• Cheng Li, Na Sun, Lei Li, Jingzhu Duan, and Yingkai Zhang.
• Department of Orthopaedic Surgery, Shengjing Hospital of China Medical University, Shenyang City, Liaoning Province, P.R. China.
• World Neurosurg. 2019 Jul 1; 127: e480-e487.

ObjectiveTo explore the feasibility and effectiveness of C1 lateral mass fixation via the posterior arch using pedicle screws of 3.5-mm diameter in patients whose atlas in the vertebral artery groove (C1 pedicle) was ≤3.5 mm in height.MethodsA total of 14 patients who underwent transposterior arch lateral mass screw fixation between 2014 and 2017 due to atlantoaxial instability were retrospectively studied. The height of the atlas pedicle was ≤3.5 mm on one or both sides. The position of the screw and damage of the screw trajectory were assessed using the postoperative 3-dimensional computed tomography. The patients were regularly followed up to observe the fracture union and bone graft fusion.ResultsIn total, 27 atlas pedicle heights were ≤3.5 mm and 22 screws were successfully inserted without any neurovascular complications. However, the pedicle wall was found to have a certain degree of damage with damaged superior/inferior wall in 4 of 6 pedicles respectively. Clinical symptoms were relieved to varying degrees, and patients demonstrated bony fusion during the postoperative follow-up.ConclusionsPedicle screws of 3.5-mm diameter could be fixed with a high success rate using the viscoelasticity and expansivity of the bone tissue even if the atlas pedicles were ≤3.5 mm in height. Although the screws had a certain probability of breaking the superior/inferior wall, they provided sufficient stability and enabled fracture or bone graft healing. Extraverted atlas pedicle screws should be considered in some cases.Copyright © 2019 Elsevier Inc. All rights reserved.

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