Rat Laminectomy Model Research Articles

The effects of ankaferd blood stopper and microporous polysaccharide hemospheres on epidural fibrosis in rat laminectomy model.

To investigate whether topically administered hemostatic agents ankaferd blood stopper and microporous polysaccharide hemospheres can decrease epidural fibrosis after laminectomy in rats. Eighteen adult male Sprague-Dawley rats were equally and randomly divided into three groups. In the treatment groups, ankaferd blood stopper and microporous polysaccharide hemospheres topically administrated upon duramater surface after laminectomy. Fibroblast count, epidural fibrosis and arachnoidal involvement were evaluated and graded histopathologically. Our data revealed that the count of fibroblasts, the grading of epidural fibrosis and arachnoideal involvement in the rats treated with microporous polysaccharide hemospheres were significantly less than the control group. Although the arachnoideal involvement in ankaferd blood stopper group were significantly less than the control group, there were no statistical differences when comparing the grading of epidural fibrosis and the fibroblasts count between the treatment groups and the control group. The ankaferd blood stopper and microporous polysaccharide hemospheres reduced epidural fibrosis and arachnoideal involvement after laminectomy in rats.

In situ forming hydrogel composed of hyaluronate and polygalacturonic acid for prevention of peridural fibrosis.

Hyaluronic acid-based hydrogels can reduce postoperative adhesion. However, the long-term application of hyaluronic acid is limited by tissue mediated enzymatic degradation. To overcome this limitation, we developed a polygalacturonic acid and hyaluronate composite hydrogel by Schiff's base crosslinking reaction. The polygalacturonic acid and hyaluronate composite hydrogels had short gelation time (less than 15 s) and degraded by less than 50 % in the presence of hyaluronidase for 7 days. Cell adhesion and migration assays showed polygalacturonic acid and hyaluronate composite hydrogels prevented fibroblasts from adhesion and infiltration into the hydrogels. Compared to hyaluronate hydrogels and commercial Medishield™ gels, polygalacturonic acid and hyaluronate composite hydrogel was not totally degraded in vivo after 4 weeks. In the rat laminectomy model, polygalacturonic acid and hyaluronate composite hydrogel also had better adhesion grade and smaller mean area of fibrous tissue formation over the saline control and hyaluronate hydrogel groups. Polygalacturonic acid and hyaluronate composite hydrogel is a system that can be easy to use due to its in situ cross-linkable property and potentially promising for adhesion prevention in spine surgeries.

Comment on Bolat et al.: Investigation of efficacy of mitomycin-C, Sodium Hyaluronate and Human Amniotic Fluid in Preventing Epidural Fibrosis and Adhesion Using a Rat Laminectomy Model.

Dear Editor, This letter is written in response to a recently published report by Bolat et al. [1] regarding mitomycin-C, sodium hyaluronate and human amniotic fluid in preventing epidural fibrosis and adhesion using a rat laminectomy model, which published in December 2013 in the Asian Spine Journal. In this study, the authors evaluate the effects of two treatments, mitomycin-C, sodium hyaluronate and human amniotic fluid, on preventing spinal epidural fibrosis. They concluded that implantation of mitomycin-C, sodium hyaluronate and human amniotic fluid reduces epidural fibrosis and adhesions after spinal laminectomy in rat models. Although this is a highly useful study, there are several issues that deserve further clarification by the authors. First, we wanted to inquire how the mitomycine-C, sodium hyaluronate or human amniotic fluid was dissolved? This is an important question because different vehicles mayaffect the results. Second, the authors should give more detailed information about the dosage or density of sodium hyaluronate and human amniotic fluid used in the study. This information would be helpful in further research efforts. Third, according to the description found in the articles Materials and Methods section, authors applied mitomycine-C on the operation level topically and waited for three minutes. However, the time of topical application of sodium hyaluronate and human amniotic fluid is just three minutes? We appreciate the authors' important contribution to this field of study, including supplying us with additional information in preventing epidural fibrosis. However, many studies such as the optimal concentration of different agents, the safety of agents and so on are needed in further studies for clinical practice.

Letter to the editor: investigation of efficacy of mitomycin-C, sodium hyaluronate and human amniotic fluid in preventing epidural fibrosis and adhesion using a rat laminectomy model.

