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

Intervertebral Disc Degeneration: Biomaterials and Tissue Engineering Strategies toward Precision Medicine

Intervertebral disc degeneration is a common cause of discogenic low back pain resulting in significant disability. Current conservative or surgical intervention treatments do not reverse the underlying disc degeneration or regenerate the disc. Biomaterial-based tissue engineering strategies exhibit the potential to regenerate the disc due to their capacity to modulate local tissue responses, maintain the disc phenotype, attain biochemical homeostasis, promote anatomical tissue repair, and provide functional mechanical support. Despite preliminary positive results in preclinical models, these approaches have limited success in clinical trials as they fail to address discogenic pain. This review gives insights into the understanding of intervertebral disc pathology, the emerging concept of precision medicine, and the rationale of personalized biomaterial-based tissue engineering tailored to the severity of the disease targeting early, mild, or severe degeneration, thereby enhancing the efficacy of the treatment for disc regeneration and ultimately to alleviate discogenic pain. Further research is required to assess the relationship between disc degeneration and lower back pain for developing future clinically relevant therapeutic interventions targeted towards the subgroup of degenerative disc disease patients.

Topically Applied Cross-Linked Hyaluronan Attenuates the Formation of Spinal Epidural Fibrosis in a Swine Model of Laminectomy

Epidural fibrosis is an inevitable aspect of the postoperative healing process which is one of the causes of failed back surgery syndrome following spinal surgery. The aim of the present study was to examine the inhibitory effect of 1,4-butanediol diglycidyl ether-crosslinked hyaluronan (cHA) on spinal epidural fibrosis in a swine model. Epidural fibrosis was induced through conduction of hemi-laminotomy (L2 and L3) or laminectomy (L4 and L5), while L1 was assigned as the control group in six pigs. The cHA was applied to L3 and L5 surgical sites. MRI evaluation, histologic examination, expressions of matrix metalloproteinases (MMPs), and cytokines in scar tissue were assessed four months after surgery. cHA treatment significantly decreased the scar formation in both hemi-laminotomy and laminectomy sites. cHA also significantly increased MMP-3 and MMP-9 expression in scar tissue. Further, the epithelial-mesenchymal transition -related factors (transforming growth factor-β and vimentin) were suppressed and the anti-inflammatory cytokines (CD44 and interleukin-6) were increasingly expressed in cHA-treated sites. The current study demonstrated that cHA may attenuate spinal epidural fibrosis formation after laminectomy surgery by enhancing the expression of MMPs and anti-inflammatory pathways.

Hyaluronan in immune dysregulation and autoimmune diseases

The tissue microenvironment contributes to local immunity and to the pathogenesis of autoimmune diseases - a diverse set of conditions characterized by sterile inflammation, immunity against self-antigens, and destruction of tissues. However, the specific factors within the tissue microenvironment that contribute to local immune dysregulation in autoimmunity are poorly understood. One particular tissue component implicated in multiple autoimmune diseases is hyaluronan (HA), an extracellular matrix (ECM) polymer. HA is abundant in settings of chronic inflammation and contributes to lymphocyte activation, polarization, and migration. Here, we first describe what is known about the size, amount, and distribution of HA at sites of autoimmunity and in associated lymphoid structures in type 1 diabetes, multiple sclerosis, and rheumatoid arthritis. Next, we examine the recent literature on HA and its impact on adaptive immunity, particularly in regards to the biology of lymphocytes and Foxp3+ regulatory T-cells (Treg), a T-cell subset that maintains immune tolerance in healthy individuals. We propose that HA accumulation at sites of chronic inflammation creates a permissive environment for autoimmunity, characterized by CD44-mediated inhibition of Treg expansion. Finally, we address potential tools and strategies for targeting HA and its receptor CD44 in chronic inflammation and autoimmunity.

