A Biomechanical Comparison Of Goat After Cervical Single And Double-door Laminoplasty With Reconstruction Of The Posterior Ligamentous Complex

Objective: Posterior decompression procedures, such as the laminectomy and laminoplasty procedures are generally considered the procedures of first choice for treatment of multilevel cervical spondylosis. The conventional cervical laminectomy and the cervical laminoplasty must remove the total or partial cervical spinous process including the supraspinous and interspinous ligaments what attached to the spinous process. These procedures destroied the integrity of the posterior cervical ligamentous complex, and led to some complications, such as the disappearance of the lordotic alignment, the unsteadiness of the cervical spine, door re-closure and the axial symptoms, and so on. The use of the laminoplasty with reconstraction of the posterior cervical ligamentous complex could reduce those complications. There have been numerous considerable studies showed that the method has obvious superiority to maintain the stability of cervical spine, but no experimental study report the biomechanical difference between cervical single and double-door daminoplasty with reconstruction of the posterior ligamentous complex. To compare the biomechanical effects of the two procedures, we carried out biomechanical experiments on the fresh cervical spine specimens of goat, and measured the biomechanical character of the intact specimens, the specimens of single and double-door laminoplasty with reconstruction of the posterior cervical ligamentous complex, respectively.Methods: We studied 24 fresh cervical spine specimens (C2~T2) of goat what were randomly separated into three groups. There are 8 specimens in each group. Group A (intact specimens group): removed all anterior muscles of the cervical spine, reserved the integrity of posterior muscles, the ligaments and the membrana capsularis of the facet joint; Group B (single-door laminoplasty with reconstruction of posterior cervical ligamentous complex): on the base of group A, we performed single-door laminoplasty with reconstruction of posterior cervical ligamentous complex; Group C(double-door laminoplasty with reconstruction of posterior cervical ligamentous complex), based on the group A, double-door laminoplasty with reconstruction of posterior cervical ligamentous complex was performed. We poured the dental base acrylic resin powder plate what were paralleled to each other on the two ends of the specimens, ensuring the two ends of the specimens in the centre of the plates. Kept the two plate paralleled to each other and in a straight line. Labeled the centre of the plates (i.e. the vertebra median in the sagittal plane of the C2 and T1) and the vertebral sagittal centre in the lateral plane. We used biomechanical testing machine to test the specimens. We performed flexion experiment, axial extension experiment (including: axial compression experiment, anterior loading experiment and posterior loading experiment) respectively in each group.The specimens became straight from lordotic alignment in the flexion experiment and extension experiment. The deformation of the specimen when it was straight in the flexion experiment represents the vertical dimension from the apogee of the anterior arch to the corresponding string (the height of the anterior arch). The loading power what made the specimens became straight represents the resistance of the posterior cervical ligamentous complex in the flexion experiment and the extension experiment. The posterior cervical ligamentous complex in the anterior loading experiment offered the initial resistance, so we concentrated to measure and analysis the data which reflected the functions of the posterior cervical ligamentous complex. We recorded the deformation of the specimen when the loading value was 10N in the flexion and extension experiment, the loading value and the deformation of the specimen when the three points (the vertebra sagittal median of C2, C5, T1) were in a straight line, the deformation of the specimen when the loading value was 100N; measured the deformation of the specimen when the loading value was 10N, 50N, 100N in the anterior loading experiment; recorded the deformation of the specimen when the loading value was 100 N in the axial loading experiment; and the deformation of the specimen when the loading value was 50N in posterior loading experiment .Results: 1. The deformation of the specimen when it was straight represents the height of the anterior arch. There was no significant different between group A and group B and group C(p>0.05).2. The loading power made the specimens became straight represents the resistance of the posterior cervical ligamentous complex in the flexion experiment. There was no significant different between group A and group B and group C(p>0.05).3. The loading power what made the specimens became straight also represents the resistance of the posterior cervical ligamentous complex in the extend experiment. There was no significant different between group A and group B and group C(p>0.05).4. The posterior cervical ligamentous complex in the anterior loading experiment offered the initial resistance and there was no significant different between group A and group B and group C(p>0.05).Conclusion: On the function of tensile stress, there was no significant different between single and double-door laminoplasty with reconstruction of the posterior cervical ligamentous complex and intact spine. Both single and double-door laminoplasty with reconstruction of the posterior cervical ligamentous complex utmostly reserved the function of the posterior cervical ligamentous complex. There was important clinical significance of reconstructing the integrity of the posterior cervical ligamentous complex during the operation: it could maintain the lordotic alignment of cervical spine, antagonize the tensile stress produced by anterior flexion of cervical spine, maintain the stability of cervical spine and prevent postoperative complications.