Background: Posterior translation of the spinal cord occurs passively following laminoplasty with the presence lordotic spine and availability of a space for the spinal cord to shift. This study is to predict the distance of posterior spinal cord migration after expansive laminoplasty at different cervical levels based on measurement of posterior translation of the spinal cord in normal cervical morphometry.
Methods: Measurements were performed from C34, C45, C56 and C67 disc using magnetic resonance imaging (MRI) images. Apical level of the cervical curve, lordotic angle, spinal cord diameter, spinal canal diameter, space anterior to the cord and spinal canal/cord ratio were determined before and after postulated laminoplasty. Statistical analysis was performed to assess the significance of the canal enlargement and effective spinal cord decompression at each level.
Results: The predicted spinal canal decompression achieved at C34, C4C5, C56 and C67 levels were 48.8, 71.9, 84 and 86.5%, respectively. The mean measurement of spinal canal after laminoplasty was 16.7 mm with spinal canal diameter increased between 3.5 and 5.6 mm. Space anterior to the cord after laminoplasty increased to between 8.6 and 10.9 mm. There was significant correlation between Cobb's angle and spinal canal diameter post laminoplasty at C45, C56 and C67 but no significant correlation between Cobb's angle and space anterior to the cord post laminoplasty was found.
Conclusions: Laminoplasty may produce larger canal expansion at the lower cervical spine compared to the upper cervical area; therefore, the outcomes of those who have predominantly higher cervical myelopathy were inferior to those who have lower cervical myelopathy.