Importance of preserving the C7 spinous process and attached nuchal ligament in French-door laminoplasty to reduce postoperative axial symptoms.

A comparative clinical trial was conducted to clarify the importance of preserving the C7 spinous process and attached nuchal ligament for the reduction of the axial symptoms after French-door laminoplasty in cervical spondylotic myelopathy patients. Forty-one cervical spondylotic myelopathy patients were enrolled. French-door laminoplasty from C3 to C7 in 22 patients (group 1), and from C3 to C6 in 19 patients (group 2) was performed. The whole structure of the C7 spinous process and the attached nuchal ligament were preserved in group 2. The pre- and post-operative evaluation regarding severity of clinical symptoms was assessed using the Japanese Orthopaedic Association (JOA) score. Pre-operative and subjective outcome regarding axial symptoms were also assessed using a visual analog pain scale questionnaire (VAS: 10-0, where a higher score indicates greater pain) at 1- and 2-year follow-up. Non-parametric testing (Mann-Whitney's U test) was used to establish differences between the two groups for categorical data (P < 0.05). There was no significant difference between the two groups in pre- and post-operative JOA score. The mean VAS was 5.6 +/- 1.4 in group 1, 5.4 +/- 1.7 in group 2 pre-operatively, and 6.4 +/- 1.7 in group 1 and 2.4 +/- 1.9 in group 2 at 1-year follow-up. The mean VAS score at 2-year follow-up exhibited 6.2 +/- 1.9 in Group 1, 2.3 +/- 1.8 in group 2. There was no significant difference in VAS between the two groups before surgery (P = 0.506), but significant differences were noticed at 1-year and 2-year follow-up (P < 0.05), indicating the presence of significantly fewer post-operative axial symptoms in group 2. Laminoplasty of the entire C7 structure is not necessary to obtain satisfactory recovery based on JOA score. Preservation of the C7 spinous process and the attached nuchal ligamentous structures is important to reduce post-laminoplasty axial symptoms.