Impact Of Different Laminae Open Angles On Axial Symptoms After Expansive Open-door Laminoplasty

Objective: Axial symptoms are frequently encountered complication after laminoplasty.Some studies have reported the influencing factors and preventive measures of axial symptoms after laminoplasty.However,impact of different laminae open angles on the postoperative axial symptoms remains unclear.The objective of the current study was to explore the effect of different laminae open angles on postoperative axial symptoms and to discuss the possible mechanisms of the impact of different open angles on axial symptoms.Methods: We retrospectively analyzed 124 patients with multilevel cervical compression myelopathy with or without developmental cervical stenosis who were treated with expansive open-door laminoplasty from February 2012 to January 2015.The operational level ranged from C3-C7 in all patients.The laminae open angles at the C4,C5 and C6 levels were measured after operative 1 week.The mean value was taken for statistical analysis.The average lamina open angles is 40.2°±11.3°,range from 20° to 69°.The patients were divided into 2 groups,group A(open angles<40 degrees,71 patients including 44 males and 27 females)and group B(open angles≥40 degrees,53 patients including 32 males and 21 females).All patients completed at least 2-year follow-up.The incidence of axial symptoms and Visual Analogue Scale(VAS)score were recorded preoperatively,2 weeks postoperatively,6 months and the final follow-up.C2–7 Cobb angle,range of cervical motion(ROM),Japanese Orthopedic Association score(JOA)were compared between 2 groups.Results: There were no significant differences between the 2 groups in sex,age,diagnosis,blood loss,operation time,duration of disease,and duration of follow-up(P >0.05).The JOA score in group A improved significantly from 9.0±1.5 before the surgery to 13.6±1.2 at the final follow-up,the JOA score in group B improved from 8.8±1.5 before the surgery to 13.3±1.4 at the final follow-up.The recovery rate was 58.6%±11.7% and 56.6%±10.8% in group A and group B.No significant difference was found in preoperative JOA scores,postoperative JOA scores and recovery rate between group A and group B(P>0.05).Both groups gained significant JOA improvement postoperatively(P<0.05).Preoperative and postoperative C2–C7Cobb angle and ROM comparisons were significantly different(P<0.05)in both groups.There were no significant difference for other clinical and radiography parameters between the groups(P>0.05).At 2 week after operation,there were 24 patients in group A(33.8%)and 31 in group B(58.5%)complained of severe postoperative neck pain,The mean VAS was 2.7 ±1.8 in group A and 3.5±1.9 in the B group,the difference was significant(p<0.05).At 6 months,there were 12 patients in group A(16.9%,VAS,1.8±1.4)and 18 patients in group B(34%,VAS,1.8±1.4),which was statistically significant(p< 0.05).At final follow-up,there were 5 patients in the group A(7.0%,VAS,1.4±0.8)and 7 patients in the group B(13.2%,VAS,1.6±1.1),the difference between the 2 groups was not statistically significant(P>0.05).Postoperative complications: 2 patients(2.8%)in group A and 7 patients in group B,(13.2%)have C5 nerve root palsy after surgery.1 patient in group A and 1 patient in group B have superficial wound dehiscence.Cerebrospinal fluid leakage,epidural hematoma and laminar re-closure were not found in both groups.Conclusion: When the lamina open-door angles are between 20 and 40 degrees,there are not only ensure adequate spinal cord decompression but reduces the incidence of early and midterm postoperative axial symptoms and C5 nerve root paralysis.