[Analysis of correlative factors of spinal cord posterior displacement after single door laminoplasty].

Objective: To observe the open angle (OA), cervical curvature angle (CA), preoperative spinal cord compression rate(PSCR), postoperative spinal cord shift (PSCS) in patients with chronic compressive cervical myelopathy undergoing C3-7 single open laminoplasty, and to explore the possible mechanism and influencing factors of postoperative average spinal cord drift, so as to provide objective basis for predicting PSCS.

Methods: From May 2012 to July 2016, 32 patients with multi-segmental chronic compressive cervical myelopathy who underwent single-door laminoplasty in our department were analyzed retrospectively, including 14 cases of cervical spondylotic myelopathy, 8 cases of developmental cervical spinal stenosis with cervical myelopathy, and 10 cases of ossification of posterior longitudinal ligament. The OA of cervical spine was measured on CT, the CA was measured on X-ray, the PSCR and PSCS were measured on MRI. The patients were divided into two groups according to PSCS(group A>=2.5 mm, group B<2.5 mm). In the group A, there were 11 males and 6 females, with an average age of (56.58±9.80) years old, a mean course of the disease of (23.52±7.86) months; while in group B, there were 6 males and 9 females, with an average age of (58.46±12.53) years old, a mean course of disease of (21.13±7.75) months. The correlation analysis between PSCS and OA, CA and PSCR was performed, and multiple linear analysis of correlated parameters was carried out.

Results: The OA in group A was (40.47±9.45) °, in group B was (27.84±5.67) °. The OA in group A was higher than that in group B (<0.01), and OA was moderately correlated with PSCS (=0.794, =0.000). The CA was(11.56± 4.99) ° in group A and(6.64±3.28) ° in group B . The CA in group A was higher than that in group B (<0.01), and CA was moderately correlated with PSCS (=0.632, =0.000). The PSCR was (27.70±2.92) % in group A , was (24.59±2.80) % in group B . The PSCR in group A was higher than that in group B(<0.01), PSCR was moderately correlated with PSCS(=0.667, =0.000). The CA dependent variable was kicked out(>0.1), and the partial regression coefficients of OA and PSCR were 0.113 and 0.059 respectively.

Conclusions: PSCS is the result of OA, CA and PSCR, among which PSCR has the most important influence, OA is the second, CA is the least. PSCS can be predicted by 0.059×OA+0.113×PSCR-2.266 equation, which provides a theoretical basis for preoperative evaluation of spinal cord decompression after surgery.