Ulinastatin attenuates neuropathic pain via the ATP/P2Y2 receptor pathway in rat models

Ulinastatin, a serine protease inhibitor, which has anti-inflammatory properties and neuroprotective effects, is used to treat acute inflammatory disorders. Recent evidence indicates that administration of ulinastatin alleviates pain in rat model of neuropathic pain (NPP). However, its effect on NPP and the underlying mechanism requires further study. In this study, we evaluated the role of intrathecal administration of ulinastatin in rats with sciatic nerve ligation and observed the effect of ulinastatin on the ATP/P2Y2 receptor pathway. We performed mechanical and thermal sensitivity measurements, immunohistochemistry and double-label immunofluoresence studies to evaluate P2Y2 receptor and adenosine 5'-monophosphate-activated protein kinase (AMPK) expression in the dorsal horn of the lumbar enlargement region of the spinal cord, and a luciferase assay for the detection of ATP levels in the cerebrospinal fluid. The results showed that ulinastatin prevented the development of mechanical allodynia and thermal hypersensitivity in the rat sciatic nerve ligation model. Ulinastatin reduced the level of extracellular ATP, down-regulated P2Y2 receptor and AMPK expression in the spinal dorsal horn of the chronic constrictive injury model. We found that increased expression of P2Y2 receptor in microglia was likely involved in the activation of microglia after nerve injury, and ulinastatin inhibited the abnormal microglia activation in the dorsal horn after nerve injury. These findings demonstrated that ulinastatin might be a potential and effective drug for the treatment of NPP via the suppression of the ATP/P2Y2 receptor pathway.

Therapeutic effect of epidural hyaluronic acid in a rat model of foraminal stenosis

PURPOSE

Since receiving a warning from the US Food and Drug Administration (FDA) about injection of corticosteroids into the epidural space having serious adverse events, we have sought alternative medications for injection at this site. Hyaluronic acid (HA) has anti-adhesive, anti-inflammatory, and lubricating properties, so could potentially be useful for spinal pain. The exact mechanism by which spinal stenosis develops is not fully understood, but is likely to involve inflammation. Therefore, we hypothesized that HA could have a therapeutic effect in spinal stenosis. This study evaluated the effects of epidural administration of HA on alleviation of pain in a rat model of foraminal stenosis.

MATERIALS AND METHODS

After creating the animal model, HA (HA group) or saline solution (S group) was administered via an epidural catheter. The paw-withdrawal threshold to mechanical stimulation and motor dysfunction were monitored for up to 21 days. Tissue was collected to evaluate the degree of adhesion, inflammation in the perineural area, and chromatolysis in the dorsal root ganglion (DRG).

RESULTS

The mechanical withdrawal threshold was restored in the HA group but not in the S group (P < 0.001). The HA group also showed less fibrosis (P = 0.026) and less chromatolysis (P = 0.002) than the S group.

CONCLUSION

HA administered epidurally had a therapeutic effect on the allodynia and hyperalgesia induced by chronic compression of the DRG.

Effects of Systemic and Local Interferon Beta-1a on Epidural Fibrosis

Study Design

Level 1 randomized controlled study.

Purpose

To investigate the effects of systemic and local interferon-beta-1a (IFN-β-1a) on prevention of epidural fibrosis using histopathological parameters.

Overview of Literature

Epidural fibrosis involves fibroblastic invasion of nerve roots into the epidural space. Formation of dense fibrous tissue causes lumbar and radicular pain. Many surgical techniques and several materials have been proposed in the literature, but no study has assessed the effect of IFN-β-1a on prevention of epidural fibrosis.

Methods

Forty-eight adult female Sprague-Dawley rats were divided into six groups of eight: sham group, control group, systemic 44 μg IFN-β-1a group and 22 μg IFN-β-1a group (after laminectomy and discectomy, 0.28 mL and 0.14 mL IFN-β-1a applied subcutaneously three times for a week, respectively), local 44 μg IFN-β-1a group (laminectomy and discectomy, followed by 0.28 mL IFN-β-1a on the surgical area), and local 22 μg IFN-β-1a group (laminectomy and discectomy, followed by 0.14 mL IFN-β-1a on the surgical area). All rats were sacrificed after 4 weeks and groups were evaluated histopathologically.

Results

Compared with sham and control groups, significantly less epidural fibrosis, dural adhesion, and fibroblast cell density were observed in the local and systemic 44 μg IFN-β-1a groups. No other differences were evident between the local and systemic groups.

