Introduction: The incidence of kyphosis following cervical laminectomy is approximately 20% and is higher in patients with a straight spine. Despite the use of posterior instrumentation and arthrodesis after decompression, loss of lordosis or even the development of kyphosis remains prevalent. Inadequate cervical lordosis and other measures of sagittal cervical alignment have been shown to correlate with disability and general healthy scores, as well as myelopathy severity. The role of C2 in the posterior tension band, which maintains sagittal alignment, differs from the subaxial spine as it is the insertion point for erector spinae muscles that play a critical role in maintaining posture.

Methods: This study compares the radiographic outcomes of sagittal balance between two cohorts of patients who underwent posterior cervical decompression and fusion for cervical myelopathy over a 12 year period at a single institution. Demographic and surgical characteristics were collected using the electronic medical record for patients undergoing posterior cervical fusions including the axis (AF) and those that were subaxial fusions (SAF). Radiographic measurements included pre- and post-operative C2-C7 lordosis (CL), C2-C7 sagittal vertical axis (SVA), and T1 slope (T1S).

Results: After review of the electronic medical records, 229 patients were identified as having posterior cervical fusion and decompression for treatment of myelopathy. 167 patients had AF, while 62 had SAF. Posterior cervical fusion results in loss of CL in both cohorts. While there was no statistical difference in postoperative CL, there was a significant increase in SVA (p < 0.001) and T1S (p < 0.001) with AF.

Conclusions: Posterior cervical fusion is a procedure that results in loss of CL, and based on the results from this study, the inclusion of the C2 into the fusion construct also results in increased sagittal balance, increasing the SVA and T1S

Patient Care: The conclusions of this study suggest additional benefit of muscle preservation in posterior cervical fusion surgery for patients with cervical myelopathy, beyond what is already described in the literature. These results provide additional evidence showing that subaxial posterior cervical fusions maintain sagittal balance and alignment and fusion to C2 can, in some cases, be avoided.

Learning Objectives: To determine the impact that fusions including C2 have on radiographic parameters of cervical alignment in patients with cervical spondylotic myelopathy.

References: Kaptain GJ, Simmons NE, Replogle RE, Pobereskin L. Incidence and outcome of kyphotic deformity following laminectomy for cervical spondylotic myelopathy. J Neurosurg Spine. 2000;93(2):199-204. Hyun S-J, Kim K-J, Jahng T-A, Kim H-J. Clinical Impact of T1 Slope Minus Cervical Lordosis Following Multilevel Posterior Cervical Fusion Surgery. Spine . 2017:1. Shamji MF, Ames CP, Smith JS, Rhee JM, Chapman JR, Fehlings MG. Myelopathy and Spinal Deformity. Spine . 2013;38:S147-S148. Takeuchi K, Yokoyama T, Numasawa T, Itabashi T, Yamasaki Y, Kudo H. A novel posterior approach preserving three muscles inserted at C2 in multilevel cervical posterior decompression and fusion using C2 pedicle screws. Eur Spine J. November 2017. doi:10.1007/s00586-017-5402-2