[Radiographic comparison of anterior cervical fusion after two-level discectomy or single-level corpectomy for two-level cervical spondylotic myelopathy]

To compare the pre- and post-operative radiographic data of a single-level anterior cervical corpectomy and fusion (ACCF)or a two-level anterior cervical discectomy and fusion (ACDF) for patients with two-level cervical spondylotic myelopathy.We retrospectively reviewed the lateral cervical radiographs of 110 patients undergoing a single-level ACCF or a two-level ACDF for the treatment of cervical myelopathy from March 2005 to May 2008. All of them underwent anterior cervical fusion using poly ether ether ketone (PEEK) cage or titanium meshes packed with autogenous bone and fixed-screw titanium plate fixation. A single-level ACCF (group of ACCF, n = 48) or a two-level ACDF (group of ACDF, n = 62) was performed. The following parameters were analyzed: cervical sagittal alignment, Cobb angles of fusion segments, graft collapse, adjacent-segmental degeneration and rate of bone fusion.During a follow-up period of 24 - 60 months, no significant differences existed in sagittal alignment, adjacent-segmental degeneration and rate of bone fusion between two groups. Graft subsidence and loss of Cobb angles of fusion occurred significantly more during the first 2 months post-operation than after 2 months in each group (P0.01). However, the group of ACCF subsided and lost more than the group of ACDF (P0.05). Caudal endplate subsidence significantly progressed after the first 2 months in the Group of ACCF (P0.05).Graft subsidence and loss of fusion segmental lordosis of two groups occur mainly in an early post-operation stage (first 2 months). The group of ACDF with PEEK cage is superior to the group of ACCF with titanium meshes in maintaining the height and lordosis of fusion segments. Single-level ACCF with titanium meshes continues subsiding at the caudal endplate of fusion segments even after 2 months.