Factors that regulate spinal cord position after expansive open-door laminoplasty

Although appropriate dorsal migration of the spinal cord is a desired end point of cervical laminoplasty, it is difficult to predict in advance the spinal cord position after surgery and to control it during surgery. The aim of the present study was to investigate the factors that affect postoperative spinal cord position after cervical laminoplasty using multivariable analysis.

We retrospectively assessed 56 consecutive patients with cervical spondylotic myelopathy treated by open-door laminoplasty. The postoperative anterior space of the spinal cord was measured at 204 levels, and its maximum value was measured at 56 levels within the decompressed area. To identify the factors that regulate the postoperative spinal cord position, we evaluated seven radiological parameters, including the C3-C7 lordosis angle (LA), LA of the decompressed area, C3-C7 spinal cord lordosis angle (SCLA), SCLA of the decompressed area, spinal canal sagittal diameter at C5, number of expanded lamina, and postoperative dural sac diameter.

The postoperative anterior space of the spinal cord was 5.5 ± 1.4 mm, and its maximum value was 6.4 ± 1.3 mm. A multiple linear regression analysis revealed that the number of expanded laminae (standardized partial regression coefficient: β = 0.17, p = 0.009) and dural sac diameter (β = 0.43, p < 0.001) was significantly associated with anterior space of the spinal cord. Although these parameters were also significantly associated with the maximum value, their relative contributions were reversed; β = 0.49 (p < 0.001) for the number of expanded laminae and 0.25 (p = 0.029) for the dural sac diameter.

The number of expanded laminae and dural sac diameter was significantly associated with the spinal cord position after laminoplasty. These factors could help to predict spinal cord position following laminoplasty and achieve adequate indirect decompression of the spinal cord.