Abstract：Objective To investigate the clinical features, pathological mechanism and predisposing factors of postoperative axial pain (PAP) after unilateral expansive laminoplasty for treating cervical stenotic myelopathy (CSM). Methods The clinical data on 79 CSM patients with no less than four segments who underwent unilateral expansive laminoplasty secured with consecutive mini-plates on the open side was retrospectively analyzed. These patients were followed up for a minimum of 24 months. The constituent ratios of preoperative cervical instability, postoperative corrected amplitudes of Cobb angle of cervical curvature, the lordosis index, range of motion between flexion and extension, mid-sagittal canal diameter, Pavlov ratio, open-laminar angle, cross-sectional area of the dural sac within different realms were compared between PAP and non-PAP groups. Univariate logistic regression analysis was used to confirm the influence of these parameters on the occurrence of PAP. Multivariate logistic non-linear regression analysis was conducted to further verify the correlation between the onset of PAP and parameters of P<0.10 filtered by preliminary confirmation based on univariate logistic regression analysis. The proportion of patients with different alteration degrees of intervertebral motion of cervical segments between preoperative unsteadiness and steadiness groups was calculated. Results Twelve patients with PAP received conservative treatment and achieved rehabilitation during the final follow-up. The results of univariate logistic regression analysis suggested preoperative cervical instability, the open-laminar angle, correction of the postoperative range of motion and lordosis index were related to the incidence of PAP (P<0.10). Obvious decrease of postoperative motion and preoperative instability were independent risk factors for predicting the occurrence of PAP via multivariate logistic regression analysis (P<0.05). The proportion of preoperative cervical instability in the PAP group was higher than in the non-PAP group, with statistically significant difference (P<0.05). The incidence of pronounced decrease of the range of motion in the PAP group was higher than in the non-PAP group, and the difference was of statistical significance (P<0.05). The rate of notable decrease of the range of motion in the preoperative unsteadiness group was significantly higher than in the steadiness group. Conclusions PAP is more likely to reoccur regularly accompanied by excessive loss of the range of motion after surgery if preoperative unsteadiness is due to the treatment of CSM. It is proposed that mini-plates should be used to fix steadiness segments, however, the hybrid system of lateral mass or pedicle screws and rods can be applied in preoperative unsteady segments to reduce the incidence of postoperative cervical instability and PAP.
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2020, Vol. 31 