The article entitled Investigation of Efficacy of Mitomycin-C, Sodium Hyaluronate and Human Amniotic Fluid in Preventing Epidural Fibrosis and Adhesion Using a Rat Laminectomy Model published in the Asian Spine Journal highlights an important problem for spinal surgeons [1]. We are thankful to the authors for their comments and informative letter, which highlights the doses which might be helpful in further research. The authors are right because using different dissolving methods can affect the results, but we didn't add any dissolving solution. Regarding the second point about dosage and density, we used a 0.01% mitomycin C solution [2] (an instant preparation that is usually used for ophthalmologic disorders) and 0.1 mL sodium hyaluronate [3]. Referring to the last question about the duration time, all of the drugs were applied 3 minutes. We hope those information are helpful and may encourage further research.

Use of decorin to prevent epidural fibrosis in a post-laminectomy rat model

The formation of epidural fibrosis adjacent to the dura mater is a complex multi-step process that is associated with a marked reduction in tissue cellularity and the excessive deposition of extracellular matrix components. Extensive epidural fibrosis is a major cause of post-laminectomy syndrome. Decorin strongly inhibits fibrosis formation in various tissues via blockade of transforming growth factor-β1. The aim of this study was to investigate the effects of a topical application of decorin on the formation of epidural fibrosis in a rat laminectomy model. Twenty-four female Wistar albino rats (250–350g) were equally and randomly divided into three groups (control, spongostan and decorin). Laminectomy was performed between the L3 and L5 levels in all rats. The dura mater was directly exposed to spongostan soaked with saline (2cc/kg) or decorin (100µg/kg). Four weeks later, the laminectomized spine of the rats was completely removed between the L3 and L5 levels. The extent of the epidural fibrosis and arachnoidal involvement was histopathologically evaluated and graded. Our data revealed that epidural fibrosis was significantly reduced in the group treated with decorin compared to the spongostan and control groups (P<0.05).Our study demonstrates that the topical application of decorin can be effective in reducing the formation of epidural fibrosis in a simple laminectomy rat model.

Reduction of epidural fibrosis and dural adhesions after lamina reconstruction by absorbable cement: an experimental study

Background contextPost-laminectomy epidural fibrosis complicates revision spine surgery and is implicated in cases of “failed back syndrome.” Several materials have been used to minimize epidural fibrosis with varying results. PurposeThe aim of this study was to examine the impact of reconstruction of laminectomy site with a type of absorbable cement (Jectos) to reduce epidural fibrosis. Study designThis investigation is an experimental controlled study, which is designed to evaluate the preventive effects of laminectomy site reconstruction in rat laminectomy model. MethodsTwenty wistar rats were included in this study and divided randomly to two equal groups, namely, subject and control. In both groups, laminectomy was performed in L2 and L4 levels. Control group received no additional treatment. In the subject group, L4 levels were reconstructed by Jectos and L2 levels were non-reconstructed as internal controls. Six months after surgery the rats were sacrificed and the dural adhesion and epidural fibrosis were evaluated macroscopically and microscopically. The study was financially supported by Brain and Spinal Cord Injuries Repair Center. None of the authors have any conflict of interest. ResultsNon-reconstructed levels in both groups showed dense epidural fibrosis with marked dural adherence. L4 reconstructed levels in subject group showed reduced epidural fibrosis macroscopically (p=.024) and microscopically (p=.041). No foreign body reaction or ossification occurred at reconstructed sites. ConclusionsIn the present study, lamina reconstruction with absorbable cement was a safe method that significantly reduced post-laminectomy epidural fibrosis and dural adhesions in rat laminectomy model.

Investigation of Efficacy of Mitomycin-C, Sodium Hyaluronate and Human Amniotic Fluid in Preventing Epidural Fibrosis and Adhesion Using a Rat Laminectomy Model

Study DesignA retrospective study.PurposeThe aim of this study was to evalute the effects of mitomycin-C, sodium hyaluronate and human amniotic fluid on preventing spinal epidural fibrosis.Overview of LiteratureThe role of scar tissue in pain formation is not exactly known, but it is reported that scar tissue causes adhesions between anatomic structures. Intensive fibrotic tissue compresses on anatomic structures and increases the sensitivity of the nerve root for recurrent herniation and lateral spinal stenosis via limiting movements of the root. Also, neuronal atrophy and axonal degeneration occur under scar tissue.MethodsThe study design included 4 groups of rats: group 1 was the control group, groups 2, 3, and 4 receieved antifibrotic agents, mitomycin-C (group 2), sodium hyaluronate (group 3), and human amniotic fluid (group 4). Midline incision for all animals were done on L5 for total laminectomy. Four weeks after the surgery, the rats were sacrificed and specimens were stained with hematoxylin-eosin and photos of the slides were taken for quantitive assesment of the scar tissue.ResultsThere was no significant scar tissue in the experimental animals of groups 2, 3, and 4. It was found that there was no significant difference between drug groups, but there was a statistically significant difference between the drug groups and the control group.ConclusionsThis experimental study shows that implantation of mitomycin-C, sodium hyaluronate and human amniotic fluid reduces epidural fibrosis and adhesions after spinal laminectomy in rat models. Further studies in humans are needed to determine the complications of the agents researched.

