Influence of extending expansive open-door laminoplasty to C1 and C2 on cervical sagittal parameters

Background For patients with spinal canal stenosis in the upper cervical spine who undergo C3–7 laminoplasty alone, it remains impossible to achieve full decompression due to its limited range. This study explores the extension of expansive open-door laminoplasty (EODL) to C1 and C2 for the treatment of cervical spinal stenosis of the upper cervical spine and its effects on cervical sagittal parameters. Methods A retrospective analysis of 33 patients presenting with symptoms of cervical spondylosis myelopathy (CSM) and ossification in the posterior longitudinal ligament (OPLL) of the upper cervical spine from February 2013 to December 2015 was performed. Furthermore, the changes in the C0–2 Cobb angle, C1–2 Cobb angle, C2–7 Cobb angle, C2–7 SVA, and T1-Slope in lateral X-rays of the cervical spine were measured before, immediately after, and 1 year after the operation. JOA and NDI scores were used to evaluate spinal cord function. Results The C0–2 and C1–2 Cobb angles did not significantly increase ( P = 0.190 and P = 0.081), but the C2–7 Cobb angle ( P = 0.001), C2–7 SVA ( P < 0.001), and T1-Slope ( P < 0.001) significantly increased from preoperative to 1 year postoperative. In addition, C2–7 SVA was significantly correlated with the T1-Slope (Pearson = 0.376, P < 0.001) and C0–2 Cobb angle (Pearson = 0.287, P = 0.004), and the C2–7 SVA was negatively correlated with the C2–7 Cobb angle (Pearson = − 0.295, P < 0.001). The average preoperative and postoperative JOA scores were 8.3 ± 1.6 and 14.6 ± 1.4 points, respectively, indicating in a postoperative neurological improvement rate of approximately 91.6%. The average preoperative and final follow-up NDI scores were 12.62 ± 2.34 and 7.61 ± 1.23. Conclusions The sagittal parameters of patients who underwent EODL extended to C1 and C2 included loss of cervical curvature, increased cervical anteversion and compensatory posterior extension of the upper cervical spine to maintain visual balance in the field of vision. However, the changes in cervical spine parameters were far less substantial than the alarm thresholds reported in previous studies. We believe that EODL extended to C1 and C2 for the treatment of patients with spinal canal stenosis in the upper cervical spine is a feasible and safe procedure with excellent outcomes.