Inhibition of spinal fusion by use of a tissue ingrowth inhibitor

Efficacy of Poly(D,L-Lactic Acid-co-Glycolic acid)-Poly(Ethylene Glycol)-Poly(D,L-Lactic Acid-co-Glycolic Acid) Thermogel As a Barrier to Prevent Spinal Epidural Fibrosis in a Postlaminectomy Rat Model

STUDY DESIGN

Experimental animal study.

OBJECTIVE

The authors conducted a study to determine the efficacy and safety of the poly(D,L-lactic acid-co-glycolic acid)-poly(ethylene glycol)-poly(D,L-lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) thermogel to prevent peridural fibrosis in an adult rat laminectomy model.

SUMMARY OF BACKGROUND DATA

Peridural fibrosis often occurs after spinal laminectomy. It might cause persistent back and/or leg pain postoperatively and make a reoperation more difficult and dangerous. Various materials have been used to prevent epidural fibrosis, but only limited success has been achieved.

MATERIALS AND METHODS

The PLGA-PEG-PLGA thermogel was synthesized by us. Total L3 laminectomies were performed on 24 rats. The PLGA-PEG-PLGA thermogel or chitosan (CHS) gel (a positive control group) was applied to the operative sites in a blinded manner. In the control group, the L3 laminectomy was performed and the defect was irrigated with the NS solution 3 times. All the rats were killed 4 weeks after the surgery.

RESULTS

The cytotoxicity of this thermogel was evaluated in vitro and the result demonstrated that no evidence of cytotoxicity was observed. The extent of epidural fibrosis, the area of epidural fibrosis, and the density of the fibroblasts and blood vessel were evaluated histologically. There were statistical differences among the PLGA-PEG-PLGA thermogel or CHS gel group compared with the control group. Although there was no difference between the PLGA-PEG-PLGA thermogel and CHS gel, the efficiency of the PLGA-PEG-PLGA thermogel was shown to be slightly improved compared with the CHS gel.

CONCLUSIONS

The biocompatibility of the PLGA-PEG-PLGA thermogel was proven well. The application of this thermogel effectively reduced epidural scarring and prevented the subsequent adhesion to the dura mater. No side effects were noted in the rats.

Role of a collagen membrane in adhesion prevention strategy for complex spinal surgeries

PURPOSE

Following lumbar spine surgery, postoperative complications can appear, including epidural adhesions. The formation of fibrosis around the dura mater can, on the one hand, lead to compression of the nerve roots with recurrent radicular pain and, on the other hand, can increase the risks of specific complications at spinal re-intervention (haematomas and dural breaches). The aim of this prospective monocentric study was to assess the safety of a new collagen antiadhesion membrane in vertebral osteotomy surgery where scar tissue and adhesions are important.

METHODS

Twenty-six patients consecutively operated for lumbar posterior subtraction osteotomy with implantation of a collagen-based anti-adhesion membrane were evaluated. Membrane tolerance was evaluated at the short and midterm during the regular follow-up.

RESULTS

At six months' follow-up, postoperative pain [visual analogue scale (VAS)] and disability (Oswestry Disability Index score) were significantly reduced 33.1 and 43.1%, respectively. These results were confirmed at 12-months' follow-up, with a decrease in pain of 39.9% and in disability of 49.3%. Amongst the observed postoperative complications was neither spinal fluid leak nor durotomy. Presence of the membrane was not related to complications. Two patients required further surgery for infection and nonunion at the osteotomised level. Adhesions to the dura mater were limited and thin, facilitating exposure.

CONCLUSIONS

This study shows good tolerance of the collagen based membrane for spinal osteotomy and its satisfactory use for preventing postoperative epidural adhesions. Good surgical practice associated with an anti-adhesion barrier may decrease fibrosis formation and improve postoperative functional results.