The effectiveness of poloxamer 407-based new anti-adhesive material in a laminectomy model in rats

In the laminectomy model in rats, to verify anti-adhesive effectiveness of the new material, a mixture composed of poloxamer 407, calcium chloride, and xanthorrhizol, we compared it with that of commercially used solution form anti-adhesive agent GUARDIX-SL, Biorane. A total of 108 Sprague-Dawley rats (SD rats) were divided equally into three groups: negative control group (NCG), positive control group (PCG), and experimental group (EG). After exposing the dura on L4 level, we closed the wound shortly after hemostasis, after administering the anti-adhesive agent. To evaluate effectiveness, 18 SD rats from each group were killed after 1 week of rearing. Nine were examined by grading of gross adhesion and the other nine, by grading of histological adhesion. The degree of adhesion in the remainder of 18 SD rats in each group was examined with the same method after four weeks of rearing. Comparing the degree of adhesion after growth for 1 week, the gross and histological adhesion of the EG was lower than that of the NCG. There was no statistical significance in the gross score (P = 0.63), but there was statistical significance in the histological score (P = 0.04). The EG showed similar or improved degrees of adhesion in comparison with the PCG. In comparison after growth for 4 weeks, although gross adhesion of the EG was not significantly lower than the NCG, histological adhesion was remarkably low in the EG (P = 0.01). The EG showed similar or improved degrees of gross and histological adhesion in comparison to that of the PCG. (P = 0.20, 0.07). The new anti-adhesive material showed similar or improved effectiveness with the existing agents for commercial use. This result suggests that the new anti-adhesive material will be a successful candidate as a future product for clinical use.

Immunomodulatory effectiveness of azithromycin in prevention of postlaminectomy epidural fibrosis

Objective: One of the important causes of failed back surgery is the extensive peridural fibrosis collecting in the surgical field after spinal surgeries. Today we know that inflammatory mechanisms mediated by the immune system of the body plays an important role in generation of fibrosis. Azithromycin, a macrolide antibiotic, has proven immunomodulatory effects in various diseases. This study aims to investigate the effects of azithromycin on peridural fibrosisMethods: Twenty-four Wistar rats received laminectomies before dividing them into three groups randomly. Animals of the control group received normal saline intraperitoneally while animals in the treatment groups received low (20 mg/kg) and high (80 mg/kg) doses of azithromycin intraperitoneally after surgical interventions. The amount of fibrosis, fibroblast density and inflammatory cell density were analyzed histologically.Results: Analysis demonstrated significantly reduced fibrosis, fibroblast density and inflammatory cell density in treatment groups compared to the control group. There was no difference between the treatment groups.Conclusion: Immune system plays critical roles in tissue repair and fibrogenesis. Results of our study demonstrated that azithromycin application reduced formation of peridural fibrosis in experimental laminectomy model in rats. Further studies with different dose regimes and different application routes are required to carry these results to an advanced level.

Effectiveness of the biophysical barriers on the peridural fibrosis of a postlaminectomy rat model: An experimental research

Long term results after surgical treatment of disc herniation have shown that epidural and/or peridural fibrosis formed during the healing process after surgical intervention. We conducted this experimental study to evaluation of the effectiveness of the bioresorbable barriers (ADCON-L and Seprafilm(®) Adhesion Barrier) on formation of the peridural fibrosis in rat model performed laminectomy. Thirty-two male Wistar albino rats 250-350g body weight were distributed into three groups (CONTROL, AL group received ADCON-L; SAB group received Seprafilm(®) Adhesion Barrier). A dorsal laminectomy at L3, L4, L5 was performed, and then except those of the CONTROL group, the experimental material was left on the dura mater. Six weeks later spinal column of all rats was totally removed between the T10 and L5 levels, and peridural fibrosis, and dural adhesions were evaluated histologically and graded. The results were compared statistically by using the chi-square (χ(2)) test. Also three random regions were examined, and the fibroblast cells were counted. The fibroblast count results were statistically analysed by using the One-Way ANOVA test. The variation of histopathological grades was statistically significant regarding the comparison of the all groups obtained from the χ(2) test (χ(2)=16.40; p=0.003). However, the variation in the mean values of the fibroblast count result was not statistically significant obtained from the One-Way ANOVA test (F=2.114; p>0.05). Our study results suggest that Seprafilm(®) Adhesion Barrier and ADCON-L can be effective in reducing the prevalence of the postoperative peridural adhesions in rat laminectomy model. On the other hand, the fibroblast densities of the experimental groups were not different between groups. So, we could say that these materials can act as a foreign body in long term period in rat.

