CT advantages of potential use of polymer plastic clips in neurocranium.

Aim Clips in neurosurgery are made of titanium alloys, which reduce artifacts on computed tomography (CT). The radiological advantage of plastic clips on the CT image was demonstrated when they were placed in an inter-hemispherical position at an angle of 90º. The aim of this study was to investigate the behaviour of the clip placed at different angles. Methods Sixty heads of domestic pigs were divided into two groups, in group 1 a titanium clip was placed to the interhemispheric position at an angle of 90º, 45º, 0º, ten heads for each angle. In group 2 a plastic clip was placed in the same way. CT scan of the brain was performed for each angle. The size of the density and possible artifact were measured on CT. Results The size of the titanium clip ranged from 17.05 mm at an angle of 0º in the axial plane to 91.47 mm at an angle of 0º in the sagittal plane. The average size of the plastic clip ranged from 6.4 mm at an angle of 0º in the axial plane to 23.22 mm in an angle of 90º in the sagittal plane. Artifacts were observed only in the titanium clip. Conclusion Plastic clips have shown radiological advantages over titanium clips in the CT image. The average density size of the plastic clip in all planes and all angles was smaller than the titanium clip.

Morphological Changes in Blood Cells After Implantation of Titanium and Plastic Clips in the Neurocranium - Experimental Study on Dogs.

INTRODUCTION: Various studies confirm the biocompatibility and efficacy of clips for certain target tissues, but without any comparative analysis of hematological parameters. Therefore, we conducted a study to assess the possible association of the implantation of titanium and plastic clips in the neurocranium with possible morphological changes in the blood cells of experimental animals. MATERIALS AND METHODS: As a control, the peripheral blood smears were taken before surgery from 12 adult dogs that were divided into two experimental groups. After placing titanium and plastic clips in the neurocranium, the peripheral blood of the first group was analyzed on the seventh postoperative day, while the peripheral blood of the second group was analyzed on the sixtieth day. By microscopy of the blood smears, the following parameters were analyzed: the presence of poikilocytosis of the red blood cells, degenerative changes in the leukocytes and leukogram. RESULTS: There were no statistically significant differences between the mean values of the groups. Monocytosis was detected (first group 22.83 % and second 16.30 %), as well as neutropenia (46.80 %, in the second group). Degenerative changes to neutrophils and the occurrence of atypical lymphocytes were observed in the second experimental group (60th postoperative day). CONCLUSION: A mild adverse effect from the biomaterials present in the neurocranium of dogs was detected, affecting the majority of leukocytic cells. A chronic recurrent inflammatory process was caused by the presence of the plastic and titanium clips in the brain tissue. No adverse effect of biomaterials on erythrocytes in the neurocranium was detected in the dogs studied. Further studies are necessary to explain the occurrence of degenerative changes in the neutrophils and lymphocytes.

Intensity of the stimulating current may not be a reliable indicator of intraneural needle placement.

BACKGROUND AND OBJECTIVES: The current intensity at which a motor response is elicited with an intraneural needle placement has been inadequately studied. We hypothesized that electrical current delivered through an intraneurally placed needle does not always result in an evoked motor response. Our secondary objective was to determine the relationship between electrical current intensity and needle-to-nerve distance. METHODS: Twenty pigs were given general anesthesia and the sciatic nerves (SN) were exposed bilaterally. Electrical nerve stimulation was applied 2 cm, 1cm, 0.5 cm, 0.2 cm, and 0.1cm away from the SN, transepineurally, and intraneurally (in the subepineurium). Stimulation was started at 2.0 mA and decreased to the minimal current at which visible motor response was obtained. Two blinded observers agreed on the intensity and type of motor response. Specific response of SN was defined as a distal motor response (hoof twitch); nonspecific response was defined as a local muscle twitch (no hoof response). RESULTS: At a distance of 0.5 cm to 2 cm away from the SN, only nonspecific muscle responses were observed. Specific SN responses were obtained starting at 0.1 cm away from the nerve and transepineurally with currents of 0.92 +/- 0.33 mA (median 1.00 mA; range 0.24-1.48 mA) and 0.39 +/- 0.33 mA (median 0.3 mA; range 0.15-1.4 mA), respectively. With the needle tip positioned intraneurally, specific motor response could be obtained at 0.56 +/- 0.54 mA (median 0.3 mA; range 0.08-1.80 mA). Five (12.5%) intraneurally positioned needles only elicited a specific motor response at 0.8-1.8 mA. CONCLUSIONS: Specific response to nerve stimulation with currents <0.2 mA occurred only when the needle tip was positioned intraneurally. However, motor response could be absent with intraneural needle placement at a current intensity of up to 1.7 mA.