| BACKGROUND:Anterior cervical decompression and fusion with internal fixation is considered as the gold standard of surgical treatment cervical spondylotic myelopathy. Anterior cervical plate fixation play an important role on restore the stability of cervical spine, reconstruction of cervical lordosis, maintain the normal disc height, prevent graft displacement and promote bone fusion, and achieve early mobilization of patients. Anterior midline screw fixation plate system has a good biomechanical properties, unique design, good biocompatibility and easy to operate. Anterior midline screw fixation plate system has been applied to a single-level or two adjacent anterior cervical discectomy and fusion (ACDF). The plate system has a unique midline single-screw fixation style, unlike other anterior plate with two screws in a vertebral body, the fixing screws on a plane. The biomechanics stability of its fixed, in particular, cervical lateral flexion and rotation state are concerns about by clinicians. Anterior cervical corpectomy and fusion with preserved posterior vertebral wall (PWCF) is an innovative optimization of anterior cervical corpectomy and fusion (ACF). PWCF can improve the surgical safety, increasing the fusion rate, maintain higher stability. PWCF has been widely used in clinical to treat cervical spondylotic myelopathy as its better biomechanics stability and safety. This study intends to use the unique anterior midline screw fixation plate system in anterior cervical corpectomy and fusion with preserved posterior vertebral wall (PWCF), expect good clinical results obtained. The scientific evidence need be provided for clinical application.Objective:1.To compare the biomechanical stability in a goat model of anterior cervical corpectomy and fusion with preserved posterior vertebral wall (PWCF), between one group plating with a midline screw fixation plate system and the other group plating with regular anterior cervical plate system, and to provide scientific evidence for clinical application.2. To study and evaluate the reliability and advantage of a midline screw fixation plate system and internal fixation on anterior cervical corpectomy and fusion with preserved posterior vertebral wall (PWCF).Methods:1. To test the biomechanical stability,8 cervical spine specimens-of goat were used. Biomechanics of fresh cervical specimens was compared to measure three-dimensional range of motion (ROM) between three group:intact specimens, PWCF plating with the midline screw fixation plate system, and PWCF plating with conventional anterior cervical plate system. The ROM of each C2-4 level were tested in flexion, extension, lateral bending and axial torsion condition sequentially. All date were analyzed statistically with SPSS 13.0 software.2. To study the clinical reliability and advantage, 41 cases of two-level CSM patients who underwent PWCF and the midline screw fixation plate system internal fixation were involved in study group and all cases were followed up for 6 months. Another previous 39 cases of two-level CSM patients who underwent PWCF and conventional anterior cervical plate internal fixation, followed up for above 6 months, were involved in control group. The operation duration, quantity of blood loss associated with the operation, post-operative complications rate, primary fusion rate and intervertebral height changing rate between two groups were contrasted. Pre-and post-operative neurological function was evaluated according to JOA score standard, and thus clinical efficacies between two groups were contrasted. All date were analyzed statistically with SPSS 13.0 software.Results:1.The ROM of study group plating with the midline screw fixation plate system, in flexion:4.63±0.57, in extension:8.34±0.45, in lateral bending:15.35±0.09, and in axial torsion condition:4.21±0.53. Compared with intact specimens, in flexion, the ROM decreased 71%, the difference was significant(P<0.05); in extension, the ROM decreased 62%, the difference was significant(P<0.05); in lateral bending, the ROM decreased 52%, the difference was significant(P<0.05); and in axial torsion condition, the ROM decreased 25%, the difference was significant(P<0.05)。Compared with control group plating with conventional anterior cervical plate system, in flexion, the difference was no significant(P>0.05); in extension, the difference was no significant(P>0.05); in lateral bending, the difference was no significant(P>0.05); and in axial torsion condition, the difference was no significant(P>0.05)。2. The operation duration and the quantity of blood loss associated with the operation in the midline screw fixation plate system group were lower than that in conventional anterior cervical plate system fixation group and the differences between two groups had obvious statistical significance (P<0.05). There was no statistically significant difference on the post-operative complications rate between two groups (P>0.05). The post-operative JOA scores in both groups showed significant improvement as compared with the pre-operative status. Nevertheless there was no statistically obviously significant difference on the total excellent and good rate between two groups (P>0.05). There were also no statistically significant difference on the primary fusion rate and intervertebral height changing rate between two groups (P>0.05). Conclusion:1.The biomechanics stability of fresh goat cervical specimens after PWCF plating with the midline screw fixation plate system is satisfactory, there were no statistically significant difference with control group.2. Anterior midline screw fixation plate system had obvious advantages over conventional anterior cervical plate on application to PWCF and internal fixation for treating two-level cervical spondylotic myelopathy. Under the promise of clinical efficacy, primary fusion rate and intervertebral height changing rate, Anterior midline screw fixation plate system could simplify surgical procedure, save operation time and minimize the quantity of blood loss associated with the operation. |
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