Analysis of related factors of posterior shifting of the spinal cord after cervical laminoplasty / 中华骨科杂志

ABSTRACT

Objectives To investigate influencing factors and pattern of posterior shifting of the spinal cord after cervical laminoplasty.Methods Forty three patients with compressive cervical myelopathy,including 32 males and 11 females,aged from 33 to 78 years (average,57.9 years),treated with open-door laminoplasty from C3 to C7 between February 2008 and October 2010,were enrolled in this study.There were 30 cases of cervical spondylotic myelopathy with developmental cervical stenosis and 13 cases of ossification of the posterior longitudinal ligament.Twenty one cases underwent modified open-door laminoplasty using anchor method,and the other 22 cases underwent laminoplasty with preservation of the unilateral muscular ligament complex.According to midsagittal T2-weighted MRI in the neutral position,several parameters indicating shift distance of the spinal cord and dural sac were measured at each level before operation and at 3 months after operationshift of anterior margin of the spinal cord (SAMSC),shift of posterior margin of the spinal cord (SPMSC),shift of anterior margin of the dural sac (SAMDS) and shift of posterior margin of the dural sac (SPMDS).The line connecting the top of dens and posterior inferior angle of T1 was defined as E line and the length was E.The length of perpendicular line from each base point to E line was Px (x =1-6).The parameter (100×Px/E) was used to represent local curvature at each level,and the curvature index (CI)was used to represent the global curvature of the cervical spine.Then correlation analyses of the parameters above were performed.Results There was no significant change in SAMDS at different level after surgery,however SAMSC,SPMSC and SPMDS changed significantly and synchronously.At the level of C5 and C6,SPMSC was maximum,but not correlated to CI.Actually,SPMSC was correlated to the local curvature and highly correlated to SPMDS at the same level.Conclusion After cervical laminoplasty,posterior shifting of the spinal cord was highly correlated to posterior shifting of the dural sac at the same level,weakly correlated to local curvature and not correlated to the global curvature of the cervical spine.