Study and clinical application of a porcine biomembrane for the repair of dural defects

Histopathological Investigation of the Effectiveness of Collagen Matrix in the Repair of Experimental Spinal Dura Mater Defects

Objective

This study investigated the suitability of the collagen matrix as a dural graft in the repair of experimental spinal dura mater defects.

Materials and Methods

In the study, 30 New Zealand white rabbits were used. The rabbits were divided into a study and control group. In both groups, following exact laminectomy (Th 10 and 11) in rabbits under the isoflorane anesthesia, a spinal dural defect 1×0.5 cm in size was formed. In the study group, the dura mater defect was covered with collagen matrix; in the control group, the excised dura was sutured back to its original position. At the end of the follow-up period, the rabbits were sacrificed. In all subjects, the vertebral colon was excised completely, and it was fixed in 10% formaldehyde solution. Sections 3 pm thick were taken from the specimens, stained with hematoxylin and eosin, and examined under a light microscope. The stained sections were evaluated under light microscopy with regard to the cellular inflammatory response, fibroblastic proliferation, foreign body reaction, and capsule formation.

Results

The collagen matrix was completely absorbed, and it was easy to use since it did not require sutures. Foreign body reactions were minimal in the early period and were resolved entirely in the end. Inflammatory response against the collagen matrix was no greater than in the control group in which the dura was sutured primarily and then closed, eventually disappearing entirely, and no adhesion formation resulted. Collagen permits successful regeneration by combining with the dura mater. No capsule formation was observed in either group.

Conclusion

This study shows that collagen is suitable for duraplastic procedures and that it may be a useful agent in patients in whom the dura cannot be closed primarily due to retraction, constriction, or excision.

Reconstruction of Chronic Complicated Scalp and Dural Defects Using Acellular Human Dermis and Latissimus Dorsi Myocutaneous Free flap

We present reconstruction of a complicated scalp-dura defect using acellular human dermis and latissimus dorsi myocutaneous free flap. A 62-year-old female had previously undergone decompressive craniectomy for intracranial hemorrhage. The cranial bone flap was cryopreserved and restored to the original location subsequently, but necessitated removal for a methicillin-resistant Staphylococcal infection. However, the infectious nidus remained in a dermal substitute that was left over the cerebrum. Upon re-exploration, this material was removed, and frank pus was observed in the deep space just over the arachnoid layer. This was carefully irrigated, and the dural defect was closed with acellular dermal matrix in a watertight manner. The remaining scalp defect was covered using a free latissimus dorsi flap with anastomosis between the thoracodorsal and deep temporal arteries. The wound healed well without complications, and the scalp remained intact without any evidence of cerebrospinal fluid leak or continued infection.

Application of PLGA/type I collagen/chitosan artificial composite dura mater in the treatment of dural injury

To improve the safety of dura repair in neurological surgeries, a new poly (glycolide-co-lactide)/type I collagen/chitosan artificial composite dura mater was evaluated in a rabbit model with dura mater injury. Eighteen rabbits were randomized to 3 groups: rabbits with unclosed dura mater; rabbits with dura mater repaired by fascia and rabbits with dura mater repaired by the composite membrane. Modified combine behavior score were given at a series of time points and several cytokines were also determined to reflect the inflammatory conditions. Rabbits whose dura mater was repaired by composite membrane showed a similar recovery rate of neurological function and inflammatory condition compared with the rabbits whose dura mater was repaired by fascia. In addition, the rabbits with closed dura mater were better than ones with unclosed dura mater in the restore rate of neurological function as well as inflammatory reactions according to the statistical analysis. The new artificial membrane appears to be safe and efficient in the treatment of dura mater defect.

Investigation of the material properties of alginate for the development of hydrogel repair of dura mater

The collagenous dura mater isolates the brain from the external environment and requires a secure closure following invasive neurosurgery. This is typically accomplished by approximation of the dura mater via sutures and adhesives. In selected cases, however, large portions of dura mater require excision, necessitating a tissue replacement patch. The mild reaction conditions and long-term biocompatibility of alginate evince strong candidacy for these applications. This study investigates the potential of diffusion and internally gelled alginates for these applications. Specifically, we quantified the viscosity, gel rate, syneresis level, compressive strength, compressive modulus, complex modulus and loss angle in the context of dura mater repair. The ideal sealant would have a rapid cross-link speed, while the ideal dura mater replacement would have a low level of syneresis. Both applications require a compressive modulus of 20-100 kPa and a complex modulus of 1-24 kPa. The data collected in this study suggests that the use of 1.95 wt% 43 mPa s alginate with 200 mM CaCl(2) is sufficient for approximating the dural membrane for closure alone or in conjunction with suture. Alternatively, the use of 1.95 wt% 43 mPa s alginate with 100 mM CaCO(3) is sufficient for tissue replacement in large dural defects.

