Abstract: Objective To investigate the risk factors of proximal junctional kyphosis (PJK) after posterior long segmental lumbar fusion for degenerative lumbar disease. Methods From October, 2012 to July, 2014, 118 degenerative lumbar disease patients who accepted posterior long segmental fusion and followed up at least 1.5 years were reviewed. All the PJK were evaluated with X-ray. Results Sixty-six patients completed the follow-up (mean of 3.2 years), in which 12 patients with PJK (PJK group), and the others without (non-PJK group, n=54). There was significant difference in body mass index, bone density and the last Oswestry Disability Index scores (t>2.194, P<0.05) between both groups, as well as the rate of the upper instrumented vertebra (UIV) located in the thoracolumbar segment (T₁₁-L₁) (χ²=4.63, P<0.05). The PJK angle was more in PJK group than non-PJK group pre-surgery, post-surgery and finally (t>3.862, P<0.001). Binary Logistic regression showed that osteoporosis (OR=5.328, 95% CI: 1.110~25.581), UIV located in the thoracolumbar segment (T₁₁-L₁) (OR=6.239, 95% CI: 1.157~33.648) and the pre-surgery PJK angle >10° (OR=5.789, 95% CI: 1.075~31.183) were the independent risk factors of PJK. Conclusion Osteoporosis, UIV located in the thoracolumbar segment (T₁₁-L₁) and the pre-surgery PJK angle >10° are risk factors of PJK after posterior long segmental lumbar fusion.

Key words: degenerative lumbar spinal disease, proximal junctional kyphosis, posterior long segmental lumbar fusion, risk factors