Conclusions

IFN-β-1a is effective in preventing epidural fibrosis with systemic and local application.

Effects of a Temperature-Sensitive, Anti-Adhesive Agent on the Reduction of Adhesion in a Rabbit Laminectomy Model

OBJECTIVE

A common cause of failure in laminectomy surgery is when epidural, peridural, or perineural adhesion occurs postoperatively. The purpose of this study is to examine the efficacy of a temperature-sensitive, anti-adhesive agent (TSAA agent), Guardix-SG®, as a mechanical barrier for the prevention or reduction of peridural scar adhesion in a rabbit laminectomy model.

METHODS

Twenty-six mature rabbits were used for this study. Each rabbit underwent two separate laminectomies at lumbar vertebrae L3 and L6, left empty (the control group) and applied 2 mL of the TSAA agent (the experimental group), respectively. Invasive scar formation or inflammation after laminectomy was quantitatively evaluated by measuring the thickness of the dura, the distance from the surface of dura to the scar tissues, the number of inflammatory cells in the scar tissues at the laminectomy site, and the concentration of collagen in histological sections.

RESULTS

At 6 weeks postsurgery, the dura was significantly thinner and the distance from the surface of dura to the scar tissues was greater in the experimental group than in the control group (p=0.04 and p=0.01). The number of inflammatory cells was not significantly different in the two groups (p=0.08), although the mean number of inflammatory cells was relatively lower in the experimental group than in the control group.

CONCLUSION

The current study suggests that the TSAA agent, Guardix-SG®, could be useful as an interpositional physical barrier after laminectomy for the prevention or reduction of adhesion.

1,4-Butanediol diglycidyl ether-cross-linked hyaluronan inhibits fibrosis in rat primary tenocytes by down-regulating autophagy modulation

Epidural fibrosis, an inevitable part of the postoperative healing process, is one of the important causes of failed back surgery syndrome after spinal surgery. The aim of this study was to examine the inhibitory effect of a novel material 1,4-butanediol diglycidyl ether-cross-linked hyaluronan (cHA) on fibrosis in primary tenocytes. cHA inhibited migration, cell proliferation, and suppressed the expression of fibronectin, but not transforming growth factor-β, in primary tenocytes. cHA significantly increased matrix metalloproteinase-3 but decreased collagen-1 and microtubule-associated protein light chain 3-II expression in a dose-dependent manner compared with control groups. We therefore concluded that suppressing autophagy activity may be involved in the anti-fibrotic effect of cHA in primary tenocytes. Further, cHA may have the potential for preventing epidural fibrosis and subsequent failed back syndrome in patients with laminectomy in the future.

Efficacy of topical cross-linked hyaluronic acid hydrogel in preventing post laminectomy/laminotomy fibrosis in a rat model

Post-laminectomy/laminotomy epidural fibrosis (EF) has been implicated as an important cause of failed back syndrome (FBS). The various clinical approaches used to control EF yield mixed outcomes. Cross-linked hyaluronic acid hydrogel (cHA) was synthesized to increase mechanical stability and residence time. We evaluated the therapeutic attenuation of proliferative EF in laminectomy/laminotomy groups treated and not treated with cHA. A bilateral T11-L1 total laminectomy or unilateral T12 laminotomy was done on four groups (n = 10 each) of Sprague-Dawley rats and then histologically examined 2 months post-surgery: (I) laminectomy group treated with and (II) not treated with cHA, (III) laminotomy group treated with and (IV) not treated with cHA. The grade of EF, the diameters within the spinal canal, dura mater thickness, and the area of the epidural space, subarachnoid space, and conus medullaris space were assessed. The cHA-treated subgroups (I, III) had a significantly lower grade of EF, thinner dura mater, and larger epidural and subarachnoid spaces than did the control subgroups (II, IV) (p < 0.05). The cHA formed a solid interpositional membrane barrier that prevented invasive fibrosis, and also helped reduce pathological changes to the adjacent structures. In conclusion, topically applied cHA is effective for reducing EF.