Collagen matrix duraplasty for posterior fossa surgery: evaluation of surgical technique in 52 adult patients

Object

Complete dural closure is not always possible following posterior fossa surgery, often requiring a graft to secure complete closure. The authors report their experience of using a collagen matrix as an onlay dural graft for repair of a posterior fossa dural defect.

Methods

A retrospective analysis was performed in 52 adult patients who had undergone collagen matrix duraplasty for the posterior fossa. Complications directly related to the dural graft, the presence or absence of hydrocephalus, and the role of closed suction wound drainage in relation to postsurgical pseudomeningoceles were analyzed.

Results

The indication for posterior fossa surgery was tumors in 32 patients, vascular abnormalities in 9 patients, and spontaneous cerebellar hemorrhage in 11 patients. Closed suction wound drainage was used in 23 patients (44.2%). Forty-eight (92.3%) of 52 patients had a dural defect > 2 cm. Nine (81.8%) of 11 patients with hydrocephalus required ventriculoperitoneal shunts. Complications of the surgery included pseudomeningoceles in 2 patients (3.8%; no closed suction wound drainage); superficial wound infections in 1 patient (1.9%; with closed suction wound drainage); and unexplained eosinophilia in 1 patient.

Conclusions

Duraplasty using a collagen matrix is safe and effective in the posterior fossa, and is easy to use and time efficient. Meticulous layered wound closure, the detection and effective control of hydrocephalus, and the use of closed suction wound drainage reduces complications related to collagen matrix duraplasty for the posterior fossa.

Novel Equine Collagen-Only Dural Substitute

Objective:

A watertight and meticulous dural closure is an essential step after intradural neurosurgical procedures. When such a task cannot be performed, dural replacement materials and other adjunctive measures can provide an effective barrier between the subarachnoid compartment and the extradural space.

Methods:

We present our experience with a novel collagen-derived dural substitute in a series of 114 patients undergoing a variety of neurosurgical procedures. The patients were clinically or neuroradiologically observed, for immediate and delayed local or systemic complications related to the implant. In three patients who underwent reoperation after decompressive duraplasty and craniectomy for bone flap repositioning, we performed biopsy of the dural implant for histopathological studies.

Results:

None of the patients experienced local or systemic complications or toxicity related to the dural patch. None of the patients experienced a postoperative cerebrospinal fluid fistula, except one patient who underwent an endoscopic endonasal transsphenoidal marsupialization of a large intrasuprasellar arachnoid cyst; the fistula required reoperation for cerebrospinal fluid fistula repair and intravenous antibiotic therapy for bacterial meningitis. Postoperative magnetic resonance imaging scans showed signs of severe inflammatory response in only one patient who did not present any postoperative clinical symptom or neurological deficits. Three patients underwent reoperation for bone flap repositioning after decompressive craniectomy; in all patients, the dural substitute appeared to have promoted satisfactory dural regeneration, as confirmed by the histological studies. Furthermore, in such patients, no or minimal adherence with the other tissues and the brain cortex was observed.

Conclusion:

This study demonstrates that the new collagen-only biomatrix is a safe and effective dural substitute for routine neurosurgical procedures. The absence of local and systemic toxicity or complications and the scarce promotion of adherences and inflammation make this material appealing for its use as a dural substitute, even in cases in which the necessity of reoperation is foreseen.

Collagen-only biomatrix as a novel dural substitute. Examination of the efficacy, safety and outcome: clinical experience on a series of 208 patients

OBJECTIVES

Dural replacement materials and other measures can provide an effective barrier between the subarachnoid compartment and the extradural space when a watertight closure of the patient's own dura is not possible.

