Sagittal alignment changes of cervical spine in patients with cervical spondylotic myelopathy after cervical 3-7 single-door laminoplasty and its correlation with functional status of cervical spine

English Keywords:Cervical spondylotic myelopathy  Sagittal parameters of cervical spine  Laminoplasty  visual analog scale  modified Japanese Orthopaedic Association

English Abstract:

  【Abstract】 Objectives: To investigate the changes of sagittal alignment of the cervical spine after C3-7 single-door laminoplasty, and to explore its relationship with the functional status of cervical spine after laminoplasty. Methods: Retrospectively reviewed data of 164 patients between January 2015 and July 2018. There were 95 males and 69 females with an average age of 64.8±18.3(48-86) years. Follow up time: 22.7±11.3(9-46) months. Inclusion criteria: patients diagnosed of cervical spondylotic myelopathy. Exclusion criteria: previous history of spinal surgery, history of tumors, history of cervical trauma, sagittal spinal imbalance, scoliosis, spine infection. The C2-7 sagittal vertical axis(C2-7 SVA), cervical 1-2 Cobb angle, cervical 2-7 Cobb angle, cervical arc chord sistance(CACD), cervical tilting(CERT), cranial inclination(Cranial Tilting, CRAT), cervical global alignment(CGA), thoracic 1 slope(T1S) and cervical 7 slope(C7S) were measured and recorded using PACs 3.0 system. The neck pain visual analog scale(VAS) and modified Japanese Orthopaedic Association(mJOA) score before operation and at final follow-up were recorded. All data were analyzed by SPSS 24.0 software. Results: Compared with preoperative, T1S decreased by 1.25±3.34(21.38°±7.54° vs 20.13°±7.16°, P=0.004), C7S decreased by 0.44°±4.23°(28.05°±7.72° vs 27.61°±7.81°, P=0.012), C2-7 Cobb angle decreased by 5.51°±6.88°(15.92°±12.57° vs 10.40°±10.93°, P<0.001), CACD decreased by 1.50±3.92mm(6.94±5.69mm vs 5.44±5.52mm, P=0.003), CERT decreased by 2.23°±5.27°(13.45°±6.37° vs 11.22°±6.78°, P=0.001), C2-7 SVA increased by 3.35±9.90mm(18.20±9.05mm vs 21.55±10.65mm, P=0.009), C1-2 Cobb angle increased by 2.06°±5.09°(39.56°±0.46° vs 41.62°±0.70°, P=0.002), VAS (1.52±1.47) at final follow-up was significantly higher than that before operation(1.02±1.12)(P=0.007). Pearson correlation analysis showed that the changes of C2-7 SVA, CACD, CGA, C2-7 Cobb angle, C1-2 Cobb angle, CERT and CRAT were significantly correlated with each other(P<0.05). The difference of VAS before and after surgery were positively correlated with the difference of C2-7 SVA(r=0.462, P<0.001), C1-2 Cobb angle(r=0.362, P<0.01) and CRAT (r=0.323, P<0.01), and negatively correlated with the difference of CGA(r=-0.316, P<0.01) and CACD (r=-0.344, P<0.01). The changes of mJOA score before and after operation were positively correlated with the changes of C2-7 SVA(r=0.273, P<0.05) and C1-2 Cobb angle(r=0.298, P<0.05). Conclusions: The sagittal alignment of cervical spine in patients with cervical spondylotic myelopathy changed significantly after C3-7 single-door laminoplasty, including kyphotic changes of the lower cervical spine, forward tilting of gravity center of cervical spine, and overextension of the upper cervical spine and cervicothoracic spine. These changes were not only due to the influence of the cervical posterior structuraldamage, but also the compensatory mechanism. The deterioration of axial symptoms after cervical laminoplasty is related to the change of sagittal alignment of cervical spine.