Use of polylactide resorbable film as an adhesion barrier

Protective effect of biodegradable nerve conduit against peripheral nerve adhesion after neurolysis

OBJECTIVE Peripheral nerve adhesion caused by extraneural and intraneural scar formation after neurolysis leads to nerve dysfunction. The authors previously developed a novel very flexible biodegradable nerve conduit composed of poly(L-lactide) and poly(ε-caprolactone) for use in peripheral nerve regeneration. In the present study, they investigated the effect of protective nerve wrapping on preventing adhesion in a rat sciatic nerve adhesion model. METHODS Rat sciatic nerves were randomly assigned to one of the following four groups: a no-adhesion group, which involved neurolysis alone without an adhesion procedure; an adhesion group, in which the adhesion procedure was performed after neurolysis, but no treatment was subsequently administered; a nerve wrap group, in which the adhesion procedure was performed after neurolysis and protective nerve wrapping was then performed with the nerve conduit; and a hyaluronic acid (HA) group, in which the adhesion procedure was performed after neurolysis and nerve wrapping was then performed with a 1% sodium HA viscous solution. Six weeks postoperatively, the authors evaluated the extent of scar formation using adhesion scores and biomechanical and histological examinations and assessed nerve function with electrophysiological examination and gastrocnemius muscle weight measurement. RESULTS In the adhesion group, prominent scar tissue surrounded the nerve and strongly adhered to the nerve biomechanically and histologically. The motor nerve conduction velocity and gastrocnemius muscle weight were the lowest in this group. Conversely, the adhesion scores were significantly lower, motor nerve conduction velocity was significantly higher, and gastrocnemius muscle weight was significantly higher in the nerve wrap group than in the adhesion group. Additionally, the biomechanical breaking strength was significantly lower in the nerve wrap group than in the adhesion group and HA group. The morphological properties of axons in the nerve wrap group were preserved. Intraneural macrophage invasion, as assessed by the number of CD68- and CCR7-positive cells, was less severe in the nerve wrap group than in the adhesion group. CONCLUSIONS The nerve conduit prevented post-neurolysis peripheral nerves from developing adhesion and allowed them to maintain their nerve function because it effectively blocked scarring and prevented adhesion-related damage in the peripheral nerves.

Antiadhesive effect of bioresorbable polylactide film in abraded middle ear mucosa

BACKGROUND AND OBJECTIVE

Polylactide film (PLF) is used to prevent postoperative peridural adhesion in spinal surgery. Up until now, the antiadhesive effect of bioresorbable PLF in ear middle surgery has not been reported. The purpose of this study is to evaluate the antiadhesive effect of PLF in guinea pigs serving as a model for middle ear mucosal trauma.

MATERIALS AND METHODS

The animals were divided into two groups: the PLF group and the silastic sheeting group. There were seven guinea pigs (fourteen ears) in both groups. Under aseptic conditions, the middle ear mucosa was abraded using a pick inserted transbullaly. A PLF or silicone sheet was then placed into the guinea pigs' middle ear cavities. The auditory brainstem responses (ABRs) were assessed preoperatively and at three weeks postoperatively while the animals were under general anesthesia. A histopathological study was performed 3 weeks after the operation.

RESULTS

The difference between the ABR results before the operation and three weeks postoperatively were not statistically significant. The adhesion formation did not appeared in either group. Prominent fibrous capsule formation and inflammation were observed in the silastic sheeting group, but not in the PLF group. Mild fibrous thickening of regenerated mucosa was observed in the PLF group.

CONCLUSION

From our results, bioresorbable PLF is nonototoxic and biocompatible with the guinea pig's middle ear cavity by short-term evaluation. Further long-term evaluation study is necessary before clinical application.

Techniques and materials for enhancement of peripheral nerve regeneration: a literature review

Peripheral nerve surgery performed under unfavorable conditions results in increased scar formation and suboptimal clinical outcomes. Providing the operated nerve with a protective barrier, reduces fibrosis and adhesion formation and may lead to improved outcomes. The ideal coverage material should prevent scar and adhesion formation, and maintain nerve gliding during motion. Nerve protection using autologous tissues has shown good results, but shortcomings include donor site morbidity and limited availability. Various types of methods and materials have been used to protect nerves. There are both advantages and disadvantages associated with the various materials and techniques. In this report we summarize currently used protective materials applied for nerve coverage under various surgical conditions.