PATIENTS AND METHODS

We evaluated the efficacy and safety of a novel collagen-derived dural substitute on a series of 208 patients undergoing a variety of neurosurgical procedures.

RESULTS

No patients experienced any local or systemic complications nor toxicity related to the dural patch. No patients experienced post-operative CSF fistula except for one. Post-operative MRIs showed signs of moderate inflammatory response in only one patient, who did not present any post-operative clinical symptom nor neurological deficits. Three patients underwent reoperation for bone flap repositioning after decompressive craniectomy: in these cases, the dural substitute appeared to have promoted a satisfactory dural regeneration, as confirmed by the histological studies. Furthermore, in such cases no or minimal adherences with the other tissues and the brain cortex was observed.

CONCLUSIONS

The new collagen-only biomatrix is a safe and effective dural substitute for routine neurosurgical procedures. The absence of local and systemic toxicity or complications, and the scarce promotion of adherences and inflammation, make this material appealing for its use as dural substitute even in cases when a needed re-operation is anticipated.

Fibrin glue and polyglycolic Acid nonwoven fabric as a biocompatible dural substitute

OBJECTIVE

A novel biocompatible dural substitute created using fibrin glue and polyglycolic acid nonwoven fabric was examined for closing ability and histology.

METHODS

A rabbit skin model of dural defect was repaired using fibrin glue-covered polyglycolic acid fabric without suture and subjected to a water leakage test to investigate closing ability. In addition, the dural defects created on 12 hemispheres in 6 beagle dogs were repaired with the dural substitute and subjected to macroscopic and histological examination of the dural substitute and adjacent tissue 1 and 2 months later.

RESULTS

The dural substitute showed a breaking pressure of 109.9 +/- 37.1 mmHg. Macroscopically, no cases of excessive granulation, infection, or liquorrhea, either on the dural substitute or surrounding tissue, were observed. Histology indicated favorable tissue replacement of the dural substitute with collagenous fiber, although slight foreign body reaction was associated with its absorption. There was no evidence for adhesion to the brain surface or influence on nerve cells.

CONCLUSION

Dural substitute created using fibrin glue and polyglycolic acid fabric is advantageous in that it exerts excellent closing ability without requiring suture and can replace biological tissue without causing incompatibility.

Nonsuture dural repair using polyglycolic acid mesh and fibrin glue: clinical application to spinal surgery

BACKGROUND

In spinal surgery, repair of the dura is difficult when it is torn or fragile or is ossified as in cases with ossification of posterior longitudinal ligament. We report our experience with a nonsuture dural repair technique in patients undergoing spinal surgery; it uses a dura substitute composed of polyglycolic acid (PGA) mesh and fibrin glue. Here, we report the efficacy and safety of nonsuture duroplasty using PGA mesh and fibrin glue (PGA-fibrin sheet).

METHODS

The artificial dura mater is composed of a PGA-fibrin sheet. The dural defect is covered with a patch sprayed with fibrin glue without suturing to the dura mater. We first evaluated this technique in an experimental study by performing water leakage tests. Between May 2001 and January 2005, we used it in 160 spinal surgeries that required intraoperative dura repair.

RESULTS

Our preliminary tests showed that the threshold for water pressure without leakage was 161 +/- 42 and 96.5 +/- 32 mm Hg when the unsprayed margin around the perimeter of the patch was 5 and 2 mm, respectively. Of the 160 operated patients, 10 (6.3%) experienced subcutaneous cerebrospinal fluid (CSF) leakage. Of these, 6 required a second operation; in the other 4, the CSF collection diminished spontaneously. There were no other complications such as allergic reaction, adhesion, or infection.

CONCLUSION

In combination with CSF diversion, the PGA-fibrin sheet is a viable alternative method for dural repair in spinal surgery.

Suturing technique and the integrity of dural closures: an in vitro study

OBJECTIVE

The watertight closure of the dura mater is fundamental to intracranial procedures in neurosurgery. Nevertheless, for any given operator and type of suture, it is still not certain which suturing technique affords the most watertight dural closure. We have developed a laboratory model that allows us to compare the pressures at which dural closures leak when different suturing techniques are used.

