RecruitingDevice studyClinical and Radiological Outcomes of Posterior Cervical Fusion Supplemented With Interfacet SpacersThis is a prospective study to assess fusion rates and cervical sagittal parameters following posterior cervical arthrodesis procedures supplemented with CIS. Data will be collected from medical records for up to 730 days after surgery. Data to be collected will be demographic, preoperative clinical information, surgical details, and radiographic information. Patients will also undergo a non-standard of care CT scan 2 years after surgery.