Background: Corpectomy is a surgical intervention that involves resecting part or all of a vertebral body to alleviate pressure on neural structures. This procedure is typically indicated in patients with degenerative spinal disorders, neoplasms, or trauma. We report a rare case involving a male patient who underwent a C4–C5 corpectomy and cervical stabilization using a C5–C6 3D expandable cage. The patient suffered from extensive cervical spine degeneration secondary to rheumatoid arthritis, accompanied by cervical myelopathy and osteoporosis. Imaging revealed critical spinal canal stenosis, highlighting a high risk for tetraplegia. This report illustrates a surgical approach that effectively managed the pathological features, emphasizing the importance of individualized surgical planning and interdisciplinary collaboration for optimal outcomes.