RESUMO
Objective: To investigate the role of minimally invasive crenel lateral lumbar interbody fusion (CLIF) in the decision of fusion level in posterior correction for severe adult degenerative scoliosis. Methods: This is a prospective study.Patients with level Ⅴ and Ⅵ of Lenke-Silva classification who were treated at Department of Orthopedics,the Second Affiliated Hospital, School of Medicine, Zhejiang University from June 2016 to March 2019 were included.First,the enrolled patients completed the preoperative clinical and imaging examination,the Lenke-Silva classification was evaluated,the surgical segments in first-stage CLIF was determined and the fusion segments required for single-stage posterior correction was predicted.After the first-stage CLIF,patients received reassessment of Lenke-Silva classification and global coronal and sagittal balance.Patients were divided into two groups:the effective group (level of Lenke-Silva classification decreased) and the ineffective group (level of Lenke-Silva classification unchanged).Second-stage posterior surgery was performed based on the results of reassessments.The fusion segment,Cobb angle,parameters of global coronal and sagittal plane,visual analogue pain score (VAS) and Oswestry disability index (ODI) were compared between the two groups preoperatively,after first-stage CLIF,second-stage posterior fixation and at the final follow-up.The potential factors associated with the decrease of the level of Lenke-Silva classification were recorded and compared between the two groups.Independent sample t test,repeated measure analysis of variance,rank sum test,χ2 test or Fisher exact method were used to compare the difference among groups. Results: Fifty-four patients were enrolled,including 8 males and 46 females,aged (68.8±5.8) years (range:56 to 77 years).Preoperatively,26 patients were classified as level Ⅴ by Lenke-Silva classification,28 cases were grade Ⅵ.CLIF was performed in 194 segments,with 114 segments(58.8%) receiving anterior column realignment (ACR) and 15 segments(7.7%) using hyperlordotic cages.After first-stage CLIF,22 patients with level Ⅴ and 10 patients with Ⅵ of Lenke-Silva classification decreased and were classified into effective group.The level of the remaining 4 patients with level Ⅴ and 18 patients with grade Ⅵ unchanged and were classified into ineffective group.Preoperatively,the apical vertebrae was below L1 in all 32 patients of effective group and 18 (81.8%,18/22) patients of ineffective group.The difference was statistically significant (P=0.023).There were 7 (31.8%,7/22) patients had continuous osteophyte in front of the intervertebral space in ineffective group,while none patient had continuous osteophyte in front of the intervertebral space in effective group,and the difference was statistically significant (P=0.001).In first-stage CLIF,more intraoperative ACR(71.2% vs.39.5%,χ²=20.660,P<0.01)and hyperlordotic cage (12.7% vs.0,P=0.001) were used in the effective group,while there was less severe cage subsidence after the operation (5.9% vs.15.8%,χ²=4.793,P=0.029) in effective group.After first-stage CLIF,there was no difference in the Cobb angle between the two groups.While,lumbar lordosis (LL) in effective group (34.0±8.3)° was greater than that of the ineffective group (25.5±9.7)° (t=3.478,P=0.001),and the difference between the pelvic incidence (PI) and LL in effective group (15.7±4.6)°was significantly smaller than ineffective group(20.0±10.8)° (t=-2.129,P=0.038).The posterior fusion levels was less,the rate of fusion to thoracic spine region and the actual fusion segment was less than that of single-stage posterior correction in effective group (all P<0.01).All patients were follow-up for 24 to 45 months.There was no significant difference in radiological and clinical results between the two groups after first-,second-stage surgery and at the final follow-up (all P>0.05). Conclusions: First-stage CLIF decreased the Lenke-Silva classification of some patients with severe degenerative scoliosis.Combined with the reassessment of Lenke-Silva classification and global coronal and sagittal plane,it helps to accurately determine the fusion segment.Decrease of Lenke-Silva classification is associated with the preoperative level of apical vertebrae,continuous osteophytes in front of the intervertebral space,intraoperative use of ACR and hyperlordotic cage and the degree of cage subsidence postoperatively.