Multilevel CDM, which is characterized by multisegmental spinal cord compression, is a common spinal disorder all over the world. Cervical kyphosis associated with multilevel CDM is the result of progressive subluxation of the apophyseal joints because of degenerative changes in the facet joints and discs . Laminoplasty has been proved to be an effective and safe treatment for multisegmental lesions to widen the spinal canal without removing the dorsal elements of the cervical spine. In the past decades, lateral mass screws fixation has become optimal preferred option for stabilizing the cervical spine and correcting kyphotic deformity when multilevel decompression is required . During the follow-up period, we also observed that some patients suffered the so-called axial symptoms including nuchal pain, neck stiffness and shoulder pain, which affect their quality of postoperative life seriously. The optimal surgical procedure for multilevel CDM accompanying kyphosis remains controversial due to the above shortcomings.
At the postoperative follow-up, correction of cervical kyphosis in Group LCS was better than that in Group LP; the difference was statistically significant between the groups. Based on the biomechanical study , the physiologic lordosis of the cervical spine plays an important role in maintaining normal neurological function. This emphasizes the importance of early recognition of complications caused by cervical curvature changes. There is controversy on the issue: Is the correction of cervical curvature related to neurological recovery rate and axial symptoms?
In the present study, better neurological improvement was both obtained in laminoplasty and laminectomy with fixation; there was no significant difference between groups LP and LCS. Our results in short-term follow-up did not demonstrated that correction of cervical kyphosis was correlated with neurological improvement. Zhang et al  suggested that loss of cervical lordosis after laminoplasty contributed to kyphotic alignment change, which prevented indirect decompression via posterior cervical spinal cord shift and led to postoperative residual anterior compression of cervical spinal cord; thus, progressive kyphosis results in late neurological deterioration in long-term follow-up of laminoplasty. Based on previous results  for an average 9.17 years’ follow-up of 98 patients undergoing posterior operations, we revealed that loss of CI was positively correlated with poor neurological recovery, especially in the patients with laminectomy alone, and presumed that segmental and kyphotic instability could be the main cause of poor neurological recovery in the long-term follow-up. Conversely, in the current study, we insisted that adequate decompression of the spinal cord in the operation may be a pivotal factor in early postoperative neurological recovery, which was not yet clearly associated with correction of cervical kyphosis. This result was in agreement with recent reports [18–20], indicating that there were no correlations between cervical sagittal alignment parameters and postoperative outcomes for the patients with maintained cervical lordosis who underwent posterior decompression and fusion at 1-year follow-up.
At the postoperative follow-up, 32.11% (35/109) of the entire group experienced axial symptoms, an incidence consistent with previous studies. The incidence of axial symptoms was 45.28% (24/53) for group LP and 19.64% (11/56) for group LCS, respectively; the difference was statistically significant. The incidence of axial symptoms after open-door laminoplasty can be as high as 5–86% , but the exact etiological mechanism remains uncertain. Wang et al  believed that the destruction of cervical structures and detachment of posterior muscles, which increased cervical flexion mechanical stress, may play a pivotal role in the pathogenesis of AS. The spinous process, which was reconstructed firmly in the midline with titanium plates and enhanced it using nonabsorbable sutures with a high fusion rate and good stability, was beneficial for early postoperative exercises and improving cervical-spine activity; thereby, this may improve postoperative AS and decrease the loss of cervical range of motion . Application of rigid internal fixation can reduce the incidence of advanced AS because it can enhance the stability of cervical vertebrae and reduce irritation in nearby soft tissues . In present study, cervical kyphosis was corrected and reconstructed in Group LCS, whose incidence of axial symptoms was significantly lower than that in Group LP. The present study showed that axial symptom severity was negatively correlated with cervical kyphotic correction, which also meant that neck pain would be improved significantly if the cervical kyphosis was corrected effectively.
However, some patients at the postoperative follow-up did not complain of neck pain (group LP 29/53; group LCS 45/56). Although the patients of two groups complained more or less of neck pain after surgery in short time, neck pain was gradually improved with the correction of cervical lordosis and strengthening of cervical stability. Chen et al  insisted that LP with preservation of unilateral posterior muscle-ligament complex (PMLC) (including paravertebral muscles, as well as the nuchal ligament and attachment sites between extension muscles and spinous process) had the advantage of less soft-tissue detachment and provided greater stability, as well as better muscular alignment and reduced postoperative AS. There were ample studies [26, 27] demonstrating that reducing the invasion of the cervical extensor, retaining muscles attached to the spinous process significantly lowered the incidence of AS and decreased the loss of sagittal cervical lordosis after surgery. Moreover, early postoperative extensor muscle rehabilitation protocols all likely play a role in prevention or limitation of neck pain following laminoplasty . Axial symptoms might also be caused by other problems, such as destruction of facet joints, intraoperative nerve root damage and hinge side nonunion. In short, axial symptoms were the results of a complication induced by multifactor and multimechanism after posterior cervical surgery, and the explicit pathogenesis remains to be further investigated.
Therefore, we thought that successful treatment of multilevel CDM with kyphosis required not only adequate decompression of the spinal cord, but also correction of cervical kyphosis as much as possible to avoid the surgery-related complications caused by sagittal malalignment or instability. There are several limitations need to be considered in our study. Over the last decade, many modified anterior or posterior surgical approaches for the treatment of multilevel CDM with kyphosis, including multilevel anterior cervical discectomy with fusion , modified unilateral open-door laminoplasty with PMLC preservation , laminoplasty with titanium miniplates fixation [30, 31] and combined anterior- posterior fusion, had been developed and obtained favorable outcomes, and additionally reduced the incidence of the long-term surgery-related complications. This study still needs other parameters to comprehensively evaluate the results, including T1 slope, C2-7 ROM, C2-7 sagittal vertical axis (C2-7 SVA) and cephalad vertebral level undergoing laminoplasty (CVLL). Subsequently, there is still a need for prospective, large-scale, multi-center clinical trials to further confirm our results.