Sagittal segmental alignment as predictor of adjacent-level degeneration after a cloward procedure

The Cloward anterior interbody fusion is commonly performed for cervical disc herniation or spondylosis. In followup studies, various authors have noted clinically relevant adjacent-level degeneration. However, factors associated with adjacent-level degeneration are not well known.

We asked whether the postoperative sagittal segmental alignment of the fused vertebrae could be used as a predictor of adjacent-level degeneration.

We retrospectively studied 107 patients, aged 35 to 55 years, with one-level cervical disc disease between C4 and C7 operated on from 1985 to 1995 by discectomy and one-level anterior cervical fusion according to the Cloward procedure. In standard radiographs of the cervical spine in lateral view, the alignment of the involved intervertebral space (sagittal segmental alignment) and the sagittal alignment of the cervical spine were measured and the adjacent-level degeneration was assessed using the Kellgren and Lawrence criteria. The minimum followup was 10 years (mean, 16 years; range, 10-23 years).

Preoperatively, mean sagittal segmental alignment was 0.6°±2.0° and sagittal alignment of the cervical spine was 17.0°±4.9°. At last followup, the mean sagittal segmental alignment was 1.8°±4.1° and mean sagittal alignment of the cervical spine was 19.7°±6.6°. Adjacent-level degeneration was present in 60% of cases with postoperative sagittal segmental alignment of 0° or less and in 27% of cases with postoperative sagittal segmental alignment of more than 0°.

To prevent adjacent-level degeneration, we recommend proper lordotic sagittal segmental alignment when anterior interbody fusion of the cervical spine is indicated.

Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.