The use of a dehydrated amnion/chorion membrane allograft in patients who subsequently undergo reexploration after posterior lumbar instrumentation

Background Context. Products that can reduce development of epidural fibrosis may reduce risk for ongoing pain associated with development of scar tissue and make subsequent epidural reexploration easier. Purpose. To evaluate the use of dehydrated human amnion/chorion membrane (dHACM) on the formation of soft tissue scarring in the epidural space. Study Design. Case series. Patient Sample. Five patients having transforaminal lumbar interbody lumbar fusion (TLIF) with posterior instrumentation and implantation of dHACM in the epidural space and subsequent epidural reexploration. Outcome Measures. Degree of scar tissue adjacent to the epidural space at reexploration. Intraoperative and postoperative complications related to dHACM and patient reported outcomes. Methods. The degree of scar tissue adjacent to the epidural space was assessed during the reexploration surgery. Patients' outcomes were collected using standard validated questionnaires. Results. Four of 5 cases had easily detachable tissue during epidural reexploration. Angiolipoma of 10% was noted in 1 case and 5% in 2 cases. Significant improvements in patient reported outcomes were observed. No intraoperative or postoperative complications occurred. Conclusions. Our findings suggest that dHACM implant during TLIF may have favorable effects on epidural fibrosis and is well tolerated. Further studies with larger cohorts are required to prove our results.

Adhesion prevention in an intraperitoneal wound model: performance of two resorbable hemostats in a controlled study in rabbits

Adhesions, particularly in the abdominal and pelvic cavities, represent a significant clinical problem. Among other complications, they are considered the most common cause of intestinal obstructions in the Western world. The purpose of this study was to evaluate two commercially available hemostats for their ability to prevent adhesion formation in an abdominal wound model. The hemostats, a microfibrillar collagen-based composite and microporous polysaccharide spheres were used in a rabbit abdominal model. In the model the cecum was abraded and a peritoneal defect was created on the abdominal sidewall. The test materials were applied over the defects. Clinical and histological results were compared with control (no application of any hemostat at the defect site) on postoperative day 14. The results showed a significant reduction in the incidence, extent and severity of adhesions for both surgical hemostat materials compared with control. The microfibrillar collagen-based composite showed a total absence of adhesions and a high level of reperitonealization. This preclinical study suggests that the use of surgical hemostats may help to reduce or eliminate adhesions and may promote reperitonealization.

One-stage posterior focus debridement, fusion, and instrumentation in the surgical treatment of cervicothoracic spinal tuberculosis with kyphosis in children: a preliminary report

PURPOSE

To determine the efficacy and feasibility of surgical management of cervicothoracic tuberculosis accompanied by kyphosis in children by using one-stage posterior focus debridement, bone graft fusion, and instrumentation at a single institution.

METHODS

Ten consecutive cases with cervicothoracic tuberculosis with kyphosis were treated with one-stage posterior focus debridement, bone graft fusion, and instrumentation. The mean follow-up was 36 months (range 26-47 months). The kyphotic angle ranged from 35° to 62° before operation, 50.5° in average. The American Spinal Injury Association score system was used to evaluate the neurological deficits.

RESULTS

Spinal tuberculosis was completely cured in all ten patients. There was no recurrent tuberculous infection. The postoperative kyphotic angle was 10° to 22°, 17.5° in average, and there was no significant loss of the correction at the latest follow-up. Solid fusion was achieved in all cases. Neurological condition in all patients was improved after surgery.

CONCLUSIONS

One-stage posterior debridement, bone grafting, and instrumentation can be an effective treatment method of cervicothoracic spinal tuberculosis with kyphosis in children.

Comparison of the immature sheep spine and the growing human spine: a spondylometric database for growth modulating research

STUDY DESIGN

A comparative study on growth of the sheep and human spine.

OBJECTIVE

To validate the immature sheep spine as model for the growing human spine and to yield a database for planning and interpretation of future animal experiments.

SUMMARY OF BACKGROUND DATA

With the current change of paradigm to nonfusion strategies for pediatric spine deformities, experimental surgery on spines of growing goats, sheep, and pigs has gained importance as preclinical proof-of-concept test. However, despite the proceeding use of animals, there is a lack of knowledge regarding the growth of the sheep spine and the relation to the human spine.

