Postlaminectomy scar formation in presence of epidural vicryl-collagenprostheses

J. Vaquero; A. Arias; S. Oya; M. ZuritaDepartment ofNeurosurgery, Puerta de Hierro Clinic, Autonomous University, and Department of Cell Bio1ogy, Complutense Univer­sity, Madrid, Spain.

Summary

An experimental study was performed in rats toevaluate the potential usefulness of the vicryl-collagenprosthesis in limiting epidural scar formation after la­minectomy. The results obtained suggest that the pre­sence of the prosthesis in the epidural space did notsignificantly influence the density or thickness of epi­dural scar tissue. Nevertheless, the fact that this mate­rial was well tolerated, being replaced by fibrous tissuewithout inflammatory tissular response, suggests thatits use in the epidural space may be preferable to thatof other absorbable materials and supports earlier stu­dies suggesting the usefulness of the vicryl mesh as adural substitute.

KEY WORDS: Vicryl, Epidural scar, laminectomy.

Resumen

Se presenta un estudio experimental sobre ratasadultas, diseñado para evaluar la potencial utilidad delas prótesis de vicril-colágeno para limitar la forma­ción de cicatrices epidurales tras la práctica de una la­minectomía. Los resultados obtenidos sugieren que lapresencia de este material en el espacio epidural raquí­deo no influye significativamente sobre la densidad o elgrosor de la cicatriz postoperatoria. Sin embargo, elhecho de que este material es bien tolerado, siendo sus­tituido por tejido fibroso, sin que se produzca una res­puesta inflamatoria, sugiere que su empleo sobre el es­pacio epidural puede ser ventajoso respecto de otrosmateriales bio-reabsorbibles y apoya los resultados deestudios previos que sugieren la utilidad de las mallasde vicril como sustitutos durales.

PALABRAS CLAVE: Vicril, cicatriz epidural, membranapostlaminectollÚa.

Introduction

It is a well-known fact that the development of scartissue over the epidural space following laminectomycomplicates the surgical technique when a second opera­tion is required in the same region. This problem arisesfrequentIy in lumbar disc surgery, where postoperativeepidural scarring has been postulated as a cause of recu­rrent symptomatology 2,3,6,8.

At present, diverse experimental studies have beenperforrned in the search for substances and materials capa­ble of limiting postlaminectomy epidural scarring 1,4,7-13,17.

Of these, grafts of autologous fat and rigid synthetic or he­terologous materials, such as methylmethacrylate or theKiel bone graft, to cover the laminectomy defect, appearto be effective in limiting postoperative adhesions 1,7,8,U,17.

Nevertheless, rigid materials can cause neural com­pression if not properly fitted to the laminectomy defectand generally remain as perrnanent foreing bodies withpersistent threat of infection. On the other hand, the effi­ciency of autologous fat grafts in preventing postoperativeepidural fibrosis has been questioned 14 and radicular com­pression caused by migration of the fat graft has recentlybeen reported 5. For these reasons, an effort should be ma­de to find a material which would limit postlaminectomyepidural scarring, which ideally should achieve this effectwithout remaining as a mass in the epidural region.

Recently, vicryl (polyglactin 910) mesh has been usedas a an absorbable dural substitute, and diverse studies ha­ve shown that this material is easy to handle and elicits aminimal inflarnmatory response 15,16. In addition, the expe­rimental use of vicryl mesh at laminectomy sites suggestsits potential usefulness in limiting postoperative epiduralscar forrnation 17.

In this report we present our experience with vicryl­coHagen prostheses introduced into rats in an attempt to li-·mit epidural scar forrnation foHowing laminectomy.

Material and methods

The vicryl-collagen prosthesis (Ethicon, Inc., Somervi­He, New Yersey) is an absorbable mesh of synthetic mate-

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Postlaminectomy scar formation in presence of epidural vicryl-collagen prostheses Neurocirugía

rial (polyglactin 910) coated with collagen of bovine ori­gin. In the present study, we used 21 adult Wistar rats,weighting 200 to 400 g. The animals were anesthetizedwith pentobarbital sodium (35 mg/Kg, intraperitoneally),after which they were fixed to the table in the prone posi­tion. A laminectomy was performed at D6-D8 level ineach animal, and the spinal cord, with its dura mater cove­ring, was exposed. After checking to see that the epiduralspace was not occupied by clots, the operative wound wasclosed in two layers by suturing paravertebral muscleswith 4/0 silk and stapling the skin. In 15 rats, prior to clo­sure of the wound, the laminectomy defect was coveredwith a sheet of vicryl-collagen. The remaining 6 animals,to which the prosthesis was not applied, were consideredas controls.

