Randomized Controlled Trial: Comparison of Radiological and Axial Pain Outcome Between C3-6 Open Door Laminoplasty and C3 Laminectomy With Cervical Laminoplasty
Phase: NA
Conditions: Myelopathy Cervical, Kyphosis Post Surgical, Neck Pain, Ossification of Posterior Longitudinal Ligament, Cervical Spondylosis With Myelopathy
Sponsor: Seoul National University Hospital

 
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Title: Randomized Controlled Trial Comparing Clinical and Radiological Outcomes 
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Between C3 Laminectomy with C4-C6 Laminoplasty and C3-C6 Laminoplasty 
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Study protocol (date: 2017-01-05) 
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Background 
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C3 laminectomy in cervical laminoplasty is a modified laminoplasty technique that can 
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preserve semispinalis cervicis muscle attached to the C2 spinous process. Several previous 
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studies have shown that this technique can lead to better outcomes of postoperative axial neck 
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pain and C2-C3 range of motion (ROM) than conventional cervical laminoplasty. However, 
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there is still a lack of understanding of total and proportional postoperative cervical sagittal 
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alignment outcomes. 
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Study design 
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A randomized clinical trial will be conducted on patients with cervical laminoplasty for 
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treating CSM or OPLL at a single tertiary referral university hospital. Patients will be 
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randomly assigned to either the LN group (C4-6 laminoplasty with C3 laminectomy) or the 
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LP group (C3-6 laminoplasty) at a 1:1 ratio. The sample size will be calculated to achieve a 
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target of 80% power with a two-tailed significance level of 0.05, with a medium effect size 
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(Cohen's d = 0.50), resulting in 63 patients per each group. The trial will enrolled consecutive 
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patients who underwent cervical laminoplasty from March 2017. Participants' ages will 
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ranged from 20 to 80 years. Patients with metastatic tumors, combined fractures, or previous 
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posterior cervical surgeries will be excluded from this study. Patients with a diagnosis of 
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CSM or OPLL will be assessed prior to randomization by a neurosurgical specialist through a 
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combination of history-taking, clinical examination, and radiological workup, including 
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dynamic radiographs and cervical spine computer tomography (CT) or magnetic resonance 
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image (MRI) scans. Diagnosis of CSM will be based on symptoms of myelopathy and 
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stenosis at two or more cervical levels on MRI. Diagnosis of OPLL will be made based on 
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CT findings. The randomization process, surgical group options, and required follow-up 
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evaluations and imaging will be fully explained to eligible patients by a neurosurgical 
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specialist. After obtaining informed consent, patients will be randomized using a computer-
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generated block design in 1:1 ratio with concealed assignment managed by an independent 
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research nurse. The attending surgeons, patients, and staff members in the operating room 
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will be blinded to the surgical method until the day of surgery. A concealed paper indicating 
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the patient's assigned group will be provided in the operating room, and the surgeon will 
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verify the patient's group just before commencing the surgery. This study was approved by 
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the hospital's Institutional Review Board (IRB number: H-1610-136-804).  
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Data collection and outcomes 
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Data will be collected using patient-reported outcome questionnaires and plain x-rays taken at 
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the outpatient clinic before surgery and at 1, 2, and 3 years postoperatively. Patients will 
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record their outcomes directly without assistance of the surgeon or other study participants. 
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Radiological parameters will be assessed using 150% magnified images by one of the authors 
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(a fellow). Three measurements will be performed, and the median value will be selected as 
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the final measurement. The measurements will be conducted utilizing the measuring tools 
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within the institution's Picture Archiving and Communication System (M6, Infinitt 
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Healthcare, Seoul, Korea) operating on a Microsoft Windows environment (Microsoft Corp., 
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Redmond, WA, USA). We selected C2-C7 Cobb angle (C2-C7 CA) as the primary outcome 
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measure, considering the importance of postoperative kyphotic changes in cervical 
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laminoplasty, which have been associated with long-term recurrent myelopathy and chronic 
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neck pain. Additionally, we chose the Neck Disability Index (NDI) as another primary 
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outcome measure to evaluate axial neck pain, as it is commonly acknowledged as a potential 
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advantage of C3 laminectomy. Secondary outcome measures included other radiologic 
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parameters such as C2-C3 Cobb angle (C2-C3 CA), C4-C7 Cobb angle (C4-C7 CA), cervical 
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sagittal vertical axis (cSVA), T1 slope (T1S) and T1 slope minus cervical lordosis (T1S-CL), 
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as well as presence of C2-C3 interlaminar fusion. Other clinical outcomes, such as numerical 
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rating scores for neck (NRS-N) and limb (NRS-L) and the Euro-Quality of Life-5 Dimension 
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(EQ-5D), will be also assessed. We will examine operation-related factors, including open 
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side, presence of dome-like laminectomy at the C2 or C7 level, operative time, estimated 
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blood loss, and complications such as hinge fracture, neural injury, dural injury, and wound 
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infection. 
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Statistical analysis plan 
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Outcomes will be analyzed using the modified intention-to-treat (mITT) strategy. The mITT 
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population will consist of all participants with randomly assigned surgery and have available 
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at least a year of postoperative data from 1 to 3 years. Baseline and operation-related 
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characteristics of the LN and LP groups will be compared using independent t-tests for 
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continuous variables, and chi-square tests or Fisher's exact tests for categorical variables. 
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Postoperative clinical outcomes and radiological parameters will be compared between 
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groups and over time using linear mixed-effects models, with fixed effects including 
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preoperative values of tested variables, group, time, interaction between group and time, 
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other factors with possible relation with outcomes such as age, BMI and disease, and a 
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random effect of subjects. Least squares mean for postoperative clinical outcomes and 
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radiological parameters will be estimated. Comparisons will be made between the treatment 
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groups. For variables with a significant difference in the interaction between time and group, 
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post-hoc analysis will be performed for each time point and adjusted p-values will be 
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evaluated using the Bonferroni method. All data will be analyzed using SPSS software 
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version 27.0 (SPSS, Chicago, IL, USA), with statistical significance defined at p < 0.05 (two-
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sided). 
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