Relationship between clinical outcomes and changes of cervical sagittal alignment after cervical expansive door-open laminoplasty in ossification of posterior longitudinal ligament

English Keywords:Ossification of posterior longitudinal ligament  One-door-open laminoplasty  Sagittal alignment  Clinical outcome

English Abstract:

  【Abstract】 Objectives: To analyze the relationship between the changes of cervical spine sagittal alignment and clinical outcomes after cervical expansive door-open laminoplasty in patients with ossification of posterior longitudinal ligament(OPLL). Methods: 68 patients with OPLL who underwent cervical expansive door-open laminoplasty between January 2009 and January 2013 were analyzed in this study. All the patients were followed up from 12 to 30 months. Outcome assessment JOA scores, VAS scores were obtained in all patients preoperatively, postoperatively and at last follow-up, the JOA improvement rate(IR) was also calculated. Standing radiographs of cervical spine, CT(3D) and MRI were obtained preoperatively, postoperatively and at last follow-up. Cervical spine alignment was assessed with the following 3 parameters: C2-C7 Cobb angle, C2-C7 sagittal vertical axis(SVA) and T1 slope. Results: At last follow-up, VAS and JOA scores improved significantly(P<0.001) when compared with the preoperative scores, the JOA improvement rate was excellent in 21 cases, good in 30 cases, middle in 14 cases and poor in 3 cases, the excellent rate was 75%. C2-C7 Cobb angle increased from 15.4°±9.5° preoperatively to 17.4°±10.2° at last follow-up, but there was no significant difference(P=0.166); C2-C7 SVA increased from 21.0±15.3mm to 27.0±15.7mm, the difference was significant(P=0.009); T1 slope angle increased from 30.2°±10.1° to 33.7°±8.0°, the difference was significant(P=0.044). There was a linear correlation and positive correlation between T1 slope angle and C2-C7 Cobb angle(r=0.569, P<0.01), T1 slope angle and C2-C7 SVA(r=0.544, P<0.01) preoperatively. At last follow-up, C2-C7 Cobb angle increased in 44 patients and decreased in 24 patients, C2-C7 SVA angle increased in 46 patients and decreased in 22 patients. However, the improvements of JOA and VAS scores were not significant different between the patients who had increased C2-C7 Cobb angle and patients who had decreased C2-C7 Cobb angle, the patients who had increased C2-C7 SVA angle and patients who had decreased C2-C7 SVA(P>0.05). Conclusions: Neurological function improves after expansive door-open laminoplasty in patients with OPLL, but the cervical alignment changes after surgery are not significantly correlated with the clinical outcomes.