Adhesion Prevention after Laminectomy Using Silk-Polyethylene Glycol Hydrogels

Laminectomy is a common operation in spine surgery to reduce spinal cord and nerve pressure. However, scar tissues often form in the spinal canal and adhere to the dura surface, resulting in low back pain postsurgery. In the present study, biodegradable silk-polyethylene glycol (PEG) hydrogels are evaluated for adhesion prevention after laminectomies in New Zealand rabbits, with nondegradable expanded polytetrafluoroethylene (ePTFE) membranes and saline as controls. No significant difference among the three groups is observed within 2 weeks. Silk is fully degraded within 6 weeks, leaving a gap separating the scar tissue and the dura mater. Severe dural scar adhesion form in the saline control group after 8 weeks, while no or mild adhesion is observed in the ePTFE membrane and silk-PEG hydrogel samples. Human dermal fibroblasts (HS-865-SK cells) are cultured in the silk-PEG hydrogel extracts and on top of gel surfaces. Compared to the controls of tissue culture plate (no silk) and sonicated silk hydrogels (no PEG), the proliferation of fibroblasts in both conditions is significantly reduced initially but resumes after 120 h, suggesting the surface properties of the hydrogels and local, temporal release of PEG accounts for the adhesion prevention observed in vivo in this study.

Effects of cross-linked high-molecular-weight hyaluronic acid on epidural fibrosis: experimental study

OBJECT

Epidural fibrosis is nonphysiological scar formation, usually at the site of neurosurgical access into the spinal canal, in the intimate vicinity of and around the origin of the radicular sheath. The formation of dense fibrous tissue causes lumbar and radicular pain. In addition to radicular symptoms, the formation of scar tissue may cause problems during reoperation. The authors aimed to investigate the effects of cross-linked high-molecular-weight hyaluronic acid (HA), an HA derivative known as HA gel, on the prevention of epidural fibrosis by using histopathological and biochemical parameters.

METHODS

Fifty-six adult female Sprague-Dawley rats were evaluated. The rats were divided into 4 groups. Rats in the sham group (n = 14) underwent laminectomy and discectomy and received no treatment; rats in the control group (n = 14) underwent laminectomy and discectomy and received 0.9% NaCl treatment in the surgical area; rats in the HA group (n = 14) received HA treatment at the surgical area after laminectomy and discectomy; and rats in the HA gel group (n = 14) underwent laminectomy and discectomy in addition to receiving treatment with cross-linked high-molecular-weight HA in the surgical area. All rats were decapitated after 4 weeks, and the specimens were evaluated histopathologically and biochemically. The results were statistically compared using the Mann-Whitney U-test.

RESULTS

Compared with the sham and control groups, the HA and HA gel groups showed significantly lower fibroblast cell density and tissue hydroxyproline concentrations (p < 0.05). There was statistically significant lower dural adhesion and foreign-body reaction between the control and HA gel groups (p < 0.05). Granulation tissue and epidural fibrosis were significantly lower in the HA and HA gel groups compared with the sham group (p < 0.05). There were no significant differences in any histopathological parameters or biochemical values between Groups 3 and 4 (p > 0.05).

CONCLUSIONS

Cross-linked high-molecular-weight HA had positive effects on the prevention of epidural fibrosis and the reduction of fibrotic tissue density. The efficacy of this agent should also be verified in further experimental and clinical studies.

Potential risk of mitomycin C at high concentrations on peripheral nerve structure

Although the local application of mitomycin C may prevent epidural adhesion after laminectomy, mitomycin C can induce neurotoxicity in optic and acoustic nerves at high concentrations. To determine the safe concentration range for mitomycin C, cotton pads soaked with mitomycin C at different concentrations (0.1, 0.3, 0.5, and 0.7 mg/mL) were immediately applied for 5 minutes to the operation area of rats that had undergone laminectomy at L₁. Rat sciatic nerves, instead of dorsal nerves, were used in this study. The results showed that mitomycin C at 0.1-0.5 mg/mL did not damage the structure and function of the sciatic nerve, while at 0.7 mg/mL, mitomycin C significantly reduced the thickness of the sciatic nerve myelin sheath compared with lower concentrations, though no functional change was found. These experimental findings indicate that the local application of mitomycin C at low concentrations is safe to prevent scar adhesion following laminectomy, but that mitomycin C at high concentrations (> 0.7 mg/mL) has potential safety risks to peripheral nerve structures.