METHODS

Thoracic and lumbar cadaver spines were harvested from 50 Swiss alpine sheep. Specimens were obtained from newborn, 1, 3, 6, 9 and 12, 15 and 18 months old female sheep. Direct spondylometry yielded vertebral body heights, widths, and depths and spinal canal size, which were compared to pooled data on human spine growth retrieved from the literature.

RESULTS

Sheep spine growth ceases at age 15 to 18 months, which corresponds to a time-lapse model of human growth. Main growth occurs within the first 3 to 6 months of life, as opposed to human spines with maximal growth during the first 4 years and puberty. The relation between sheep and human vertebral shape is continuously changing with growth: at birth, sheep vertebrae are twice as tall, but equally wide and deep. At skeletal maturity, height is 15% to 25% bigger in sheep, but width 15% to 30% and depth 30% to 50% are smaller.

CONCLUSION

The immature sheep spine offers fast effects if growth-modulating interventions are performed within the first 3 to 6 months of age. The differences in vertebral shapes and further distinctions between human and sheep spines such as biomechanics, facet anatomy, and rib cage morphology have to be considered when interpreting results after experimental surgery.

Delayed Detected Unexpected Complication of ADCON-L® Gel in Lumbar Surgery

The ADCON-L gel® (Gliatech, Cleveland, OH, USA), a carbohydrate polymer gel, has been shown in a controlled clinical study to inhibit postsurgical adhesions and improve a patient's clinical outcome. Immediate complication of this gel has been reported in the recent literature including back pain, radiculitis and durotomy. However, delayed detection of disturbance of muscle healing and attachment in late postoperative state has been rarely reported. This report documents an unexpected delayed detected complication of the anti-adhesion barrier gel, which was used after lumbar discectomy one year ago, with review of literature.

Application of a new hydrogel dural sealant that reduces epidural adhesion formation: evaluation in a large animal laminectomy model

OBJECT

The aim of this study was to evaluate the application and effects of a novel, nonswelling, polyethylene glycol-based hydrogel adhesion barrier and sealant in a canine laminectomy model of CSF leakage and adhesion formation.

METHODS

After full-width L-2 and L-5 laminectomies, 1-cm midline durotomies were created and sutured closed, except for the last 1-2 mm on the cranial end to create spontaneous CSF leakage. All 5 control animals received no further treatment. Experimental animals received hydrogel at both durotomy sites via either the Dual Liquid applicator (5 animals) or MicroMyst gas-assisted sprayer (5 animals). Sealing of the CSF leak was confirmed by Valsalva maneuver. At 2 months, 2 animals from each group were killed to evaluate dural healing and epidural adhesion formation. The remaining animals were similarly evaluated 4 months after surgery. One animal died at 66 days due to a cause unrelated to hydrogel treatment.

RESULTS

In hydrogel-treated animals, all leaking durotomies were sealed intraoperatively. All animals recovered uneventfully. There were no treatment-related health effects. MicroMyst hydrogel application was more controlled, slower, and significantly less thick (p = 0.0094) than Dual Liquid application. All 5 control animals developed subcutaneous CSF accumulations under the incision within days of surgery, compared with only 1 of 10 hydrogel-treated animals (p = 0.002). At 2 and 4 months, control laminectomy sites showed extensive, dense epidural adhesions blending with neodura, compared with hydrogel-treated sites (p < 0.0001 and p = 0.0234, respectively). At 2 months in hydrogel-treated animals, gel filled the epidural space and no epidural adhesions were noted (p < 0.0001 relative to controls). At 4 months, the hydrogel was absorbed. The hydrogel space was filled with scant, loosely organized connective tissue.

CONCLUSIONS

Hydrogel prevented CSF leakage and mitigated epidural scarring without affecting healing of the dura or laminectomy site. The safety profile of the hydrogel appears favorable due to its synthetic composition, polyethylene glycol chemistry, minimal local tissue response, and lack of neurological deficits. Controlled application of such hydrogel materials may reduce the incidence of postoperative leaks, prevent adhesion formation and thus improve recovery from spinal surgery, and improve identification of tissue planes for reoperations.