Comparison of a caprolactone/lactide film (mesofol) to two polylactide film products as a barrier to postoperative peridural adhesion in an ovine dorsal laminectomy model

STUDY DESIGN

Experimental study.

OBJECTIVE

To evaluate and compare the performances of 2 bioresorbable products, Mesofol (a caprolactone/lactide film) and Lactosorb (a polylactide film), as barriers to postoperative peridural adhesions and fibrosis.

SUMMARY OF BACKGROUND DATA

Postoperative peridural adhesions from scar tissue may be an inciting cause of chronic pain and dysfunction in "failed back" syndrome. Many biocompatible products and drugs, as well as autografts have been tested as antiadhesion barriers with varying success.

METHODS

The bioresorbable film products were used to cover large laminectomy defects in 11 sheep. Three laminectomy defects were created, with 2 randomly assigned treatment sites and 1 control site in each animal. A tear was created in the dura allowing cerebrospinal fluid leakage to assess for impaired dural healing. Performance of the film barriers was assessed at 10 weeks postoperative by gross scar and tenacity scoring by 3 blinded, independent observers in 7 animals. Histology was performed in 4 animals. New Methylene blue dye myelography and magnetic resonance imaging were performed to assess for cerebrospinal fluid leakage. Magnetic resonance imaging was also used to evaluate the imaging characteristics of adhesions.

RESULTS

All 3 products evaluated showed a benefit to prevention of postoperative peridural adhesion; the performance of Mesofol was deemed superior to either of the 2 Lactosorb products. The handling characteristics of all products were compatible with clinical usage. Impairment to healing of dural tears or active inflammation was not identified with any product.

CONCLUSION

The results of this investigation support previous studies on the benefit of polylactide film barriers, like Lactosorb, for reducing peridural adhesion following spinal surgery. The performance of Mesofol in this investigation suggests that it may provide improved antiadhesion properties in comparison to the polylactide products. Safety issues related to impaired dural healing was not identified in either product.

Long-term magnetic resonance imaging evaluation of bioresorbable anterior cervical plate resorption following fusion for degenerative and traumatic disk disruption

STUDY DESIGN

A retrospective magnetic resonance imaging (MRI) review of a series of patients who underwent a single-level anterior cervical discectomy and fusion followed by anterior plate stabilization using an anterior cervical resorbable mesh plate and screw system.

OBJECTIVE

MRI evaluation of the long-term implant resorption properties of a bioresorbable anterior cervical plate and the adjacent peri-implant soft tissue environment.

SUMMARY OF BACKGROUND DATA

The use of bioresorbable anterior cervical plates for immediate cervical stabilization following an anterior cervical discectomy and fusion presents several distinct advantages over metallic instrumentation. Bioresorbable polymers may diminish, by their resorbability, implant-related complications such as loosening, migration, and failure of instrumentation, as well as stress shielding of the underlying fusion. Information on the intermediate and long-term bony and soft tissue reaction to the resorption byproducts of these biomaterials is limited.

METHODS

There were 9 consecutive patients who underwent single-level anterior cervical decompression and fusion using allograft cortical bone, followed by bioresorbable polylactide anterior mesh plate and screw fixation. Following institutional review board approval, 5 of the 9 patients agreed to postoperative MRI assessment of the peri-implant area. An independent radiologist then characterized implant degradation, and the presence of soft tissue inflammation and swelling during the resorption phase of the bioresorbable plate.

RESULTS

At an average follow-up of 32 months, MRI assessment showed no evidence of soft tissue swelling or inflammation related to the resorption of a bioresorbable anterior plate in any of the 5 patients. In addition, none of the patients complained of any dysphagia or phonation difficulties.

CONCLUSIONS

Based on MRI assessment, these devices, at more than 2-year follow-up, did not indicate any local chronic inflammation or swelling resulting from their degradation. Clinical symptoms of dysphagia or dysarthria, a common reported problem following anterior cervical spine procedures, were not observed in any patient.

