Cervical spondylosis is a degenerative disease. The main causes include chronic fatigue, cervical disc herniation, osteogenesis, arthritis, ligament thickening and ossification, and trauma. These disorders cause severe clinical symptoms due to compression to the spinal cord, nerve roots, vertebral arteries, and sympathetic nerves . Cervical spondylosis is divided into four types: cervical spondylotic myelopathy, cervical spondylotic radiculopathy, arteria vertebralis, and sympathetic cervical spondylosis . For most patients, conservative symptomatic treatment with medications, acupunctures, tractions, and massages could relieve symptoms. However, for a few patients, conservative treatment may not be effective, and the symptoms may be aggravated over time, causing continuous pain. Posterior cervical surgery has been used as an alternative method since 1950 to treat cervical spondylosis. The advantage of posterior cervical spine surgery is that it avoids damage to the trachea, esophagus, important blood vessels, and nerves in front of the cervical spine, thus reducing the risk of surgery . However, the posterior cervical spine also has its own defects, which can break down in the rear of the cervical muscle ligament complex, result in the destruction of the cervical vertebra rear anatomical structure and loss of stability [28, 29], and cause post-operative stiffness, acid bilges, and pain in the neck, shoulder, and back, called axial symptoms (AS) . After decades of development, single open-door laminoplasty has become a major surgical method for the treatment of multilevel cervical spondylotic myelopathy . To alleviate axial symptoms after surgery, this surgical method has been continuously improved in clinical work, including posterior reconstruction, minor invasive surgery, and internal fixation [30–32]. In reconstructive surgery, expanded laminoplasty with preserved posterior spinous ligament complex proposed by Kawaguchi et al. could significantly alleviate axial symptoms in patients after surgery . This modified surgical method restores the anatomical structure of the back of the cervical vertebra to the full extent, increasing the stability of the cervical vertebra after surgery, guaranteeing the physiological curvature and post-operative mobility of the cervical vertebra.
We conducted this retrospective study to further explore whether modified single open-door laminoplasty with reconstruction of the posterior spinous ligament complex (MLRP) has a significant effect on relieving axial symptoms after surgery and explore the possible factors leading to this result. Through analysis of the collected data, we found that the occurrence and severity of post-operative axial pain were not correlated with age, gender, operation time, intraoperative blood loss, and post-operative drainage volume of patients. In terms of the post-operative VAS scores, there was no statistical difference in the incidence of axial pain 1 month after surgery between groups A and B; However, the difference was significant 3 months, 6 months, and 1 year after surgery. The procedure did not reduce the incidence of post-operative axial pain in the first month post-surgery, but during the next follow-up from 3 months to 1 year, the incidence of AS in group A was significantly lower than in group B. No patients in group A no longer suffered from severe axial pain 1 month after surgery, while the patients in group B still suffered from severe axial pain until 1 year after surgery. Generally speaking, compared with traditional single open-door laminoplasty, the modified surgical method with reconstruction of the posterior spinous ligament complex has obvious advantages in relieving patients' post-operative axial pain. The occurrence of post-operative axial pain in group A was significantly lower than in group B.
To study the reasons leading to this advantage, we measured the preoperative and post-operative X-rays of the patients in groups A and B, calculated the cervical curvature index (CCI) value of the patients, and conducted a statistical comparison. In group A, the comparison of the CCI values before and after surgery was not statistically changed, while in group B, the CCI values before and after surgery was statistically decreased. In addition, the changes between postoperative CCI and preoperative CCI in the two groups was also statistically significant. This proves that traditional single open-door laminoplasty significantly changes the curvature of patients' cervical vertebra because of instability and destroys the posterior cervical muscle-ligament complex and spinous processes. The instability of the cervical spine after single open-door laminoplasty was regarded as the main reason for the reduction in post-operative axial pain, leading to post-operative rehabilitation.
However, MLRP may protect the muscles and ligaments that maintain the stability of the cervical spine. We analyzed the pre- and postoperative CT slices on the cervical back muscle cross-sectional areas. The results showed that the change in the value of the posterior cervical muscle cross-sectional area in group A was significantly lower than in group B, which may be because simple single open-door laminoplasty destroys the adhesion point of the muscle behind the spinous process, leading to significant post-operative muscle atrophy. This may be another important factor in the relief of post-operative axial pain in patients who undergo MLRP.
This retrospective study confirmed that MLRP could be of considerable significance in relieving patients' AS after surgery. Two relative factors are post-operative changes in the cervical curvature index and the cross-sectional area of the posterior cervical muscles. MLRP protects the posterior cervical muscles and prevents instability of the cervical spine via the reconstruction of the posterior cervical muscle-ligament complex and spinous processes. This study provides a novel alternative surgery to decrease axial pain in patients with cervical spondylotic myelopathy.