3.1 Animal model establishment and typical F-wave waveform
Thirty New Zealand white rabbits were used in this experiment. Two rabbits were excluded due to lumbar artery variation or intraoperative bleeding. The remaining rabbits successfully underwent the surgical procedure and post-operative evaluation process. After anaesthesia, the rabbits were free to eat. The success rate of the animal models was 93.3%. After anaesthesia, all animals obtained ideal waveforms in this group. The latency of the F-wave of all 30 rabbits before ligation was 11.2±1.4 ms and the amplitude was 790.3±589.5 μV.
3.2 The control group
Analysis of Variance of a Single Set of Repeated Measurement Data was used to analyse, after anaesthesia, the amplitude of the control group at different times. The spherical test results were χ2 = 34.634, P<0.05. The data did not meet the Huynh-Feldt condition or satisfy the spherical hypothesis. There was no statistically significant difference in the corrected variance analysis results (F = 0.59, P>0.05). Analysis of Variance of a Single Set of Repeated Measurement Data was used to analyse, after anaesthesia, the latency of the control group at different times. The spherical test results were χ2 = 30.761, P<0.05. The data did not meet the Huynh-Feldt condition or satisfy the spherical hypothesis. There was no statistically significant difference in the corrected variance analysis results (F = 1.738, P>0.05). Analysis of Variance of a Single Set of Repeated Measurement Data was used to analyse the amplitude of the different times before and after the operation in the control group. The results of the spherical test were χ2 = 6.071,P>0.05. The data satisfied the spherical assumptions, and no freedom correction was required. There was no statistically significant difference (F = 1.212, P>0.05). Analysis of Variance of a Single Set of Repeated Measurement Data was used to analyse the latency of the different times before and after the operation in the control group. The results of the spherical test were χ2 = 6.727, P <0.05. The data did not meet the Huynh-Feldt condition, and the spherical hypothesis was not satisfied. There was no statistically significant difference in the corrected variance analysis results (F = 3.969, P> 0.05). Therefore, the changes in the F-wave during the course of the experiment were not related to anaesthesia and surgery.
3.3 Experimental group
No waveform changes in the F-waves were found after ligation in group 1 and group 2.The waveform of the F-wave began to change rapidly after lumbar artery ligation in group 3, group 4, and group 5. The latency began to increase and the amplitude to decrease immediately. The waveforms began to decrease after 0.9 ± 0.3 min, 0.7 ± 0.3 min, and 0.8 ± 0.2 min, respectively, in group 3, group 4, and group 5. Then, they started to stabilize after 1.3 ± 0.3 min, 1.9 ± 1.6 min, and 1.9 ± 0.5 min, respectively, in group 3, group 4, and group 5(Fig ure1).
3.3.1 Amplitude changes
In the experimental group, the amplitude change can be recorded to be consistent with the damage degree after spinal cord ischaemia. The F-wave amplitude disappeared in group 5 after lumbar artery ligation. There was no statistically significant difference according to the amplitude paired t-test after lumbar artery ligation when the F-wave was steady compared to before the operation in group 1 and group 2 (all P> 0.05). There was a statistically significant difference according to the amplitude paired t-test after lumbar artery ligation when the F-wave was steady compared to before the operation in group 3, group 4, and group 5 (all P<0.05) (Table 1).
group before surgery(%) after surgery(%) P t
Group1 100.0±0.0 100.6±1.6 0.512 0.741
Group2 100.0±0.0 98.1±2.8 0.209 1.495
Group3 100.0±0.0 78.1±9.0 a 0.005 5.472
Group4 100.0±0.0 33.5±16.6 a 0.001 8.941
Group5 100.0±0.0 0±0 / /
|
a, paired t-test after and before lumbar artery ligation, P<0.05.
|
Table 1
The percentage values of the F-wave amplitude after ligation and the baseline before ligation at different times (`x±s)
3.3.2 Latency changes
There was no statistically significant difference according to the latency paired t-test after lumbar artery ligation when the F-wave was steady compared to before the operation in group 1 and group 2 (all P> 0.05). The latency of the F-wave began to extend rapidly in group 3, group 4, and group 5. There was a statistically significant difference according to the paired t-test in the latency after lumbar artery ligation when the F-wave was steady compared to before the operation in group 3 and group 4 (all P<0.05) (Table 2)
group before surgery (ms) latency after surgery (ms) P t
Group1 11.0±1.7 11.0±1.7 0.215 1.567
Group2 11.1±1.4 11.2±1.5 0.099 2.138
Group3 12.1±1.7 12.8±2.0 a 0.03 3.283
Group4 11.4±1.5 13.7 ±1.4 a 0.001 8.061
Group5 11.2±1.3 / / /
|
a, paired t-test after and before lumbar artery ligation, P<0.05.
|
Table 2
F-wave latency after and before ligation at different times (`x±s)
3.4 Histomorphological observation of lumbar spinal cord pathological sections.
Normal spinal cord tissue with complete structure and neuronal cells with normal morphology in the control group, group 1 and group 2 could be seen under the light microscope. The spinal cord structure was basically complete in group 3. Point foci degeneration, necrosis, and mild edema of the grey matter could be seen under the light microscope. We could see many morphologically normal neurons. Several neurons became smaller, and the cytoplasm became concentrated. The density of the nuclear chromatin increased, showing apoptotic changes. The spinal cord structure basically disappeared in group 5, with obvious congestion and swelling. There were a large number of vacuolar degenerations and a small number of normal neurons. The nuclei of most neurons were atrophic or dissolved; the cytoplasm was eosinophilic; and the Nissl bodies in the cytoplasm disappeared(Figure 2). The experimental results in group 4 was between those in group 3 and group 5.
3.5 Results of spinal motor function scores
There was no statistically significant difference in motor function score 2 days after ligation according to the two independent samples Wilcoxon rank sum test between the control group and group 1, group 2, and group 3 (all P> 0.05). There was no statistically significant difference in motor function score according to the paired-sample Wilcoxon rank sum test between before and 2 days after ligation in group 1, group 2, and group 3(all P> 0.05). There were statistically significant differences in motor function score 2 days after ligation according to the two independent samples Wilcoxon rank sum test between the control group and groups 4 and 5 (Z = 2.835 and Z = 2.739, all P<0.05). There were statistically significant differences in motor function score according to the paired-sample Wilcoxon rank sum test before and 2 days after ligation in group 4 and group 5(Z = 2.07 and Z = 2.126, all P<0.05) (Table 3).
group before surgery after surgery 2d
Control group 5.0(5.0,5.0) 5.0(5.0,5.0)
Group 1 5.0(5.0,5.0) 5.0(5.0,5.0)
Group 2 5.0(5.0,5.0) 5.0(5.0,5.0)
Group 3 5.0(5.0,5.0) 5.0(5.0,5.0)
Group 4 5.0(5.0,5.0) 4.0(2.0,5.0)a b
Group 5 5.0(5.0,5.0) 0.0(0.0,0.8)a b
|
a, the two independent samples Wilcoxon rank sum test compared with the control group, P<0.05. b, the paired-sample Wilcoxon rank sum test before and 2 days after ligation, P<0.05.
|
Table 3
Motor function score (score) M(QL, QU)
3.6 Correlation analysis
Based on the Pearson’s relation analysis, the percentage value of the F-wave amplitude when the F-wave was steady after ligation and the baseline before ligation was positively correlated with the motor functions (r = 0.964). There was a statistically significant difference (P<0.01).