| BackgroundOssification of posterior longitudinal ligament(OPLL)is a multifactorial disease caused by ectopic bone hypertrophy and posterior longitudinal ligament calcification.Its ossifications continue to grow and eventually compress the spinal cord and/or nerve roots,resulting in limb sensation and movement disorders.The condition of thoracic OPLL is complicated and can only be treated surgically,but the previous surgical method is difficult and has many complications.As a new surgical method,thoracic column antedisplacement and fixation(TCAF)achieves direct decompression of the spinal cord while avoiding direct removal of ossification,which greatly reduces the difficulty of the operation and the risk of complications.However,the technology is still being improved,the operation process is cumbersome,the operation time is long,and the real-time monitoring of somatosensory evoked potential(SSEP)is required during the operation.However,the penetration rate of TCAF is not high,and there are few related theoretical studies.Is the antedisplacemental distance an effective and reliable quantitative reference index?Is there a correlation and linear relationship between the limit distance and the related parameters of the antedisplacemental vertebral body?How about the three-dimensional stability of the antedisplacemental complex?These issues are worth investigating.ObjectivesThrough goat animal experiments to clarify the feasibility of TCAF technology in goat animals,and explore whether the antedisplacemental distance has an effective and reliable quantitative reference index;whether there is a correlation and linear relationship between the antedisplacemental distance and the related parameters of the antedisplacemental vertebral body.Biomechanics experiments to explore the three-dimensional stability of the antedisplacemental complex and the optimal number of fixed screw groups for the antedisplacemental complex.Methods1.To explore the safety of the spinal cord by TCAF surgery.Ten healthy adult goats were selected as animal experiments.The T12-13 and L1 are selected as the antedispalcemental vertebral while T10-11 and L2-3 are chosen as fixed vertebral.The TCAF operation was performed under SSEP monitoring by using pedicle screw system to push the vertebral forward according to the adjustment of the length of the reserved thread until the SSEP just did not showed a positive result,at which time the length of the reserved thread was recorded,and the distance of the antedisplacemental distance measured by postoperative imaging was the ultimate antedisplacemental distance.Explore whether there is a correlation and linear relationship between the ultimate antedisplacemental distance and the related parameters of the vertebral body.According to the function of the spinal cord 2 days after the operation,the impact of the TCAF operation on the safety of the spinal cord was evaluated again.2.Biomechanical study of postoperative goat spine specimens.The spinal specimens of normal and postoperative goats were collected and divided into 4 groups(8 in each group)according to the number of groups of adjusting fixation screws.Group 1:one set of the fixation screws upper and lower;Group 2:two set of the fixation screws upper and lower.Group 3:three set of the fixation screws upper and lower.Group 4:blank control group.Three-dimensional stability was measured in turn.Results1.In TCAF surgery,the ultimate antedisplacemental distance is 8.0±0.2mm,and Pearson correlation test shows that there is a good correlation with the average anteroposterior diameter of the antedisplacemental segment and the average width of the vertebral bodies of the antedisplacemental segment.Linear regression analysis showed that there was a linear relationship between the ultimate antedisplacemental distance and the average anteroposterior diameter of the antedisplacemental segment spinal canal.2.The three-dimensional stability of goat spine specimens was measured and the ROM values between each status group were analyzed by Independent-Sample T Test.It was found that the ROM values of the spine specimens of the antedisplacemental complex were significantly decreased under 6 motion states,and the difference was statistically significant compared with that of normal spine specimens(P<0.05).The spinal specimens of the antedisplacemental complex were stable in each motion state,and the internal fixation device could provide a firm fixation effect.The overall stability of the antedisplacemental complex was good.The ROM values of each experimental group were compared by one-way analysis of variance(ANOVA)and the least significant difference t-test(LSD-T).The ROM values of the second group were lower than that of the first group,and the difference was statistically significant(P<0.05).There was no significant difference in ROM values between group 2 and group 3(P>0.05).It is indicated that the optimal number of fixation screw groups for the antedisplacemental complex is two sets of upper and lower.Conclusions1.In the goat model,the ultimate antedisplacemental distance of TCAF surgery was 8.0±0.2mm,which was well correlated with the average anteroposterior diameter of the antedisplacemental segment spinal canal and the average width of the vertebral bodies,and was linearly correlated with the average anteroposterior diameter of the antedisplacemental segment spinal canal.2.When the antedisplacemental segment consists of three vertebrae,the antedisplacemental complex after TCAF surgery can maintain a good stability,and the antedisplacemental complex with two sets of the fixation screws upper and lower can maintain a better and sufficient stability. |
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