The effect of methylene blue on peridural fibrosis formation after laminectomy in rats: an experimental novel study

Background context Despite progress in surgical techniques, some patients still face postoperative recurrence of pain, although the rate of successful outcomes is estimated to be approximately 70% and 86% after primary decompression spinal surgery. Recently, attention has been focused on peridural fibrosis (PF), which may be responsible for recurrent pain after laminectomy or discectomy. Methylene blue (MB) has been shown to prevent fibrosis formation in various tissues. Purpose The aims of this study were to investigate the effects of MB and assess the effects of different doses on the prevention of postlaminectomy fibrosis formation in a rat model. This preclinical model is a potential platform for future clinical trials to identify an effective agent for the prevention of clinically important epidural scar formation. Study design An established bilateral L5–L6 rat laminectomy model was used to evaluate postlaminectomy PF with macroscopic and microscopic analyses. Patient sample Seventy-five male adult white Sprague-Dawley rats that underwent laminectomy at the L5–L6 levels were divided into five groups of 15 rats each. Outcome measures Dissected specimens were evaluated macroscopically and microscopically by examiners who were unaware of the group assignment to record the presence or absence of PF formation. Methods Groups A and B served as controls and Groups C, D, and E received treatment. Group A (sham) underwent laminectomy, and Group B was treated with normal saline at the laminectomy site. Rats in Groups C, D, and E received 0.1 mL MB at concentrations of 0.5%, 1%, and 2%, respectively, at the laminectomy site. All rats were killed 4 weeks after laminectomy. The results were compared statistically with the nonparametric Kruskal–Wallis test and Poisson regression. Results Peridural fibrosis was found in five rats (33%) in control Groups A and B and in two rats (10%) in MB-treated laminectomy Groups C and D. The difference between control and MB groups was not statistically significant (p=.27). The preventive effect of MB on PF was not seen at the highest dose of MB (2%) in Group E. Severity of fibrosis was lower in Groups C (MB 0.5%) and D (MB 1%) than in Group E (MB 2%) (p<.01). Wound healing was not affected, and there was no cerebrospinal fluid leakage. No neurological deficits were seen. Conclusion Low doses of MB may be an effective agent in preventing PF formation after lumbar laminectomy in rats. Clinical significance and safety in human use are currently undetermined.

Use of pimecrolimus to prevent epidural fibrosis in a postlaminectomy rat model

Epidural fibrosis is the scar tissue formed over the dura mater after a laminectomy. Extensive epidural fibrosis may be an important underlying cause of failed back syndrome. Pimecrolimus, an ascomycin derivative, is one of the new classes of immunomodulating macrolactams and was specifically developed for the treatment of inflammatory diseases. This study examined the preventive effects of the local application of pimecrolimus in minimizing spinal epidural fibrosis in a rat laminectomy model. Thirty Wistar rats were divided into 3 equal groups: control, mitomycin C (MMC), and pimecrolimus groups. Each rat underwent a laminectomy at the L-3 lumbar level. In the experimental groups, a cotton pad soaked with MMC (0.5 mg/ml) or 5 mg pimecrolimus was placed on the exposed dura mater. No treatment was performed in the control group rats. Thirty days after surgery, the rats were killed and the dura mater thickness, epidural fibrosis, and arachnoidal involvement were quantified. The mean dura thickness was measured at 9.28 +/- 3.39 microm in the MMC group and at 8.69 +/- 2.32 microm in the pimecrolimus group, compared with 14.70 +/- 4.14 microm in the control group. In addition, the epidural fibrosis and arachnoidal involvement were reduced significantly in the treatment groups compared with the control group. In this animal model, it was shown that locally applied pimecrolimus effectively reduces epidural fibrosis and dural adherence in rats that underwent lumbar laminectomy. Mitomycin C was equally effective as pimecrolimus in reducing epidural fibrosis and dural adherence in this study.