Cervical spine fusion with bioabsorbable cages

Object

Although it improves rates of fusion in surgical arthrodesis, conventional spinal instrumentation is associated with several risks, including hardware extrusion that injures adjacent anatomical structures, and disuse osteopenia as a result of stress shielding. The long-term effects of indwelling spinal instrumentation, although incompletely documented, may be detrimental. One way to avoid such problems would be to use bioabsorbable implantation devices. In this pilot study, performed in 1998 and 1999, the authors evaluated the use of a bioabsorbable interbody fusion device in a goat cervical spine model.

Methods

Forty-two goats underwent two-level anterior cervical discectomy and fusion: eight received iliac crest autograft; 16 received a cage implant composed of 70:30 poly(L-lactide-co-D,L-lactide)/polyglycolic acid (70:30 PLDLLA/PGA) filled with either autograft or recombinant human bone morphogenetic protein–2 (rhBMP-2); and 18 received a cage implant composed of 85:15 PLDLLA/PGA filled with either autograft or rhBMP-2. Animals were killed at 3, 6, and 12 months postsurgery, and their cervical spines were evaluated histologically, radiographically, and physically for fusion.

A primarily fibrous union was demonstrated in all animals killed at 3 months. At 6 months, bone trabeculae had become more prominent and the fibrous response less so in all cohorts. This occurred most frequently in the animals that underwent fusion with the 70:30 PLDLLA/PGA cages filled with rhBMP-2, in which 63% attained a histologically confirmed union that contained quantitatively more bone and less fibrous tissue than in the other cohorts; 63% of the unions in the aforementioned cohort were graded quantitatively as being stable.

Conclusions

In this study the authors have established that the 85:15 PLDLLA/PGA cages are absorbed too quickly to be functionally useful in this model. The 70:30 PLDLLA/PGA cages worked as well as tricortical autograft when filled with cancellous autograft, and better when filled with rhBMP-2. At 6- and 12-month follow-up review, the 70:30 PLDLLA/PGA cages had not yet begun to be absorbed. There was little if any inflammatory response to these cages at 6 months. Future studies should include biomechanical and microradiographic testing, and a longer follow-up period is necessary in this model to determine when the 70:30 PLDLLA/PGA cages are absorbed.

The use of bioabsorbable implants in spine surgery

The use of bioabsorbable implants in spine surgery is expanding at a rapid pace. These implants are mimicking the roles of traditional metallic devices and are demonstrating similar efficacy in terms of maintaining stability and acting as carriers for grafting substances. Biomechanical studies have demonstrated their ability to stabilize effectively a degenerative cervical and lumbar motion segment. In numerous animal models, researchers have illustrated the ability of bioabsorbable implants to function satisfactorily as an interbody spacer and to achieve satisfactory bone fusion. Investigators have explored various opportunities for these implants to replace their metallic counterparts in clinical studies conducted in humans. The gradual resorption of these implants appears effectively to transfer gradual loads to the grafting substances promoting the biological mechanisms of fusion.

Novel uses of bioabsorbable technology are constantly evolving. Their future as a carrier of biological agents such as bone morphogenetic proteins and bone graft extenders, their radiolucency, and their eventual resorption make them an ideal implant for use in spinal degenerative disease.

Use of polylactide resorbable film as a barrier to postoperative peridural adhesion in an ovine dorsal laminectomy model

Object

The purpose of this study was to evaluate the performance of a resorbable polylactide film in the sheep posterior spine in the presence of a combined laminectomy and durotomy defect.

Methods

A resorbable polylactide film was used to cover the combined defects in the eight sheep used in this study. Two surgical levels were performed in each animal, with randomly assigned control and treated sites. Each surgical level consisted of a full laminectomy followed by a needle-induced durotomy. The treated levels received a resorbable polylactide film cut to size and tucked in under the laminar defect. At 8 to 10 weeks postoperatively, results of myelography and visual dye infiltration showed complete healing of the durotomies for all sites. In addition, evaluation of gross dissection based on volume and tenacity scores as well as histological findings indicates decreased posterior dural adhesions for sites treated with resorbable polylactide film.

Conclusions

The results of this investigation support previous studies in which the use of a resorbable polylactide film was found to be effective in reducing posterior dural adhesions in the spine with no apparent safety issues related to impaired dural healing.