Investigation of efficacy of mitomycin-C, sodium hyaluronate and human amniotic fluid in preventing epidural fibrosis and adhesion using a rat laminectomy model

Study Design

A retrospective study.

Purpose

The 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 Literature

The 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.

Methods

The 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.

Results

There 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.

Conclusions

This 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.

Effects of sodium hyaluronate and methylprednisolone alone or in combination in preventing epidural fibrosis

OBJECTIVE

Epidural fibrosis and leptomeningeal adhesion formation are common causes of failed back surgery syndrome (FBSS). We employed a rat model of lumbar laminectomy to evaluate the histopathological effects of sodium hyaluronate (HA) and methylprednisolone (MP) alone or in combination on post-laminectomy epidural fibrosis.

METHODS

Thirty-two male Sprague-Dawley rats were divided into four groups. All rats underwent three-level lumbar laminectomy. In the treatment groups, HA solution, MP, or a combination of both was applied locally to the epidural spaces of the laminectomy fields. No neurological deficits or pathological wound site changes were observed in any of the groups. At the end of the sixth week, all rats were sacrificed, and the laminectomy vertebral column areas were removed en-bloc. Specimens were evaluated by an expert neuropathologist according to histopathological criteria.

RESULTS

The results of the three treatment groups were separately compared with the control group to assess epidural fibrosis. Minimal reduction in the rate of epidural fibrosis was observed in the groups treated with HA or MP compared with the control group. However, no significant difference in epidural fibrosis was noted between the combined treatment group and the control group.

CONCLUSIONS

Our study showed that MP and HA, given separately, significantly reduce post-laminectomy epidural fibrosis; however, the combination of these drugs is not effective. Further investigation is needed to address the causative drug interactions.

Effects of low and high molecular weight hyaluronic acids on peridural fibrosis and inflammation in lumbar laminectomized rats

Background

Postlaminectomy peridural fibrosis is inevitable. Some studies have compared and identified the effects of high molecular weight hyaluronic acids (HMWHA) and low molecular weight hyaluronic acids (LMWHA) on peridural fibrosis in postlaminectomy animal models. However, no studies have been found that compare pain behaviors between hyaluronic acids or among hyaluronic acids and other solid materials. The purpose of this study was to examine the correlation between pain-related behaviors and histopathologic changes in laminectomized rats using various peridurally administered materials.

Methods

Forty male Sprague-Dawley rats, laminectomized at the L5 and L6 levels, were divided into four groups: group C, laminectomy only; group L, laminectomy and LMWHA application; group H, laminectomy and HMWHA application; group F, laminectomy and fat interposition. Pain behaviors were checked before, 3 days, 1 week, and 3 weeks after surgery. Histopathological changes were checked at the L5 level 3 weeks after the surgery.

Results

The 50% withdrawal thresholds in groups L and H were higher than that in groups C and F three days after laminectomy (P < 0.05). The paw withdrawal time did not change among the groups and in each group during the study period. Peridural fibrosis in group F was significantly lower than in the other groups (P < 0.05).

Conclusions

Hyaluronic acids significantly reduced mechanical allodynia but not thermal hyperalgesia. Peridural fibrosis did not show any correlation with pain behaviors. There have been limited studies on the correlation between peridural fibrosis and pain behavioral change, which should be verified by further studies.

The effect of hyaluronate-carboxymethyl cellulose on bone graft substitute healing in a rat spinal fusion model

OBJECTIVE

The aim of this study was to evaluate the impact of sodium hyaluronate-sodium carboxymethyl cellulose (HA-CMC), an anti-adhesive material for spinal surgery, on bone fusion by applying it to rat spinal models after lumbar posterolateral fusion.

