• Jong-Myung Jung, Seung-Jae Hyun, Ki-Jeong Kim, Tae-Ahn Jahng, Hyun-Jib Kim, and Yunhee Choi.
• Department of Neurosurgery, Spine Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea.
• World Neurosurg. 2019 Sep 1; 129: e522-e529.

BackgroundThis study aimed to investigate the risk of proximal junction kyphosis (PJK) and proximal junction failure (PJF) associated with screw trajectory (straightforward vs. mixed vs. anatomic) at upper instrumented vertebra (UIV).MethodsA single-center, single-surgeon consecutive series of adult patients who underwent lumbar fusion for ≥4 levels (the UIV of the thoracolumbar spine, T9-L2, and the lower instrumented vertebra at the sacrum or pelvis) was retrospectively reviewed. Patients were divided into 3 groups according to UIV screw trajectory: group S, 2 straightforward screws; group M, 1 straightforward screw and 1 anatomic trajectory screw; and group A, 2 anatomic trajectory screws.ResultsA total of 83 patients were included in this study, including 51 in group S, 16 in group M, and 16 in group A. The incidence of PJK in group S (12 patients, 23.5%), group M (7 patients, 43.8%), and group A (9 patients, 56.3%) significantly increased in sequence by group (P = 0.044). Anatomic trajectory screw fixation increased the risk for PJF requiring revision surgery compared with straightforward screw fixation (3 patients [18.8%] vs. 1 patient [2.0%]; P = 0.040). Multivariable analysis identified that anatomic trajectory screw fixation was a significant risk factor for PJK (P = 0.008; adjusted odds ratio = 7.591; 95% confidence interval, 1.69-34.093).ConclusionAnatomic trajectory screw fixation at the UIV is a substantial risk factor for PJK and PJF. To reduce PJK and PJF, straightforward screw fixation at the UIV is recommended in adult spinal deformity correction surgery.Copyright © 2019 Elsevier Inc. All rights reserved.

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