extremely low. Pettorini et al. Used TissuDura as a dura mater in 47 cases of pediatric neurosurgery. The results showed that it can effectively prevent cerebrospinal fluid leakage without inflammation and postoperative infection. Ciro et al., In a long-term imaging and neuropathological evaluation of their use in dura mater repair, believe that TissuDura is flexible, chemically inert, and adaptable, and is easy and fast to use. Surgical sutures were not required to reconstruct the dura mater with this fibrin glue, and no complications such as cerebrospinal fluid leakage, adhesions, and infections were observed. In addition, because the fibrin glue covering technology is simple and easy to operate, it can effectively shorten the operation time, and at the same time has certain transparency, which is conducive to the inspection of the surgical operation area, thereby reducing the risk of surgery.

Polymer materials

Expanded polytetrafluoroethylene (ePTFE) is a new medical polymer material. Sherman et al. Used ePTFE to repair the dura mater in the resection of the sphenoid region, with satisfactory results. Frank et al. Compared the effects of ePTFE and autologous periosteum in Chiari deformity type I duraplasty, and argued that ePTFE has more advantages in maintaining posterior cranial fossa space, improving spinal cavitations, and reducing the rate of surgical failure. Although some scholars believe that ePTFE material has higher surface tension and lower compliance, it will cause friction damage to the cerebral cortex, and the use in large areas may cause postoperative cerebrospinal fluid. However, the role of ePTFE as a substitute for hard films in small local areas is still worthy of recognition.

Xie et al. Applied polycaprolactone nanofibers to dura repair. Compared with the traditional non-radial arrangement of polycaprolactone nanofibers, it was found that the radially arranged fibers can guide and enhance the migration and reproduction of cultured cells from the periphery to the center more quickly. Dural fibroblasts cultured on these two types of fibers can express type I collagen (the main component of the extradural matrix of the dura mater), and their expression on radial fibers shows a high degree of regularity. The radial fibers are cluttered. This suggests that the structure of nanomaterials plays a key role in guiding tissue remodeling. Kurpinski et al. Prepared a double-layer nanofiber by electrospinning a poly-lactic acid--caprolactone / polypropanol solution, which is superior to collagen matrix in preventing cerebrospinal fluid leakage and promoting dural regeneration.

Bacterial cellulose membrane

Bacterial cellulose (BC) is a cellulose synthesized by Acetobacter during the fermentation and culture of Acetobacter. It has a fine natural fiber network structure composed of ultrafine fibers. The diameter of BC is only 10 nm to 80 nm. Nano fiber is the finest natural fiber. Bacterial cellulose has many unique properties, such as high crystallinity and high chemical purity, high tensile strength and elastic modulus, strong water binding, excellent shape maintenance ability and tear resistance, and high biological adaptability. And good biodegradability, and the performance and shape of bacterial cellulose can be adjusted during biosynthesis, that is, by adjusting the culture conditions, bacterial cellulose films with different physical and chemical properties can be obtained. These characteristics make bacterial cellulose widely used in food, medicine, and chemical industries. Dressings made of bacterial cellulose, such as Biofil and Bioprocess, have good therapeutic effects on skin burns and have been commercialized in some countries.

Bacterial cellulose membranes have many potential excellent conditions as artificial dura mater. Sanchez e Oliveira Rde and others compared the application of BC and human acellular dermal matrix in the repair of fetal sheep's spinal meningocele, and the results showed that BC can more fully cover the damaged nerve tissue and does not adhere to the surface of the nerve tissue. And deep, thereby reducing mechanical and chemical damage to the spinal cord. BC also has advantages in the treatment and avoidance of neural tissue adhesion during the operation.

Prospects of artificial dura mater

The above-mentioned new materials are more in line with the characteristics of ideal artificial dura mater materials, but they also have their own shortcomings. For example, the silk fibroin film still needs to be further improved in the manufacturing process; the amniotic membrane is in the material extraction method and cross-linking The choice of agents deserves further investigation; biocollagen does not have a certain spatial network structure, which is not conducive to the adhesion of fibroblasts; the biological toxicity and physical and chemical properties of polymer materials need to be confirmed by long-term tests; A new type of biomaterial has not been reported in the literature in the field of dura mater. Therefore, the mutual fusion of new materials and new technologies will become an inevitable way for the development and application of new dura mater replacement materials in the future.

Artificial dura mater extended reading

[1] Tao Xiaohu. Application of artificial dura mater in neurosurgery. China Tissue Engineering Research March 2012, Volume 16, Issue 12: 2217-2220

[2] Jiang Jian, Liu Zhijian, Wang Yan, et al. Materials and methods of dura mater reconstruction [J]. Journal of Clinical Neurosurgery, 2006, 3 (4): 167-169.

[3] Zhang Shiming, Liu Xiangyang, Li Mingzhong. Status and prospects of application research of dura mater repair materials [J]. Chinese Journal of Neurosurgery, 2003, 19 (5): 402-404.

[4] Liu Peng, Huang Shengping, Qi Songtao, et al. Experimental research on the application of biological artificial dura mater [J]. Journal of the First Military Medical University, 2004, 24 (11): 1242-1244.

[5] Yuan Peng, Fang Bo, Huang Tao, et al. Clinical study of biological artificial dura mater for repairing cerebral venous sinus [J]. Chongqing Medical Journal, 2011, 40 (16): 1566-1568.

[6] Zhou Yufeng, Huang Mei, Deng Congying, et al. Biocompatibility of artificial dura mater materials [J]. China Tissue Engineering Research and Clinical Rehabilitation, 2011, 15 (16): 2945-2948.

[7] Xu Chen, Chen Shiwen. Research and application of artificial dura mater [J]. International Journal of Neurology and Neurosurgery, 2011, 38 (4): 396-399.

[8] Wang Tiexia, Xu Xiping, Yang Jing, et al. Experimental study of artificial biofilm repairing dura mater defect [J]. China Journal of Modern Medicine, 2003, 13 (13): 108-109.

[9] Qin Guoqiang; Wang Guan; Yan Chengfen and others. The application of collagen sponge artificial dura mater in severe head injury [J] .. Chinese Tissue Engineering Research Chinese Tissue Engineering Research, February 2014. Volume 18 Number 8: 1307-1312

[10] Zhang Nianping, Fu Zhen, Wang Yuanfei, et al. Application of dura material materials in neurosurgery [J]. China Medical Innovation, 2010, 7 (2): 129-131.

[11] Yang Jian, Yang Jinxing, Mei Peidong, et al. Observation on the safety of biological artificial dura mater in decompression of traumatic large bone flaps [J]. Chinese and Foreign Medical Research, 2013, 11 (24): 12- 13.

[12] Li Wenhui, Wu Rile, Cen Lian. Research and clinical application of artificial dura mater repair material [J]. Tissue Engineering and Reconstruction Surgery, 2013, 9 (2): 113-115.

[13] Lu Xia, Wu Xuesong, Li Wen, et al. Status of clinical application of dural repair materials. Youjiang Medical Journal. 2008; 36: 349-51.