METHODS

Lumbar posterolateral fusion was performed at L4-5 using bone graft substitutes in 30 rats. HA-CMC was injected in 15 rats at a dose of 0.2 cc (HA-CMC group) and a saline solution of 0.2 cc in the other 15 rats (control group). Simple radiographs were taken until postoperative 9 weeks with an interval of one week. At postoperative 4 and 9 weeks, three dimensional computed tomography (3D CT) scanning was performed to observe the process of bone fusion. At 9 weeks, bone fusion was confirmed by gross examination and manual palpation.

RESULTS

There were no statistically significant differences in bone fusion between the two groups. 3D CT scanning did not reveal significant differences between the groups. The gross examination and manual palpation after autopsy performed at 9 weeks confirmed bone union in 93.3% of both groups.

CONCLUSION

The anti-adhesive material used for spinal surgery did not have adverse effects on spinal fusion in rats.

Preparation and characterization of a new gellan gum and sulphated hyaluronic acid hydrogel designed for epidural scar prevention

Postsurgical adhesions are a common problem in clinical practice, causing nerve compression, pain and discomfort. A new hydrogel based on gellan gum and sulphated hyaluronic acid was synthesized, with the aim to create an effective barrier for epidural scar formation. Physico-chemical properties of the gel were analyzed, and preliminary biocompatibility data (i.e. cytotoxicity) have been collected in view of its potential clinical use. The characterization of the new material demonstrated that the hydrogel, due to its high-viscosity, could effectively act as a barrier with a long in situ residence time. In addition, the hydrogel can be easily extruded from a syringe and its structure exhibits excellent stabilizing properties. Furthermore, biological assays showed that this gel is suitable for further preclinical development.

Use of Temporary Implantable Biomaterials to Reduce Leg Pain and Back Pain in Patients with Sciatica and Lumbar Disc Herniation

The principle etiology of leg pain (sciatica) from lumbar disc herniation is mechanical compression of the nerve root. Sciatica is reduced by decompression of the herniated disc, i.e., removing mechanical compression of the nerve root. Decompression surgery typically reduces sciatica more than lumbar back pain (LBP). Decompression surgery reduces mechanical compression of the nerve root. However, decompression surgery does not directly reduce sensitization of the sensory nerves in the epidural space and disc. In addition, sensory nerves in the annulus fibrosus and epidural space are not protected from topical interaction with pain mediators induced by decompression surgery. The secondary etiology of sciatica from lumbar disc herniation is sensitization of the nerve root. Sensitization of the nerve root results from a) mechanical compression, b) exposure to cellular pain mediators, and/or c) exposure to biochemical pain mediators. Although decompression surgery reduces nerve root compression, sensory nerve sensitization often persists. These observations are consistent with continued exposure of tissue in the epidural space, including the nerve root, to increased cellular and biochemical pain mediators following surgery. A potential contributor to lumbar back pain (LBP) is stimulation of sensory nerves in the annulus fibrosus by a) cellular pain mediators and/or b) biochemical pain mediators that accompany annular tears or disruption. Sensory fibers located in the outer one-third of the annulus fibrosus increase in number and depth as a result of disc herniation. The nucleus pulposus is comprised of material that can produce an autoimmune stimulation of the sensory nerves located in the annulus and epidural space leading to LBP. The sensory nerves of the annulus fibrosus and epidural space may be sensitized by topical exposure to cellular and biochemical pain mediators induced by lumbar surgery. Annulotomy or annular rupture allows the nucleus pulposus topical access to sensory nerve fibers, thereby leading to LBP. Coverage of the annulus and adjacent structures in the epidural space by absorbable viscoelastic gels appears to reduce LBP following surgery by protecting sensory fibers from cellular and biochemical pain mediators.

Neurophysiological and histopathological evaluation of low-dose radiation on the cauda equina and postlaminotomy fibrosis: an experimental study in the rat

STUDY DESIGN

We evaluated the electrophysiological changes to the cauda equina after low-dose external irradiation in a postlaminotomy fibrosis model in rats.

OBJECTIVE

To clarify the immediate and long-term electrophysiological responses of antifibrotic radiation therapy in a fibrosis model.

