Correlation of PJK after TL/L posterior fusion and spinal-pelvic parameters in patients with Lenke type 5 AIS

Objective To analyze the risk factors of proximal junctional kyphosis(PJK)after TL/L posterior fusion in patients with Lenke type 5 adolescent idiopathic scoliosis(AIS). Methods Clinical data about 33 patients with Lenke type 5 AIS admitted to our department from March 2012 to December 2016 were retrospectively analyzed.Patients with a increasement of PJA>10.after surgery were assigned to PJK group,while others were in non-PJK group.The differences in spinal radiographic parameters including thoracic kyphosis(TK),thoracolumbar kyphosis(TLK),proximal junctional angle(PJA),lumbar lordosis(LL),lordosis in fusion(LIF),lordosis under fusion(LUF),sagittal vertical axis(SVA),pelvic incidence(PI),pelvic tilt(PT),sacral slope(SS),thoracolumbar/lumbar curve(TL/LC),thoracic curve(TC),pelvic incidence minus lumbar lordosis(PI-LL),etc.at pre-operation and last follow-up were analyzed,and the relationship of these parameters with occurrence of PJK was explored. Results There were 12 patients in PJK group with 3 males and 9 females and average age of 13.58±3.2 years old.Twenty-one patients were in non-PJK group with 5 males and 16 females and average age of 15.19±6.43 years old.No statistically significant difference was found in general information of both groups.In PJK group,there were significant differences in TK,PJA,LL,LIF,PI-LL,TL/LC,TC before operation and at last follow-up.And TK,TLK,LIF,TL/LC,TC showed significant differences before operation and at last followup in non-PJK group.TK,PJA,LL,PI-LL of both groups were significantly different at last follow-up.PJK was correlated with TK(r=0.805,P=0.000),TLK(r=0.397,P=0.022),LUF(r=-0.357,P=0.042),PI-LL(r=-0.528,P=0.002),LL(r=-0.364,P=0.037)respectively at the last follow-up. Conclusion Greater postoperative TK and LL maybe the potential risk factors of PJK after TL/L posterior fusion in patients with Lenke type 5 AIS.Intraoperative moderately decreasing TLK and correcting LL according to PI may decrease the risk of PJK after surgery.