METHODS

Human cadaveric dura was secured to a glass cylinder filled with colored saline. By application of force to a bag of saline attached to the cylinder, the pressure at which sutured dural incisions leak can be recorded. Using this method, we have compared the closure of 2-cm dural incisions with 3-0 silk using the following techniques (10 per group): 1) interrupted simple, 2) running simple, 3) running locked, and 4) interrupted vertical mattress. We have also compared the closure of 1- x 3-cm dural windows with cadaveric dura and 3-0 silk using the same suturing techniques (10 per group).

RESULTS

The pressure at which 2-cm linear dural incisions leaked was significantly higher when they were closed with the interrupted simple suturing technique (P < 0.05). There was no significant difference among the different suturing techniques when they were used to close a 1- x 3-cm dural window with a duraplasty. Overall, the pressures at which sutured linear dural incisions leaked were higher than the pressures at which sutured dural windows closed with duraplasties leaked.

CONCLUSION

In the experimental model described, an interrupted simple suturing technique affords the most watertight dural closure for linear incisions, whereas no suturing technique proved advantageous for the closure of a duraplasty.

Evaluation of a novel propylene oxide—treated collagen material as a dural substitute

Object. The authors evaluated a new non—cross-linked, propylene oxide—treated, acellular collagen matrix for use as a dural substitute in rabbits. They then compared this material to a commonly used dural substitute as well as to native dura mater used during primary closure.

Methods. Forty-six rabbits were randomly assigned to eight groups of five or six rabbits each. These groups differed according to the type of closure material that was used during surgery (native dura, control dural substitute, or experimental dural substitute) and the duration of convalescence. At the end of the experiment, the tightness of the duraplasty was assessed in each live rabbit by continuous infusion of fluid into the cisterna magna until leakage was detected. The animals were killed and each specimen was sectioned and studied histologically. The authors found that the experimental dural substitute was safe in animals for this application, that it held sutures well, and that a watertight closure was usually achieved. There were fewer adhesions between the experimental material and neural tissue was less likely to adhere to the cranium than the control graft. Histological examination showed that the experimental material had slightly more spindle cells and vascularity than the control graft.

Conclusions. The experimental graft material has several features that make it an attractive candidate for use as a dural substitute.

Posterior atlantooccipital membrane for duraplasty. Technical note

The authors describe the use of autogenetic posterior atlantooccipital (PAO) membrane for duraplasty following after posterior cranial fossa surgery. The PAO membrane is routinely exposed for procedures of the posterior cranial fossa and merely needs to be dissected free of the underlying dura mater. Recently this membrane was obtained in several pediatric patients following procedures of the posterior cranial fossa such as duraplasty in case of Chiari I malformation. No postoperative complications were found at 6-month follow-up examination. The advantages of this intervention include less manipulation of muscle and fascia than that involved in other procedures and, therefore, seemingly less postoperative pain and the negation of issues inherent with foreign-body graft sources. The authors believe this structure to be of use as a dural substitute in small dural openings of the posterior cranial fossa.

Human dural replacement with acellular dermis: clinical results and a review of the literature

BACKGROUND

The search for the ideal dural replacement in the setting where autogenous tissues are unavailable or inadequate still persists. Because of the ability of acellular dermis (AlloDerm, LifeCell Corporation, The Woodlands, TX) to remodel itself into native tissue, this dynamic quality is hypothesized to occur when used as a dural replacement.

METHODS

We report the long-term outcome of a small cohort of patients who, to our knowledge, were the first patients to receive AlloDerm for dural replacement. In addition, to put these current findings in a historical perspective, we present a review of the literature for dural replacement.

RESULTS

Ten patients all successfully underwent duraplasty with AlloDerm with only one postoperative complication that was not related to the acellular dermal dural repair.

CONCLUSIONS

We contend that AlloDerm is a safe and viable option for dural replacement in cases in which autogenous tissues are either unavailable or insufficient for proper reconstruction.

Dural repair using acellular human dermis: experience with 200 cases: technique assessment

OBJECTIVE

Many craniotomies require a watertight dural closure. When primary dural repair is not possible, a graft is necessary. Autograft material is not always easily accessible or available, necessitating the use of other material. We performed 200 craniotomies using an acellular human dermal graft (AlloDerm; LifeCell Corp., The Woodlands, TX) to determine its suitability as a dural substitute.

