Cranial Nerve Decompression Gasket

WANG Yun-yun(王云云)，LI Yu-ling(李毓陵) ，LI Shi-ting(李世亭)

1 College of Textiles，Donghua University，Shanghai 201620，China

2 Neurosurgery，Affiliated Xinhua Hospital，Medical College，Shanghai Jiao Tong University，Shanghai 200092，China

Introduction

The cranial nerve vascular compression syndrome refers to a series of cranial nerve dysfunction diseases that caused by vascular compression，inflammation，and other pathogenesis.The microvascular decompression (MVD)is the most widely therapeutic method used.The key is to implant a suitable decompression gasket between the corresponding vessels and nerve.The decompression gasket materials include gelatin sponge，polyester film，and Teflon cotton (PTFE).But those are easily absorbed or lack of systematic research［1-3］.The decompression gasket is a cotton-like fiber aggregation which must have the properties of biocompatible，non-toxic，nonallergenic，and irritant to fit biomedical.And it also requires softness， bulkiness， and elasticity to guarantee the decompression.

Accordingly，the impact of fiber fineness and crimp on the decompression gasket's physical properties was focused，and a comprehensive index system with the combination of subjective and objective evaluation was built.In addition， the biocompatibility of decompression gasket was analyzed with MTT assay.

1 Experimental

1.1 Materials

The PET multifilament used in this paper was bought from market，including 150D/36f， 150D/48f， and 150D/96f，having no crimp.

1.2 Preparation

The high crimp fiber was obtained by the knit-de-knit texturing method［4-5］.The multifilament was knitted into the weft knitting fabric;then the weft knitting fabric was cut into 1-cm-square small piece along vertical and horizontal orientations;finally，the fiber was taken out from the small piece to be made into a fiber aggregation(decompression gasket).The crimp degree of fiber was changed through varying weave densities.The weave densities of the decompression gasket samples are shown in Table 1.

Table 1 The weave densities of the samples

1.3 Characterization

Owing to the high ratio (250%-400%)of stretched length to natural length of the crimp fiber，its crimp properties were hard to be measured with the current instrument.The shape and dimension of each buckling wave on the textured fiber are essentially identical.Therefore，the buckling wave density and buckling wave perimeter were defined separately as the buckling wave number per cm along fiber natural length and the ratio of fiber stretched length to the buckling wave number，which were used to characterize the crimp properties［6］.

The physical properties of the decompression gasket include two aspects.The softness，which represents the degree of fiber to compress or excite a nerve，is characterized by the fiber diameter.And the decompression property，which means the ability of obstructing vascular compression，refers to the bulkiness and compress recovery ratio.The fiber diameter was tested by a reading microscope.The physical properties of the decompression gasket were performed on Tube Compression Elasticity Tester (LLY-06D)following the FZ/T50009.4-1998.

The MTT assay with neuronal cell of mouse (Shanghai Institutes for Biological Sciences，Chinese Academy)was used to test the cell proliferation rate (RGR)following the GB/T16886.5-2003.

2 Results and Discussion

2.1 Effects of fiber fineness and crimp on the physical properties

The fiber diameter and crimp degree of the samples are shown in Table 2.The bulkiness and compress recovery ratio of the samples are shown in Figs.1 and 2.It can be seen from Table 2，the softness increases with the decrease of fiber diameter.Figure 1 shows that the bulkiness has an upward trend with fiber fineness and the buckling wave perimeter depicts a downward trend.Also the compression recovery ratio does not have an obvious change trend in Fig.2.At equal mass，the fiber content and buckling wave quantity were found an inverse trend with fiber fineness and buckling wave perimeter，however，the fiber crimp elasticity and entanglement degree among fibers were in the same tendency.Therefore it is an interactive effect among the fiber diameter， buckling wave density， and perimeter.

Table 2 The fiber diameter and crimp degree of the samples

Fig.1 The bulkiness of the samples

Fig.2 The compress recovery ratio of the samples

2.2 Comprehensive evaluation of samples

In fact，the decompression effect of sample depends on patient treatment effect，but such tests have considerable difficulty，and the period is also very long.Therefore，all samples were tested by a finger-touch of the experienced clinician，and the clinician considered 8# sample was the best one.According to the result from clinician's subjective evaluation，the decompression effect of the decompression gasket should be regarded as an integrated physical property，which combines softness and decompression property.Therefore，the ratio of compress recovery ratio (E，%)to fiber diameter (D，mm)is used as the comprehensive index，which is defined as the comfort of the decompression gasket (M，mm-1).

The M value of the samples is shown in Fig.3，and the M value of 8# is the maximum.The subjective evaluation result is consistent with the objective evaluation result.The M value can be used as a method of the physical properties evaluation of the decompression gasket，and also as a basis for further biological experiments.

Fig.3 M value of the samples

2.3 Biocompatibility of materials

GB/T 16175-08 is referred to evaluating the cytotoxicity grade of samples.The relationship between the cell proliferation rate and cytotoxicity grade is shown in Table 3.The cytotoxicity results are shown in Table 4，and the cytotoxicity grade of materials is all at 1 level，and materials are non-cytotoxic and biocompatible.

Table 3 The relationship between cell proliferation rate and cytotoxicity grade

Table 4 The cytotoxicity results

3 Conclusions

The buckling wave density and buckling wave perimeter characterize the fiber crimp property; the softness is characterized by the fiber diameter;the characteristic indexes of decompression property include the bulkiness and compress recovery ratio.The compress recovery ratio of the decompression gasket has an upward trend with fiber diameter，however the softness and bulkiness increases with the decrease of fiber diameter.The value of M can be used to evaluate the physical properties of the decompression gasket.According to the MTT assay，all the tested samples were non-cytotoxic and biocompatible.

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