Effect of postoperative lordosis distribution index on adjacent segment disease after L4-5 posterior lumbar interbody fusion

Objective To investigate the relationship between postoperative lordosis distribution index (LDI) and adjacent segment disease (ASD) after L4-5 posterior lumbar interbody fusion (PLIF) for spinal degenerative disease. Methods Totally 266 subjects who underwent L4-5 PLIF in our center for spinal degenerative disease from 2009 to 2014 were included in our study.The average follow-up time was 85 months.Lower lumbar lordosis (LLL),lumbar lordosis (LL) and LDI on the pre-and postoperative radiograph were measured.Perioperative information,comorbidities and operative data were documented.Logistic regression analysis was used to identify the risk factors of ASD.Kaplan-Meier curve was plotted for the comparisons of ASD-free survival of 3 different postoperative LDI subgroups. Results The incidence of ASD was 7.5%.For every 1-unit increase in BMI,adjacent segment disease risk increased by 25%.Patients with abnormal postoperative LDI had a 5.45 times higher risk of ASD than patients with normal postoperative LDI.Kaplan-Meier curves showed a marked difference in ASD-free survival in low and high LDI subgroups compared to moderate LDI group (71.43% and 78.30 vs 90.95%,P<0.05,respectively). Conclusion Higher BMI and abnormal postoperative LDI are risk factors of ASD.Patients with abnormal postoperative LDI are more likely to develop ASD than those who had normal postoperative LDI.