METHODS

From June 1996 through March 1998, all patients at Allegheny General Hospital who required a dural substitute graft and in whom autograft harvest was impractical or impossible received the acellular dermal autograft. The running suture technique was used to form a watertight seal.

RESULTS

After follow-up for a minimum of 1 year, seven patients have required subsequent surgery. Three patients developed cerebrospinal fluid leaks that were repaired without removing the dermal graft. Four patients developed wound infections that required debridement. In each patient, the graft seemed to be uninvolved in the infectious process and was left in place. The patients were administered antibiotics postoperatively, and there have been no recurrent infections. No adhesion formation or scarring was noted around or underneath the graft in any patient.

CONCLUSION

AlloDerm is a reasonable alternative to the available dural graft materials. Its handling characteristics are similar to those of dura, it is biologically inert, and it does not produce adhesion formation.

Examination of the safety and efficacy of an absorbable dura mater substitute (Dura Patch) in normal applications in neurosurgery

BACKGROUND

The possibility of the transmission of Creutzfeldt-Jakob disease and slow virus infection (HIV) by cadaveric dura implants makes it necessary to find synthetic, absorbable substitute materials for plastic reconstruction of the dura mater. Dura-Patch is a bilayered composite of a dyed polydioxanone (PDS) foil and an undyed fleece of Polyglactin 910 (Vicryl) and PDS threads, known to be completely resorbable.

METHODS

The Dura-Patch was tested prospectively in 101 patients undergoing 75 supratentorial, 20 infratentorial, and 6 spinal operations in seven different neurosurgical departments. Fixation of the substitute was either by suturing, gluing, or both. The specific tissue properties were investigated considering biocompatibility, form, size, adaptability, fixation, scarring, and resistance to CSF tearing with the aid of hematologic and neurological parameters, CCT, and/or MRI scanning up to 6 months postoperatively.

RESULTS

A total of 76 of 101 patients completed the study (75%). The biocompatibility of the Dura-Patch with timely absorption of the implant material was excellent without exception. There was no notable local scarring and no infections. Transient CSF cushioning in 12.9% of the patients was in keeping with the normal range. The elasticity and flexibility of the Dura-Patch was rated as "good" in 90% and was still better when the size of the implant increased, with an overall rating of handling as "good" or "excellent" in 97% of all operations.

CONCLUSIONS

The new absorbable Dura-Patch showed itself to be suitable for both plastic dura reconstruction and plastic extension of the subdural space with primary, watertight, germproof closure in routine intracranial and spinal tumor removal.

Porcine small intestinal submucosa as a dural substitute

BACKGROUND

The continuing search for the ideal dural substitute is currently directed toward collagen preparations. Xenogeneic porcine small intestinal submucosa (SIS), a naturally occurring extracellular matrix rich in collagen, has been successfully used as a soft tissue graft in several body organ systems, including preliminary studies as a dural substitute in the rat.

METHODS

Eight dogs underwent temporoparietal craniotomy and dural resection with replacement by SIS. Five dogs had contralateral procedures without SIS grafting. Three dogs had contralateral SIS grafts placed 2 months after the initial procedure. Histologic assessment was obtained at 7, 30, 60, 90, and 120 days. Cerebrospinal fluid (CSF) cytological examination and routine serum chemistry preceded sacrifice.

RESULTS

Histologic evaluation showed initial graft infiltration by mononuclear round cells, spindle-shaped cells within an eosinophilic staining extracellular matrix, and neovascularity. Complete resorption of the graft was evident by 60 days. This pattern is consistent with the previously described incorporation and remodeling of the SIS graft at other sites. CSF cytology and routine serum chemistry at the time of sacrifice were normal. Response to repeat grafting was identical to that of initial exposure. There was no clinical or histologic evidence of sensitization or graft rejection. No evidence of adverse effect on the underlying cerebral cortex was observed.

CONCLUSIONS

Porcine small intestinal submucosa demonstrates a favorable biologic response as a dural substitute in the canine model. It is a promising biomaterial for dural replacement.

Use of ligamentum nuchae graft for dural closure in posterior fossa surgery. Technical note

The technique of harvesting the ligamentum nuchae and its use in posterior fossa surgery are discussed. By using this technique the author has avoided postoperative cerebrospinal fluid leakage in more than 200 procedures.

