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

OBJECT: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

The effect of mitomycin C as fibrosis preventive agent during craniectomies.

OBJECT: The authors conducted a study to determine the effectiveness of mitomycin C (MMC) in preventing epidural fibrosis in rats which underwent craniectomy. METHODS: Craniectomies were performed in the right frontoparietal region; after the procedure the animals had been divided in 2 groups of 10 each. Cotton pads soaked with 0.1 mg/ml MMC or saline (control) were applied to the operative sites. Four weeks after craniectomy the rats were sacrificed, and epidural fibrosis was evaluated histologically. The dura mater thickness, the density of epidural fibrosis, arachnoidal involvement, and bone regeneration were determined. RESULTS: No obvious adhesion formed in the rats in the MMC group, but severe epidural adhesions were found in control group. The duramater thickness, the density of epidural fibrosis, and arachnoidal involved rat number in the MMC group were significantly lower than in control groups. CONCLUSIONS: Epidural fibrosis can be a devastating condition that forms after craniectomy. Topical application of mitomycin C may be a successful method of preventing epidural fibrosis following craniectomy.

Comparison of collagen biomatrix and omentum effectiveness on peripheral nerve regeneration.

Despite the presence of various nerve coaptation materials and techniques, achievement of the functional nerve regeneration is still inadequate. This study was aimed to compare the effectiveness of conduit composed of collagen biomatrix and omentum graft on peripheral nerve regeneration. Thirty-five male Wistar rats were divided into four groups. In the control group, the right sciatic nerve was skeletonized from the sciatic notch till the point of bifurcation. In the primary epineural repair group, the nerve was transected 1 cm proximal to the bifurcation with a sharp pair of micro scissors and then repaired with four epineural sutures. In the collagen biomatrix group, the epineural repaired nerve was wrapped with collagen biomatrix. In the collagen group, the epineural repaired nerve was wrapped with the nonpediculated omentum. Assessment of the nerve regeneration was based on functional (Walking Track Analysis, Electrophysiological Measurements), histological, and morphometric criteria. Light and electron microscopic examinations showed that collagen-biomatrix-wrapped specimens have the best regeneration. The electrophysiological study confirmed the recovery of electrical activity in the regenerated axons.

Morphometric characteristics of the inner and outer diameter of lumbar pedicles on computed tomography.

BACKGROUND AND PURPOSE: The inner pedicle diameter is very important in pedicle screw placement in order to achieve safe and strong posterior stabilization. The optimal pull-out strength can be achieved by a screw which fits into the pedicle medulla. The aim of the present study was to compare the inner and outer pedicle diameters of lumbar pedicles, to determine the inner/outer pedicle diameter ratios, and to develop a simple measure for estimating optimal pedicular screw size. MATERIAL AND METHODS: 178 lumbar pedicles of 20 patients were evaluated. Inner and outer pedicle diameters of lumbar vertebrae were measured in computed tomography (CT). A simple linear regression analysis was performed to assess the relationship between the inner and outer pedicle diameters. RESULTS: The widest pedicle outer diameter was seen at L5, with a mean of 16.538 +/- 1.899 mm. The narrowest pedicle outer diameter was seen at L1, with a mean of 8.310 +/- 1.870 mm. The maximum inner pedicle diameter was at the L5 level, with a mean of 11.416 +/- 2.664 mm, whereas the minimum was at the L1 level, with a mean of 5.510 +/- 1.887 mm. The regression coefficient between the inner and outer pedicle diameter was 0.68 for all pedicles combined. CONCLUSIONS: We have demonstrated the relation of the inner and outer pedicle diameter of lumbar pedicles and described an easy and reliable method to estimate the inner pedicle diameter from the outer diameter on CT.