Mitomycin C, 5-fluorouracil, and cyclosporin A prevent epidural fibrosis in an experimental laminectomy model

This study examined the preventive effects of the local application of mitomycin C (MMC), 5-fluorouracil (5-FU), and cyclosporine A (CsA) in minimizing spinal epidural fibrosis in a rat laminectomy model. Thirty-two 2-year-old male Wistar albino rats, each weighing 400 +/- 50 g, were divided into four equal groups: sham, MMC, 5-FU, and CsA. Each rat underwent laminectomy at the L5-L6 lumbar level. Cotton pads (4 x 4 mm2) soaked with MMC (0.5 mg/ml), 5-FU (5 ml/mg), or CsA (5 mg/ml) were placed on the exposed dura for 5 min. Thirty days after surgery, the rats were killed and the epidural fibrosis, fibroblast density, inflammatory cell density, and arachnoid fibrosis were quantified. The epidural and arachnoid fibroses were reduced significantly in the treatment groups compared to the sham group. Fibroblast cell density and inflammatory cell density were decreased significantly in the MMC and 5-FU groups, but were similar in the sham and CsA groups. The decreased rate of epidural fibrosis was promising. Further studies in humans are needed to determine the short- and long-term complications of the agents used here.

The effect of mitomycin C in reducing epidural fibrosis after lumbar laminectomy in rats

Extensive epidural fibrosis after lumbar spine surgery might be an important underlying cause of failed-back syndrome. Based on previously obtained data, the effect of mitomycin C (MMC) in a concentration of 0.1 mg/ml on spinal epidural fibrosis in a rat laminectomy model was investigated in a large series. Eighty adult Wistar rats underwent lumbar laminectomy. In 40 rats, MMC in a concentration of 0.1 mg/ml was locally applied to the laminectomy sites. No similar treatment was performed in the other 40 rats. At intervals from one to 12 weeks after laminectomy, both macroscopic and histological evaluations were performed. For radiological investigation, 10 rats underwent magnetic resonance (MR) imaging at 6 weeks postoperatively. Furthermore, the concentration of MMC in cerebrospinal fluid (CSF) and serum was determined 12 hours postoperatively in seven rats. Due to ease of absorption, high levels of MMC were rapidly detectable in serum, whereas the values obtained from the CSF were markedly lower. In the majority of MMC-treated laminectomy sites, epidural scarring was significantly reduced and dural adhesions were absent, in comparison with control sites (p < 0.001), as confirmed by MR images. Accordingly, the macroscopic dissection of epidural fibrous tissue to reexpose the dura mater was performed more easily and without severe bleeding in these rats. The healing of skin and the lumbar fascia was not affected, and dural leakage was not observed. All control sites showed dense epidural fibrosis with marked dural adherence. In this experimental model, it was shown that locally applied MMC in a concentration of 0.1 mg/ml effectively reduces epidural fibrosis and dural adherence without side effects in rats that underwent lumbar laminectomy.

The role of mitomycin C in reducing recurrence of epidural fibrosis after repeated operation in a laminectomy model in rats

Extensive peridural fibrosis after lumbar spine surgery may contribute to poor outcome and recurrent symptoms leading to repeated operation. Secondary procedures are considerably hampered by the presence of scar tissue. Moreover, after excision of the peridural scar, the fibrous tissue may recur, leading to unsuccessful surgical outcome. Mitomycin C (MMC), an alkylating antibiotic substance isolated from Streptomyces caespitosus, potentially suppresses fibroblast proliferation after surgical intervention. The authors investigated the effect of MMC on the reformation of epidural fibrosis in a laminectomy model in rats. Twenty-four Wistar rats underwent a repeated lumbar laminectomy 3 months after the first operation. In 12 rats, MMC in a concentration of 1 mg/ml was locally applied to the laminectomy site. No treatment was performed in the control group of the other 12 rats. All rats underwent clinical evaluation. Mobility ratings and any evidence of neurological deficit were recorded. Twelve weeks after the second operation, the animals were killed for histological examination. The extent of epidural fibrosis and dural adherence was evaluated. All MMC-treated animals showed reduced epidural scarring, compared with the control group. In nine MMC-treated rats (75%), dural adhesions were moderate. In contrast, all control sites showed dense epidural fibrosis with marked dural adherence. No side effects of the treatment were observed. In this experimental study, MMC in a concentration of 1 mg/ml locally applied significantly reduced recurrence of epidural fibrosis and dural adhesions without any side effects after repeated spinal surgery in a laminectomy model in rats.