Efficacy and biocompatibility of a photopolymerized, synthetic, absorbable hydrogel as a dural sealant in a canine craniotomy model

OBJECT

A canine craniotomy model was used to evaluate the dural sealing efficacy and biocompatibility of a novel, synthetic, bioresorbable hydrogel.

METHODS

Bilateral craniotomies were performed in 24 dogs assigned to six survival periods. In each animal a parasagittal durotomy was created and then repaired. At the treatment sites the hydrogel sealant was applied over the dural repair and photopolymerized. The repair was tested for leaks to 20 cm H2O by using a Valsalva maneuver. At the control sites the incisions were sutured and tested for leaks only. After uneventful survival periods, the leak test was repeated in three of the four animals in each group. Bone-dura adhesion was evaluated, after which the dura and underlying brain were removed, fixed, and examined histologically. En bloc histological investigation was performed on a specimen obtained from the fourth animal in each group. Over a 56-day period, 18 treated sites were tested for leaks. A leak was detected at a site remote from that of the repair in one animal; this was excluded from analysis. Thus 17 of 17 treated sites remained free of leaks. On the control side of one animal, there was a leak from a new dural tear at the cranial end of the durotomy, which occurred when the bone flap was removed. This site was also excluded from analysis. Eleven of 17 leak-tested control sites remained free of leaks over the study period. Bone-dura adhesions occurred in 15 of 19 control sites and had a mean adhesion score of 1.37 (range 0-4), whereas adhesions occurred in 10 of 19 treated sites with a mean adhesion score of 0.84 (range 0-3). No cortical reaction was noted.

CONCLUSIONS

This novel hydrogel sealant is efficacious in sealing dural repair sites measuring up to 2 mm. Healing of the underlying dura is not compromised and exposed cortical tissue is not altered histologically.

Development of a dural substitute from synthetic bioabsorbable polymers

A new bioabsorbable composite sheet was developed to provide a substitute for the dura mater and was evaluated histologically and biomechanically using rats and rabbits. This composite, composed of two L-lactic acid-epsilon-caprolactone (50% L-lactic acid, 50% epsilon-caprolactone) copolymer films and a poly(glycolic acid) nonwoven fabric, displayed good mechanical properties and was completely absorbed 24 weeks after implantation in the back of rats. Histological evaluation of the composite sheet was undertaken by implanting it in 31 rabbits with dural defects and examining the sites of implantation 2 weeks to 26 months later. No infection, cerebrospinal fluid leakage, evidence of convulsive disorders, significant adhesion to underlying cortex, or calcification was noticed in any cases. In addition, the regenerated duralike tissue had a high pressure-resistant strength 2 weeks after implantation. The authors conclude that this new bioabsorbable composite sheet can be successfully used as a dural substitute.

New surgical technique for treatment of extraarticular knee ankylosis

Laboratory and clinical studies were conducted to evaluate a treatment regimen for extraarticular ankylosis of the knee. The study evaluated the use of a porcine biomembrane to prevent quadriceps adhesions. A canine model was studied to determine the cellular response to the membrane by evaluating biopsies at 3, 7, 14, and 21 days after surgery using light and scanning electron microscopy. The results showed that there was nonspecific inflammatory cell infiltration into the base (rough) layer of the biomembrane during the first few days, although fibroblasts were the dominant cellular response 7 days later. No significant tissue ingrowth was seen on the smooth (muscular interface) surface of the membrane. The clinical study applied the information gained from the canine model to a series of 23 patients who suffered from extraarticular knee ankylosis and who were treated with a surgical procedure in which the released interface between the femur and the muscle groups was protected with a piece of porcine biomembrane. Subjects were observed from 16 to 30 months (mean, 26 months) after surgery. An average increase in knee range of motion of 86 degrees was documented, and a 100% patient satisfaction rate was noted. The technique yields satisfactory results in terms of cost, range of motion, and postoperative pain.