Groups composed of 7 animals (5 rats with epiduralprostheses and 2 controls) were sacrificed with intraperi­toneal lethal doses of pentobarbital sodium at 2, 4 and 8weeks after laminectomy.

Fig. 1- Rat with epidural prosthesis, two weeks after laminectomy. Anepidural fibrous tissue separating the spinal cord (SC) from the prost­hesis (V) can be seen. H.E. technique, original magnification x 50.

132

A block of the dorsal spine, including the larninectomyregion, was removed from each animal and fixed in 10%formaldehyde. Then, a decalcifying solution, Cal-Ex II(Fisher Scientific, Orangeburg, New York), was used todecalcify the specimens, which were transversally sliceduntil the larninectomy zone was disclosed. This zone wasembedded in paraffin for microscopical study with hema­toxylin-eosin, and van Gieson's techniques. At least tenhistological sections were studied from each animal and,in each section, the thickness and density of the scar overthe dura at the bone defect was assessed. This determina­tion was performed by two of the investigators, one ofwhom was not informed of the experimental techniqueused, and the findings were subjectively scored on a scaleof 1 to 4.

In this study, care of the animals complied with thatstipulated in the PrincipIes of Laboratory Animal Careand the Guidelines for the Care and Use of LaboratoryAnimals, published by the American National Society forMedical Research and the National Academy of Sciencesrespectively.

Results

Scar tíssue formatíon.Two weeks after surgery, the prosthesis was surroun­

ded by the epidural scar, and a fibrous tissue could be ob­served over the dura mater, separating it from the prosthe­sis (Figure 1). At four weeks, the scar was thicker and the­re was a wider separation between the prosthesis and thedura mater. At eight weeks, a thick, dense epidural scarwas found in all the animals studied. While this tissue was

Hg. 2- LeJi: mi Wil/z epidural pruslhesis, four weeks aJier laminec­tomy. At this time, a wider separation between the prosthesis (V) andthe spinal c.ord (SC) can be seen. Right: Control rat, four weeks afterlaminectomy. Significant difference in the thickness of epidural scarwas not found. H.E. technique, original magnification x 50.

Postlaminectorny scar formation in presence of epidural vicryl-coIlagenprostheses Neurocirugía

apparently less dense in sorne animals with prostheses, itwas not significantly different from that of controls whenthe mean score of the two groups were compared (Figures2 and 3).

cimen, and there was no evidence of inflammatory res­ponse or tissular alterations to indicate the previous pre­sence of the prosthesis.

Discussion

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Acknowledgement The authors thank Martha Messmanfor her expert editorial assistance.

Prior experiences with vicryl mesh as a dural substitu­te showed that this material was totally reabsorbed over aperiod of 40 to 60 days 15.16, and this finding has recentlybeen confmned with the use of vicryl mesh in spinal epi­durallocalization in dogs 17.

The results of this trial, with vicryl-collagen prosthesesplaced over spinal dura mater in rats, agree with the ear­lier observations. We also confirmed that the presence ofthis prosthetic material is associated with a minimal or ab­sent inflammatory tissular reaction 15.16,17.

Although we have been unable to confirm that thevicryl prosthesis is effective in significantly limiting epi­dural scar formation after larninectomy 17? the fact that itdoes not induce greater scarring than that observed in con­trols suggests that, when a dural reinforcement is conside­red, its use may be preferable to that of other materialssuch as gelfoam or avitene, which have been reported tocause greater scar formation when compared to controls 2,7,9.10. Furthermore, the fact that vicryl-collagen is well to­lerated and totally absorbed by the host, being replaced bya fibrous tissue, support its potential usefulness as a duralsubstitute, with properties similar to autologous fascia,and with advantages over other synthetic dural prostheseswhich remain as permanent foreign bodies and may causeclinical complications 15,16.

1. BARBERA, J., GONZALEZ, J., ESQUERDO, J., BROSETA, J.,BARCIA-SALaRIO, J.L.: Prophylaxis of the laminectomy membra­neo An experimental study in dogs. J. Neurosurg., 1978; 49: 419­424.

2. BENOIST, M., FICAT, C., BARAI, P., CAUCHOIS, J.: Postope­rative lumbar epiduroarachnoiditis. Diagnostic.and therapeuticaspects. Spine, 1980; 5: 432-436.