SUMMARY OF BACKGROUND DATA

Low-dose perioperative radiation therapy inhibits scar formation. However, its efficacy for preventing fibrosis-induced compressive neuropathy and its potential adverse effect on underlying neural structures have not been studied.

METHODS

Twenty-four rats were placed in 3 groups of 8: group I, sham operation (laminar exposure alone) with a single fraction of 700 cGy external irradiation given using a 9-MeV electron beam 24 hours postsurgery; group II, left L5 hemilaminectomy (laminotomy) alone; and group III, left L5 hemilaminectomy with the same radiation protocol as group 1. We recorded mixed-nerve-elicited somatosensory-evoked potentials (M-SSEP)- and dermal (D)-SSEP at the thoracolumbar junction, and L1-L2 interspinous ligament after percutaneously stimulating the posterior tibial nerve at the bilateral medial ankle and L5 dermatomal fields. We compared the potentials recorded immediately before, 30 minutes, 2 weeks, and 1, 2, and 3 months after surgery on the operated and nonoperated sides. We used gross dissection and histologic sections to evaluate the degree of perineural fibrosis and walking-track analysis for neurologic evaluation.

RESULTS

Pre- and postoperative (30 minutes and 2 weeks) M- and D-SSEP were not statistically different. In group II, the relative amplitude of D-SSEP (elicited from 5 dermatomes) 1, 2, and 3 months postsurgery was lower; however, the M-SSEP in all groups and D-SSEP of groups I and III remained constant. Histologic evaluation of radiation efficacy showed that the frequency and extent of peridural fibrosis was consistently lower in group II than in group III.

CONCLUSION

Low-dose irradiation reduced peridural fibrosis and prevented fibrosis-induced radiculopathy. The radiation caused no adverse neuropathic complications.

Novel biomechanical quantification methodology for lumbar intraforaminal spinal nerve adhesion in a laminectomy and disc injury rat model

Spinal nerve fibrosis following injury or surgical intervention may play an important role in the pathophysiology of chronic back pain. In this current study, we demonstrate the role of biomechanical quantification of lumbar intraforaminal spinal nerve adhesion and tethering in the analysis of the post-laminectomy condition and describe a direct methodology to make this measurement. Twenty age-matched Sprague-Dawley male rats were divided into operative and non-operative (control) groups. Operative animals underwent a bilateral L5-L6 laminectomy with right-side L5-6 disc injury, a post-laminectomy pain model previously published by this lab. At eight weeks, animals were sacrificed and the strength of adhesion of the L5 intraforaminal spinal nerve to surrounding structures was quantified using a novel biomechanical methodology. Operative animals were found to have a significantly greater load to displace the intact right L5 spinal nerve through the intervertebral foramen when compared to control animals. The findings show that the post-laminectomy condition creates quantifiable fibrosis of the spinal nerve to surrounding structures and supports the conclusion that this fibrosis may play a role in the post-laminectomy pain syndrome.

A comparison of the effectiveness of mitomycin C and 5-fluorouracil in the prevention of peridural adhesion after laminectomy

Object

The effectiveness of the topical application of mitomycin C (MMC) or 5-fluorouracil (5FU) in preventing peridural adhesion after laminectomy was compared in this study.

Methods

Laminectomies were performed at L-1 in 30 rats. Cotton pads soaked with 0.1 mg/ml MMC, 25 mg/ml 5FU, or 9 mg/ml saline (control) were applied to the operative sites. To evaluate neurological deficits pre- and postoperatively, somatosensory evoked potentials were monitored and the Basso-Beattie-Bresnahan locomotion test was performed. Four weeks postlaminectomy the rats were killed, and peridural scar adhesion was evaluated histologically. The level of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts were determined. The degree of peridural adhesion was classified according to the Rydell standard.

Results

No obvious adhesion formed in the rats in the MMC group, but severe peridural adhesions were found in those in the 5FU and control groups. The content of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts in the MMC group were significantly lower than those in the 5FU and control groups.

Conclusions

The topical application of MMC rather than 5FU may be a successful method of preventing post-laminectomy peridural adhesions.