Clinical experience with a novel bovine collagen dura mater substitute.

BACKGROUND: Dural substitutes are used to achieve a watertight closure in situations where adequate closure is not possible .This study was conducted to evaluate the efficacy and safety of use a new collagen matrix dural substitute ( Duradry, Tecnodry, Belo Horizonte MG) in repair or expansion of cranial and spinal dura-mater.
METHODS: 30 patients operated on between March and September 2008, were studied. Surgical logs were reviewed for sex, age, diagnosis, location of the graft, technique and presence of fistula or infection. The patients were followed-up for at least 3 months, and the presence of complications as cerebrospinal leakage, infection, aseptic meningitis, hydrocephalus, pseudomeningocele were analysed.
RESULTS: Only one patient presented with CSF fistula. No patients presented with wound infections, hydrocephalus, pseudomeningocele, meningitis, brain abscesses or signs of toxicity related to the material.
CONCLUSIONS: The new dural substitute used in this study is effective and safe, and the initial results are similar to those of other dural substitutes reported in the literature.

Introduction

The hermetic closure of the dura mater is essential to prevent a cerebrospinal fluid (CSF) fistula and its complications such as pneumocephalus, pseudo-meningocele, meningitis, hydrocephalus and so on, which are significant factors of morbidity and mortality[916].

In some cases, it is impossible to obtain dural closure in a water-tight manner because of dural retraction, extensive dural injury during the craniotomy or due to neoplastic invasion. In other patients, it is important to have an expansion of the dura mater, as in decompressive craniectomy and surgical treatment of Chiari malformations [7]. In such cases, the use of dural substitutes could be indicated.

This study is aimed at investigating the efficacy and safety of a new dural substitute, derived from bovine collagen (Duradry, Technodry, Belo Horizonte MG) in the peroperative repair or expansion of cranial and spinal dural.

Material and Methods

The present study was carried out at the neurosurgical department at Santa Casa Hospital of Belo Horizonte (Minas Gerais, Brazil) including 30 patients operated between March and September, 2008. The project was previously approved by the Ethics in Research Committee of the Hospital. The decision to perform a duroplasty was the assessment of the neurosurgical team during the procedure. Eleven pacients were male and 19 female, and age ranged between 18 and 76 years, with an average of 48.4 years.

All the patients included in this study were followed up in the postoperative period for at least 3 months except for 2 patients who died before this period. None of the deaths was directly related to the duroplasty. Distribution by sex, age, location of the graft, technique, and presence of fistula or infection in the postoperative period were analysed.

The graft is presented in two forms: film and sponge. The film is used whenever suture is possible, whereas the sponge is applied when suture is impossible, being used or not together with fibrin glue (TISSUCOL - Baxter). Table 1 shows the types of grafts and the technique used on the patients of this study. In most cases, the sponge graft was placed directly on the brain without glue or suture, covering the dural defect. In the five cases, film was used and the graft was fixed by stitches or completely sutured to the remaining dura mater. The choice of graft type and technique was decided by the surgical team during the surgery, according to the conditions of the surgical field.

The film was cut into a size and shape compatible with the dural defect and then sutured to the dura mater with 4-0 Prolene. The sponge was cut slightly larger than the dural defect and placed under or over the defect. Fibrin glue, was applied if necessary, on interface between the graft and the remaining dura mater.

All patients were followed up after discharge, on the 30th and 90th post-operative days. The presence of cerebrospinal fluid leakage, infection or new neurological deficits was investigated. Computerized tomography (CT) was performed in the postoperative period in all patients.

Results

Only one patient, operated on a Chiari malformation type I, presented with postoperative CSF fistula. None of the patients had wound infections, hydrocephalus, pseudomenigocele, meningitis or brain abscesses. No alterations were seen in the postoperative CT scans, such as pneumocephalus, dural thickening, or graft-related problems. Two patients died during the study period. One patient developed severe brain edema secondary to venous injury during surgery on a giant olfactory groove meningioma. The other patient, operated on an intraventricular tumor, died after bleeding in the posterior fossa right after the surgery. It is clear that neither of the deaths were related to the dural graft. Table 2 shows the topographic distribution of lesions treated. The average age of patients with supratentorial dural lesions was 57 years, different from the overall mean age of 48.4 years, pointing to age as a relevant factor when considering the need for duroplasty in the supratentorial location. It is also possible to notice that the need for duroplasty is considerably higher in the posterior fossa, as the dura tends to retract and therefore it is more difficult to obtain a water tight closure.

The indication for duroplasty was decided by the neurosurgical team during surgery. All patients participating in the study signed a term of informed consent prior to surgery. Table 2 shows the indications for the use of the implant Duradry in this series. The use of the heterologous graft facilitated the operation considerably, reducing the time and the need for new surgical incisions for the removal of grafts like fascia lata [1014]. In spinal surgeries, where it is usually difficult to suture a graft, the use of Duradry was also useful in reducing the surgical time and no fistula was observed in such cases [22].

There was only one CSF fistula in this series. It was during the surgical treatment of a Chiari malformation in which the matrix collagen graft was used. The patient developed a fistula and meningitis. The patient was treated with external lumbar drainage for 7 days and antibiotics. As the fistula remained, he was re-operated and a hole in the dura was found. A new film graft was used so as to close the fistula and the patient recovered well.

Discussion

Galea aponeurotica or fascia lata are the most usual autologous grafts used in duroplasty. In cases where it is not possible to use them, heterologous dural substitutes are needed. All dural substitutes, particularly the heterologous ones, may be the cause of potentially serious complications such as infections and inflammatory reaction to a foreign body. In the 1950's, lyophilized dura mater of cadavers was used, as it was easy to obtain and to handle. However, complications like prions infection made it impossible to keep it in use [24811131517182729].

Dural grafts obtained from various animal tissues. such as pericardium, intestinal mucosa and peritoneum. were progressively used and later abandoned, due to the risk of zoonoses transmission, particularly bovine spongiform encephalopathy[210]. Various synthetic materials have been developed for dural grafting[21303133]. In theory, those would be the ideal grafts due to the availability and standardization in production. However, several reports with the use of such grafts showed severe complications related to their non-incorporation and development of chronic inflammatory reactions, even though there are several synthetic dural grafts in use with good results [612].

More recently, dural substitutes made from animal purified collagen have been increasingly used with good results. These grafts are prepared in such a manner that they contain only chemically acellular collagen with no other animal protein. This reduces the potential antigenic and infectious risk [16222534]. The grafts based on animal collagen naturally have a network of fibrils that promotes adherence, growth and proliferation of fibroblasts which will incorporate the graft and produce a new dural coverage. The low antigenic potential tends to prevent adherence to the brain. The material used in this study is similar to some dural grafts already available in the market (Tissudura - Baxter, Duragen - Integra). Our goal was to demonstrate the ease of use, the quality as a dural substitute and the low incidence of reactions to this new dural substitute derived from acellular bovine collagen. In the present study, inflammatory reactions related to the use of the product were not observed, and no specific technical difficulty in its use or management was noticed. Regarding the prevention of CSF fistula, the result was also appropriate.

Conclusion

Our results show that the dural substitute used in this study is effective and safe. Longer follow up and a larger number of patients are necessary to confirm the absence of complications and adverse effects related to Duradry. However, we can conclude that the initial results of this new material are similar to those of other dural substitutes available in the market and reported in the literature.