3. BRODSKY, A.E.: Post-Iaminectomy and post-fusion steno­sis of the lumbar spine. elin. Orthop., 1976; 115: 130-139.

4. BRYANT, M.S., BREMER, A.M, NGUYEN, T.Q.: Autogenicfat transplants in the epidural space in routine lumbar spine sur­gery. Neurosurgery, 1983; 13: 367-370.

5. CABEZUDO, J.M., LOPEZ, A., BACCI, F.: Symptomatic rootcompression by a free fat transplant after hemilaminectomy. J.Neurosurg., 1985; 63: 633-635.

References

This work was supported by a grant 92/0685 of theFIS.

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Vicryl-collagen reabsortion.Reabsortion of the prostheses could be clearly identi­

fied two weeks after surgery by the interlaced polyglactin­910 fibers (Figure 1). Collagen completely enveloped theprostheses, but the inflammatory reaction was minimal ornonexistent. At four weeks, the process of reabsortion wasclearly observed as the prosthesis was being replaced byfibrous tissue (Figure 4). Eight weeks after surgery,vicryl-collagen prostheses could not be found in any spe-

Fig. 4- Rat with epidural prosthesis, lour weeks ajier surgery. Leji: Alibrous epidural tissue, enveloping the prosthesis (V), can be seen.Right: At this time, the prosthesis (V) is being replaced by librous tis­sue without inflammatory tissular response. H.E. technique, originalmagni/ication x 50 (lelt) and x 125 (right).

Fig. 3- Graph bar showing the mean scores 01 thickness and density01 epidural scar tissue in the two experimental groups 01 rats.

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Postlanúnectomy scar formation in presence of epidural vicryl-collagen prostheses Neurocirugía

6. DEVll..LIERS, P.D., BOOYSEN, E.L.: Fibrous spina1 stenosis:A report on 850 mye10grams with a water-soluble eontrast me­dium. Clln. Orthop., 1976; 115: 140-144.

7. GILL, G.G., SAKOVICH, L., THOMPSON, E.: Pedie1e fatgrafts for the prevention of sear formation after 1amineetomy.An experimental study in dogs. Spine, 1979; 4: 176-186.

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9. KELLER, J.T., DUNSKER, S.B., MCWHORTER, J.M., ONGKI­KO, C.M., SAUNDERS, M.C., MAYFlELD, F.H.: The fate of auto10­gous grafts to the spina1 dura. An experimental study. J. Neuro­surg., 1978; 49: 412-418.

10. KIVll..UOTO, O.: Use of free fat transp1ants to prevent epi­dura1 sear formation. An experimental study. Acta Orthop.Seand. (Suppil), 1988; 164: 3-7:5.

11. LANGENSLIOLD, A., KIVll..UOTO, O.: Prevention of epidu­ra1 sear formation after operations on the lumbar spine by meansof free fat transplants. Clln. Orthop., 1976; 115: 92-95.

12. LA ROCCA, H., McNAB, 1.: The 1arnineetomy membrane.Studies in its evo1ution, characteristies, and prophy1axis in dogs.J. Bone Joint. Surg. (Br), 1974; 56B: 545-550.

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13. LEE, C.K., ALEXANDER, H.: Prevention of post1aminec­tomy sear formation. Spine, 1984; 9: 305-312.

14. MARTlN-FERRER, S.: Failure' of auto10gous fat grafts toprevent postoperative epidura1 fibrosis in surgery of the lumbarspine. Neurosurgery, 1989; 24: 718-721.

15. MAURER, P.K., McDoNALD, J.V.: Vicry1 (po1yg1actin 910)mesh as a dura! substitute. J. Neurosurg., 1985; 63: 448-452.

16. NUSSBAUM, C.E., MAURER, P.K., McDoNALD, J.V.:Vieryl (po1yg1aetin 910) mesh as a dural substitute in the pre­sence of pia araehnoid injury. J. Neurosurg., 1989; 71: 124­127.

17. NUSSBAUM, C.E., McDoNALD, J.V., BAGGS, R.B.: Use ofvicry1 (po1yglaetin 910) mesh to limit epidura1 sear formation af­ter 1arninectomy. Neurosurgery, 1990; 26: 649-654.

Vaquero, J.; Arias, A.; Oya, S.; Zurita, M.: Postlaminec­tomy scar formation in presence of epidura1 vicry1-colla­genprostheses. Neurocirugía 1992; 3: 131-134