Topical high molecular weight hyaluronan reduces radicular pain post laminectomy in a rat model

Topical high molecular weight hyaluronan reduces radicular pain post laminectomy in a rat model

Topical high-molecular-weight hyaluronan and a roofing barrier sheet equally inhibit postlaminectomy fibrosis

Topical high-molecular-weight hyaluronan and a roofing barrier sheet equally inhibit postlaminectomy fibrosis

흰쥐에서의 카르복시메칠셀룰로오스나트륨과 겔란검 혼합겔의 유착방지 효과

The aim of the present study was to investigate the efficacy of a mixed gel formulation composed of sodium carboxymethyl cellulose and gellan gum (Na-CMC gel) for the prevention of adhesions after laminectomy. The anti-adhesive effect of the Na-CMC gel was tested in a controlled randomized study using an animal model of lumbar laminectomy. The animals (60 female Sprague-Dawley rats) were randomly allocated into two treatment groups to receive the Na-CMC gel on the injured area or no gel (control). The incidence of adhesions and their grade were blindly evaluated at 4, 8 and 12 weeks after surgery. The amount of scar tissue and tenacity were grossly reduced by the Na-CMC gel at postoperative 4, 8, and 12 weeks. The mean adhesion scores were 0.75, 1.25, and 1.38 at 4, 8, and 12 weeks in the gel-treated group, respectively. No significant inflammatory reaction was observed and the healing of wound was not affected by the Na-CMC gel. The Na-CMC gel reduced the amount of scar formation and tenacity in rat laminectomy model without affecting the healing of operation wound and other complications. Therefore, the Na-CMC gel may be the potential to prevent postsurgical adhesions in clinical state.

A preclinical post laminectomy rat model mimics the human post laminectomy syndrome

Chronic low back pain with sciatica complicating post laminectomy surgery is poorly understood. It is likely that some aspects of persistent pain of the syndrome results from spinal facilitation in which there is lowering of pain excitation levels. A small animal preclinical model is needed that mimics the clinical condition to permit detailed studies of the underlying altered neurochemistry of the sensory pathways. We propose herein a rat laminectomy model containing the elements required for study of the neurobiology of the condition. The model consists of a surgical laminectomy that includes L5 spinal nerve manipulation and disc injury, elements necessarily employed in human disc herniation surgery. At 8 weeks post laminectomy the proposed model demonstrates paraspinous muscle spasm, tail contracture, behavioral pain behavior, tactile allodynia, epidural and nerve root scarring, and nerve root adherence by scar to the underlying disc and adjacent pedicle. Two underlying pain facilitation states are invoked in the clinical condition: (1) an inflammatory state required to achieve wound healing; and (2) a nerve injury state resulting from nerve manipulation and subsequent epidural scarring, spinal nerve scarring, and spinal nerve tethering to the adjacent disc and pedicle. Both pain facilitation states are active in the model.

A collagen-based sealant to prevent in vivo reformation of epidural scar adhesions in an adult rat laminectomy model

The authors investigated the effect of a collagen-based sealant, Gel Amidon Oxydé (GAO), in preventing the reformation of epidural scar adhesions in an adult rat model of laminectomy. Thirty-two adult Sprague-Dawley rats underwent a complete L5-6 laminectomy, after which the dura mater was exposed and the left adjacent L-4 and L-5 nerve roots were exposed. The surgical wound was then closed; 1 month later it was reopened. The epidural scar adhesions that developed were observed and carefully removed, leaving clean dura and nerve roots reexposed. In 16 experimental rats, GAO was placed onto the reexposed dura and around the nerve roots before it polymerized. No treatment was performed in 16 control rats. Postoperatively, all rats were healthy and without neurological deficit. The incisions healed within 1 week regardless of the treatment with the GAO. Three months after reoperation, magnetic resonance imaging revealed that important epidural adhesions were present in the control rats but not in the experimental rats. These findings were then confirmed by gross anatomical examination in which a white tissue layer was found over the dura without adhesions in the experimental animals, whereas significant epidural scar adhesions were demonstrated in the controls. Histological evaluation of the laminectomy site also showed that the peridural space in the experimental rats was larger than that in the controls. The authors found that GAO may be a safe and effective antiscarring adhesion biomaterial in vivo. When placed into the laminectomy site, GAO may prove beneficial in preventing the formation and reformation of epidural scar adhesions in humans.