Letter to the Editor regarding “Application of Zero-profile Spacer in the Treatment of Three-level Cervical Spondylotic Myelopathy – 5 year Follow-up Results” by Sun et al

I commend the work of Sun et al1 for their retrospective study elaborating on the 5-year follow-up results of anterior cervical decompression and fusion (ACDF) with zero-profile spacer (ZP) and anterior plate with cage (PC) for patients with cervical spondylotic myelopathy. However, I would like to address some concerns related to their follow-up results. Although it was noted from the results that radiographic Adjacent Segment Degeneration (ASDeg) was noted in 10 levels in PC group and only one level in ZP group, what concerns the surgeon is the number of patients who developed a clinical adjacent segment disease (ASD) out of those radiographic ASDeg noted. With a 2% increase in the incidence per year following surgery, ASDs remains a significant contributor to reoperation rates after spinal arthrodesis.2,3 According to the authors, none of the ASDeg required reoperations but did any of those ASDeg in PC group developed new symptoms of radiculopathy or myelopathy which required nonoperative treatment remains unanswered. Authors have warned the surgeons for the usage of ZP for three-level ACDF for significant loss of sagittal correction and disc height compared to PC despite giving similar neurological outcomes. But authors did not highlight the significant ASDeg noted in the PC group which might result in ASDs requiring reoperations in the future.