Implantation of amniotic membrane to reduce postlaminectomy epidural adhesions

Postlaminectomy epidural adhesion is implicated as a main cause of "failed back surgery syndrome" and associated with increased risk of complications during revision surgery. Various materials acting as mechanical barriers to reduce fibroblasts infiltration into epidural space have met with limited success. In present research, amniotic membrane (AM) was studied to investigate its effects on reducing epidural scar adhesion after laminectomy in a canine model. Laminectomy sites were created at L-1, L-3, L-5, and L-7 levels in 24 adult mongrel dogs. Freeze dried AM (FAM), cross-linked AM (CAM), and autologous free fat (AFF) were implanted, respectively, at a randomly assigned site in each dog with the remaining untreated site serving as internal control. The animals were sacrificed at 1, 6, and 12 weeks postoperatively. Then, gross pathologic observation including scar amount and adhesion tenacity, qualitative histology evaluation, and quantitative histology analysis were compared. Gross observation demonstrated that scar amount and adhesion tenacity of CAM group were significantly lower in comparison with those of FAM and non-treatment groups. A white, slightly vascularized CAM layer covered the dura mater without tenacious scar adhesion. The histology analysis also indicated reduced fibroblasts infiltration and consequent epidural fibrosis, which were similar to the results of AFF group. In conclusion, the CAM is effective in reducing epidural fibrosis and scar adhesion after laminectomy in canine model. It is a promising biomaterial for future clinical applications.

Platelet-rich plasma inhibits demineralized bone matrix-induced bone formation in nude mice

BACKGROUND

It is unclear whether platelet-rich plasma is a clinically effective adjunct to osteoinductive agents such as demineralized bone matrix. It contains platelet-derived growth factor (PDGF), which decreases osteoinduction by human demineralized bone matrix in nude-mouse muscle, suggesting that platelet-rich plasma may also have a negative impact. This study tested the hypothesis that platelet-rich plasma reduces demineralized bone matrix-induced bone formation and that this effect varies with donor-dependent differences in platelet-rich plasma and demineralized bone matrix.

METHODS

Human platelet-rich plasma was prepared from blood from six men (average age [and standard error of the mean], 29.2 +/- 2.4 years). Platelet numbers were determined, and growth factors were quantified before and after platelet activation. Human demineralized bone matrix from two donors (demineralized bone matrix-1 and demineralized bone matrix-2) was mixed with activated platelet-rich plasma and was implanted bilaterally in the gastrocnemius muscle in eighty male nude mice (eight implants per variable). Fifty-six days after implantation, the hindlimb calf muscles were harvested for histological analysis. Osteoinduction was evaluated with use of a qualitative score and morphometric measurements of ossicle size, new bone formation, and residual demineralized bone matrix.

RESULTS

Compared with platelet-poor plasma, platelet-rich plasma preparations exhibited a fourfold increase in the platelet count, a fifteenfold increase in the amount of transforming growth factor-beta, a sixfold increase in the amount of PDGF-BB, a fivefold increase in the amount of PDGF-AA, and a twofold increase in the amount of PDGF-AB. Demineralized bone matrix-1 was more osteoinductive than demineralized bone matrix-2, as determined on the basis of a greater ossicle area. The effect of platelet-rich plasma was either neutral or inhibitory depending on the demineralized bone matrix batch. When used with demineralized bone matrix-1, platelet-rich plasma did not alter the qualitative score or overall ossicle size, but it decreased the new bone area. When used with demineralized bone matrix-2, platelet-rich plasma reduced the qualitative score, ossicle area, and new bone area and increased the amount of residual demineralized bone matrix. The effects on osteoinduction also varied with the donor of the platelet-rich plasma.

CONCLUSIONS

Platelet-rich plasma decreased the osteoinductivity of demineralized bone matrix implanted in immunocom-promised mice, and the activities of both demineralized bone matrix and platelet-rich plasma were donor-dependent.