Duraplasty with biosynthetic cellulose: an experimental study

In the search for a new synthetic substitute for the dura mater, the authors conducted a research study using 32 mongrel dogs divided into three groups. Group I animals (21 dogs) underwent a right-sided parietooccipital craniotomy and substitution of two 1-cm pieces of dura mater by two different grafts: one piece of biosynthetic cellulose (50 mu thick) and one fragment of temporal fascia. The animals were observed for 30, 90, or 180 days. Group II animals (five dogs) underwent a somewhat larger craniotomy, removal of a 2-cm piece of dura mater, and lesioning of the cortex made by a thin sharp forceps, which caused bleeding that was controlled by application of a thin film of cellulose (10 mu thick). Duraplasty was performed using a 50-mu-thick cellulose membrane to complete the procedure and the animals were observed over a period of 270 days. Group III animals (six dogs) underwent smaller (1-cm diameter) bilateral parietal craniectomy, which included additional covering of the dura on the left side with 50-mu-thick cellulose and a suture of temporalis muscle. This group was observed for 40, 60, 80, or 120 days. Transient mild clinical symptoms were observed during the early postoperative period. At autopsy, macroscopic examination demonstrated good acceptance of the grafts with few and moderate extradural fibrosis, which caused adherence of the implants to the bone fragment. No adherence to the cortex was observed. Microscopic examination demonstrated absence of graft adherence to the cortical surface even when the cortex was injured. The cellulose was enveloped by two layers of connective tissue, the external layer being thicker than the internal one. Cellulose fibers increased in thickness over time until 30 days and then decreased in thickness until 270 days. This decrease in thickness between 30 to 270 days was statistically significant (p < 0.05). The physical properties of biosynthetic cellulose and the low cellular reaction to its implantation qualify this material as a dural substitute. Additional long-term studies must be undertaken to complete this report.

Histology after dural grafting with small intestinal submucosa

BACKGROUND

The search for the ideal dural substitute continues, inasmuch as available materials have significant limitations. Xenogeneic porcine small intestinal submucosa (SIS) has been successfully used as a soft tissue graft in several body organ systems, and it was logical to evaluate its use as a dural replacement.

METHODS

Twenty rats underwent bihemispheric craniectomy with dural resection. SIS onlay grafting on one side was performed. Histologic assessment was obtained at 7 and 28 days after dural grafting and included descriptive evaluation and quantitative scoring of graft-site thickness, vascularity, and cellular density. The total scores for the respective groups were compared using the Student's t test, significance being accepted for a p value < 0.05.

RESULTS

Histologic evaluation showed graft infiltration by spindle-shaped mononuclear cells, deposition of connective tissue, and neovascularity. This pattern is consistent with the previously described incorporation and remodeling of the SIS graft at other sites. A significant difference between the histologic scores of the SIS graft site and control site was found at 7 days (3.4 +/- 0.8 versus 0.1 +/- 0.1) and at 28 days (4.6 +/- 1.1 versus 2.2 +/- 0.5). No evidence of adverse effect on the underlying cortex was observed.

CONCLUSIONS

The results of this preliminary study utilizing porcine SIS as a dural substitute are promising and therefore justify further chronic studies.

Glutaraldehyde as a fixative in bioprostheses and drug delivery matrices

The use of glutaraldehyde as a fixative in bioprostheses and drug delivery matrices is reviewed. The chemistry of glutaraldehyde cross-linking and its effect on the biological performance of a number of bioprostheses such as tissue heart valves, vascular grafts, pericardial patches, tendon grafts and drug delivery matrices are examined.

Experimental evaluation of peritoneum and pericardium as dural substitutes

Although many substances have been tested in the search for an ideal dural substitute, an entirely satisfactory material has still not been found. The authors report an experimental study involving the closure of dural defects in rabbits with biomaterials developed from pig peritoneum and pericardium. Macroscopic and histologic examination, performed over a period between 15 and 45 days after implantation showed slight or no adhesion between the graft material and the cortex. No infection, CSF leakage, fistula or toxicity was noticed. The results demonstrated that these biomaterials could be used as satisfactory dural substitutes.

