• I-Hsuan Chu, Abigail Faith Wu, Ling-Ya Chen, Jia-Yi Lin, Chia-Jung Hsu, Yi-Syue Tsou, and Jiann-Her Lin.
• Department of Neurosurgery, Taipei Medical University Hospital, Taipei, Taiwan; Taipei Neuroscience Institute, Taipei Medical University, Taipei, Taiwan.
• World Neurosurg. 2025 Feb 6: 123760123760.

ObjectiveThis study examines the risk of developing symptomatic retro-odontoid pseudotumor (ROP) following cervical laminoplasty. ROP can result in cervical myelopathy, leading to substantial morbidity. Identifying the risk factors for symptomatic ROP is essential to improving patient outcomes after laminoplasty.MethodsThe study included 2 symptomatic ROP patients and 2 additional cases from the literature, compared with a cohort of 57 non-ROP patients who underwent Hirabayashi open-door laminoplasty. Radiological assessments were conducted to evaluate cervical spine alignment, including MRI and postoperative dynamic radiographs. A novel index, the retro-odontoid soft tissue ratio (RS ratio), was introduced to quantify the extent of retro-odontoid soft tissue compression.ResultsThe study included 4 ROP patients (mean age: 68.5 years; all males) and 57 non-ROP patients (mean age: 65.7 years; 32 males, 25 females). The mean follow-up duration was 93.0 months (range: 48-156) for the ROP group and 32.5 months (range: 3-101) for the non-ROP group. The ROP group had significantly higher preoperative RS ratios (46.11 ± 4.80%) compared to the non-ROP group (30.29 ± 4.94%, p < 0.05). Post-operative cervical mobility assessment showed no significant difference in O-C2 contribution between the groups, with the ROP group at 59.82 ± 17.14% and the non-ROP group at 47.79 ± 14.17% (p = 0.13). The mean O-C7 range of motion (ROM) was lower in the ROP group (38.42 ± 16.23°) compared to the non-ROP group (49.69 ± 14.89°), but the difference was not statistically significant (p = 0.23). However, the change in O-C2 ROM was significantly different between the groups, with the ROP group showing an increase of +7.23 ± 4.70°, while the non-ROP group showed a decrease of -0.04 ± 9.90° (p < 0.05).ConclusionThis study highlights that a high preoperative RS ratio is a significant risk factor for symptomatic ROP, with a notable increase in O-C2 ROM observed in the ROP group following laminoplasty. These findings suggest that ROP is a progressive condition that may worsen after surgical intervention, particularly in patients with pre-existing retro-odontoid masses.Copyright © 2025 The Author(s). Published by Elsevier Inc. All rights reserved.

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