# Biomechanical Analysis of Posterior Ligaments of Cervical Spine and Laminoplasty
## 4 Discussion  
This study aimed to investigate the laminoplasty with/without LF of posterior ligaments on the cervical spine biomechanics using a validated model of C2-C7 spine. There are two types of spinal cord injuries for CSM, CDH, and C-OPLL: Static and dynamic compression. The causes for static damage include congenital spinal stenosis, cervical disc herniation, osteeophytosis, and ligamentous hypertrophy [29; 30]. The causes for dynamic compression injury include translation and angulation of the spinal column or overlapping of the lamina (pincor mechanism) and buckling of the ligamentum flavour (LF) [31; 32; 33]. Laminoplasty as extensive posterior decompression is suitable for cervical spinal cord myelopathy resulting from static and dynamic compression. Modifications in the current procedures are being suggested by clinicians to address the current surgical complications for the increased kyphosis and axial pain. In recent years, minimally invasive methods for laminoplasty, such as selective laminoplasty, skip laminectomy, and endoscopic laminectomy, have been reported and have shown promising clinical outcomes [17; 18; 19; 34; 35; 36]. [PERSON] reported on the development of double-door  
Figure 8: Facet contact forces. (**a**) Extension, (**b**) lateral bending, (**c**) axial rotation. Vertical axis is force (N), horizontal axis is each intervertebral level. laminoplasty. At first, a pyramidal-shaped osteotomy is made at the cranial base of the spinous process to obtain a good visual field. Next, the remaining part of the spinous process is split centrally from its surface, and the split portion is connected to the pyramidal-shaped dome [16]. [PERSON] conducted articular segmental decompression surgery using endoscopy (cervical microendoscopic laminotomy) for cervical spondylic myelopathy and reported patients to have similar neurological outcomes to conventional laminoplasty, with significantly less postoperative axial pain and improved subaxial cervical lordosis [17]. [PERSON] proposed a skip laminectomy method that preserved the attachments of the semispinals cervicis and multifidus muscles on the cervical spinous processes and limited the damage to the attachments of the interspinous and rotator muscles [18]. [PERSON] proposed performing selective laminoplasty on subjects diagnosed with CSM at a single intervertebral level or two consecutive intervertebral levels based on preoperative neurological symptoms and imaging findings. They concluded that the clinical outcomes of selective laminoplasty were similar to the C3-C7 laminoplasty with significantly less operation time and blood loss, compared with conventional C3-C7 laminoplasty [19]. The fundamental purpose of these techniques is to figure out ways on how to avoid damaging the posterior soft tissues, including ligaments. The studies of injuring the posterior ligamentous structures of the cervical spine indicated that each structure contributes to cervical stability [14,37]. The SS, IS, and LF were reported to restrain flexion equally in a porcine model [15]. However, there has been no FE model analysis of the effect of damaging the posterior ligaments on the cervical spine in laminoplasty. Studying the biomechanics of laminoplasty of the cervical spine can be divided into the FE model and cadaver analysis. However, there are few analyses of laminoplasty models in the literature. [PERSON] compared intact, laminectomy, and double-door laminoplasty models for spinal cord [38]. [PERSON] reported that the stabilities of the hinge sides of plate-augmented open-door laminoplastics based on cutting in a curved or straight line were compared using a FE model and the potential of the proposed technique to reduce the risk of hinge fracture and displacement [39]. [PERSON] analyzed biomechanical changes in the spinal cord and nerve roots following the open-door and double-door laminoplasty for OPLL [40]. However, none of the studies have reported on the effect of preserving/resecting the LF ligament.