A clinicopathological study of collagen sponge as a dural graft in neurosurgery

There is frequently a need for dural grafts to cover defects resulting from retraction, shrinkage, or excision following neurosurgical procedures. Several materials have been evaluated both experimentally and clinically, and then discarded. Collagen, in its various forms, continues to be an area of intense interest. In this study the authors examined the suitability of collagen sponge to effect dural repair. In a 5-year clinical study 102 collagen sponge implants were examined macroscopically and histologically. Graft encapsulation, neomembrane formation, delayed hemorrhage, and foreign body reactions were not found. The porous nature of the collagen sponge encouraged fibroblastic ingrowth and dural repair. Meningocerebral adhesions were present in 11 patients, all of whom had required significant cortical resection or had pia-arachnoid disruption during the initial surgery. Inflammatory cells were seen only in response to infection. Postoperative cerebrospinal fluid leaks developed in only three of 67 patients who underwent an intradural posterior fossa procedure. In a prospective arm of the study involving 459 patients, the wound infection rate using collagen sponge was 6.1%, which compared favorably (p = 0.67) with the 5.7% rate in a similar group of 637 patients in whom collagen sponge had not been used.

Immune response in hosts with cadaveric dural grafts. Report of two cases

The use of cadaveric human dura has been critical in the repair of dural defects since the dawn of neurosurgery. Reports in the literature of immune response to this type of graft have been extremely rare. Two patients are presented who received cadaveric dural implants with resulting meningeal signs and cerebrospinal fluid eosinophilia several weeks after surgery. Peripheral eosinophilia was present in one patient. The signs and symptoms resolved temporarily during corticosteroid therapy and permanently upon removal of the offending grafts. These cases illustrate that an immune-type reaction can occur with significant morbidity in patients receiving cadaveric dural grafts. A proposed mechanism for this response is discussed.

Experimental evaluation of collagen sponge as a dural graft

Early collagen products, when used as dural substitutes, promoted severe inflammatory responses and fell into disrepute. A more recent advance, collagen sponge, which is derived from bovine flexor tendons was used in this experimental study. Collagen sponge was surgically implanted as an onlay dural replacement graft following skull trephination and dural excision in 12 primates. Macroscopic, histological and electron-microscopical evaluations were performed at periods of 1, 3 and 9 months. This preliminary animal study indicated that collagen sponge is suitable to use as a graft since it does not induce any inflammatory response or adhesions in the absence of pia arachnoid injury. If forms an ideal scaffold for the early ingrowth of fibroblasts to effect dural repair.

Experimental evaluation of a collagen-coated vicryl mesh as a dural substitute

Dural substitutes must provide immediate restitution of a membranous covering for the brain without inducing any adverse reaction in the host or provoking adhesions to underlying nervous tissues. Ideally, the material should disappear completely and be replaced by tissues similar to the dura mater. In this study, parietal dural defects were created in 12 beagle dogs and closed with a vicryl mesh prosthesis made watertight by a film of bovine collagen. Clinical and biological tolerances were satisfactory. There was one case of early local infection. Gross and microscopic examinations performed between 7 days and 9 months after implantation showed degradation of the prosthetic mesh and connective tissue growth into the implant mimicking dura mater as early as 15 days after implantation. There was no attendant inflammatory reaction or cortical adhesions or other adverse reactions. The authors conclude that collagen-embedded vicryl mesh provides satisfactory biological function and compatibility when used as a substitute for dura mater in the dog.

Use of collagen film as a dural substitute: preliminary animal studies

Cadaver grafts, laminated metallic materials, and synthetic fabrics have been evaluated as dural substitutes. Use of cadaver tissues is limited by fear of transmission of infectious disease while use of synthetic materials is associated with implant encapsulation and foreign body reactions. The purpose of this study is to evaluate the use of collagen film as a dural substitute. Collagen films prepared from bovine skin were used to replace the dura of rabbits and histological observations were made at 16, 28, 42, and 56 days postimplantation. Controls consisted of dura that was removed and then reattached. Control dura showed no signs of inflammation or adhesion to underlying tissue at 16 and 28 days postimplantation. By 56 days postimplantation, extensive connective tissue deposition was observed in close proximity to adjacent bone as well as pia arachnoid adhesions. Implanted collagen film behaved in a similar manner to control dura showing minimal inflammatory response at all time periods. At 56 days postimplantation collagen film appeared strongly infiltrated by connective tissue cells that deposited new collagen. The results of this study suggest that a reconstituted type I collagen film crosslinked with cyanamide acts as a temporary barrier preventing loss of fluid and adhesion formation. It is replaced after approximately 2 months with host collagen with limited inflammatory and fibrotic complications. Further studies are needed to completely characterize the new connective tissue formed as well as long-term biocompatibility and functioning of a reconstituted collagen dural substitute.