Background  Laminoplasty is the preferred treatment for multilevel cervical spondylotic myelopathy, and current studies have focused on modified procedures that preserve muscle attachment into C2 and/or C7 spinous. However, the existing studies are retrospective or prospective non-randomized studies with low level of evidences.

  Objective  To compare the clinical outcomes of modified cervical double-door laminoplasty with preservation of muscle insertions into C2 and C7 spinous process (modified surgery group) versus conventional C3-C7 cervical double-door laminoplasty (conventional surgery group) in the treatment of multilevel cervical spondylotic myelopathy.

  Methods  A single-center, single-blind, prospective, randomized controlled trial was conducted. Patients with multilevel cervical spondylotic myelopathy admitted to Beijing Shijitan Hospital were recruited from January to December in 2019. The patients were randomly assigned in a 1:1 ratio, to undergo conventional laminoplasty or modified laminoplasty. The primary outcomes were the change of JOA score from baseline to one-year follow-up and the neurological recovery rate. Secondary outcomes included changes in VAS score and NDI score, and operation-related outcomes included length of procedure, blood loss, quantity of postoperative drainage, length of postoperative stay, as well as changes in cervical range of motion (ROM) and C2-C7 Cobb angle. The postoperative complications of the two groups were compared, including axial symptoms (AS) and C5 palsy related to laminoplasty, as well as other common complications in spinal surgery.

  Results  In this study, 82 participants were randomly assigned to the conventional surgery group or modified surgery group, 73 participants completed at least one-year post-baseline follow-up and were included in this analysis (37 patients in the conventional surgery group and 36 patients in the modified surgery group), including 44 males and 29 females, with an average age of 60.47 years. Baseline data of the two groups were balanced, with no statistically significant difference (P>0.05). No significant differences were observed between the two groups in the changes in JOA score ( \bar x95% CI : 3.863.41, 4.32 vs 3.783.22, 4.34) and the neurological recovery rate ( \bar x95% CI : 59.83%54.14%, 65.53% vs 55.66%49.83%, 61.48%). However, compared with the conventional surgery group, the VAS ( \bar x95% CI: -2.54-2.84, -2.24 vs -3.22-3.59, 2.85, P=0.005) and NDI scores ( \bar x95% CI: -13.46-16.18, -10.74 vs -19.50-24.05, -14.95, P=0.023) of patients in the modified surgery group decreased significantly. The blood loss (439.46±155.28 mL vs 350.84±171.95 mL, P=0.024) and length of stay after operation (13.24±6.87 d vs 10.47±4.26 d, P=0.043) in the modified surgery group were significantly less than those in the conventional surgery group. Furthermore, the changes in ROM (-4.53±5.83° vs -8.61±6.28°, P=0.005), C2-C7 Cobb angel (-2.16±6.88° vs -6.52±8.65°, P=0.020) in the modified surgery group were significantly less than those in the conventional surgery group. Eleven (32.35%) patients in the conventional surgery group and 3 (9.38%) patients in the modified surgery group were newly diagnosed with AS after operation in one year, with statistically significant difference (P=0.034).

  Conclusion   In this study, a prospective randomized controlled trial is conducted to manifest that the modified double-door laminoplasty with preservation of muscle insertions into C2 and C7 spinous process can achieve similar cervical cords decompression and neurological recovery compared with the conventional C3-C7 double-door laminoplasty, at the same time, the modified surgery is better to maintain cervical ROM and physiological curvature, and it can alleviate postoperative neck pain and reduce the incidence of AS.