Influences On Cervical Sagittal Parameters After Expansive Open-door Laminoplasty Extended To C1 And C2

Objective:To explore the effect of expansive open-door laminoplasty(EODL)extended to C1 and C2 on cervical sagittal parameters.Methods:A retrospective analysis included 25 patients with ossification in the posterior longitudinal ligament(OPLL)of upper cervical spine who underwent posterior EODL from February 2013 to December 2015.Among 25 patients,six underwent EODL extended to C1 and C2,and the other 19 received C2-7 EODL.Furthermore,the changes of C0-2 Cobb angle,C1-2 Cobb angle,C2-7 Cobb angle,C2-7 SVA and T1-Slope in lateral X-ray of cervical spine were measured before and after operation,and during the last follow-up,respectively.Results:In patients who underwent C1 and C2 EODL,C0-2 Cobb angle increased from(19.0±6.2)° preoperatively to(21.8±5.1)° at the last follow-up;however,no significant differences were observed between the two groups(P=0.083).Besides,there was no significant difference in C1-2 Cobb angle between pre-operative and final follow-up [(21.0±5.9)° vs.(24.8±4.5)°].Furthermore,significant statistical differences were found in C2-7 Cobb angle [(20.6±6.2)° vs.(13.8±6.9)°;P=0.001],C2-7 SVA [(18.8±4.9)mm vs.(28.6±8.4)mm;P<0.001],and T1-Slope [(20.3±7.5)° vs.(27.1±5.5)°;P<0.001] preoperatively when compared to those at the last follow-up.In addition,C2-7 SVA revealed no significant correlation with C0-2 Cobb angle(Pearson=0.189,P=0.365),while it was significantly correlated with T1-Slope(Pearson=0.717,P<0.001).Conclusion:Compared to traditional C3-7 EODL,expansive open-door laminoplasty extended to C1 and C2 was superior in achieving good clinical effect and avoiding stability destruction of the upper cervical spine based on the extended scope of surgery.However,certain disadvantages were also identified,such as loss of cervical spine,increased cervical anteversion and compensatory posterior extension of the upper cervical spine to maintain visual balance in the field of vision.