[Correlation analysis of preoperative T 1 slope in MRI and physiological curvature loss after expansive open-door laminoplasty].

Objective:To investigate whether preoperative T 1 slope (T 1S) in MRI can predict the changes of cervical curvature after expansive open-door laminoplasty (EOLP) in patients with cervical spondylotic myelopathy, so as to make up for the shortcomings of difficult measurement in X-ray film. Methods:The clinical data of 36 patients with cervical spondylotic myelopathy who underwent EOLP were retrospectively analysed. There were 21 males and 15 females with an average age of 55.8 years (range, 37-73 years) and an average follow-up time of 14.3 months (range, 12-24 months). The preoperative X-ray films at dynamic position, CT, and MRI of cervical spine before operation, and the anteroposterior and lateral X-ray films at last follow-up were taken out to measure the following sagittal parameters. The parameters included C 2-C 7 Cobb angle and C 2-C 7 sagittal vertical axis (C 2-C 7 SVA) in all patients before operation and at last follow-up; preoperative T 1S were measured in MRI, and the patients were divided into larger T 1S group (T 1S>19°, group A) and small T 1S group (T 1S≤19°, group B) according to the median of T 1S, and the preoperative T 1S, C 2-C 7 Cobb angle, C 2-C 7 SVA, and the C 2-C 7 Cobb angle and C 2-C 7 SVA at last follow-up, difference in axial distance (the difference of C 2-C 7 SVA before and after operation), postoperative curvature loss (the difference of C 2-C 7 Cobb angle before and after operation), the number of patients whose curvature loss was more than 5° after operation, and the number of patients whose kyphosis changed (C 2-C 7 Cobb angle was less than 0° after operation). Results:The C 2-C 7 Cobb angle at last follow-up was significantly decreased when compared with preoperative value ( t=8.000, P=0.000), but there was no significant difference in C 2-C 7 SVA between pre- and post-operation ( t=-1.842, P=0.074). The preoperative T 1S was (19.69±3.39)°; there were 17 cases in group A and 19 cases in group B with no significant difference in gender and age between 2 groups ( P>0.05). The preoperative C 2-C 7 Cobb angle in group B was significantly lower than that in group A ( t=-2.150, P=0.039), while there was no significant difference in preoperative C 2-C 7 SVA between 2 groups ( t=0.206, P=0.838). At last follow-up, except for the curvature loss after operation in group B was significantly lower than that in group A ( t=-2.723, P=0.010), there was no significant difference in the other indicators between 2 groups ( P>0.05). Conclusion:Preoperative larger T 1S (T 1S>19°) in MRI had a larger preoperative lordosis angle, but more postoperative physiological curvature was lost; preoperative T 1S in MRI can not predict postoperative curvature loss, but preoperative larger T 1S may be more prone to kyphosis.