Restoration and preservation of disc height and segmental lordosis with circumferential lumbar fusion: a retrospective analysis of cage versus bone graft.

Study Design: Retrospective radiographic analysis.

Objective: To determine whether restoration and preservation of (a) disc height and (b) segmental lordosis differ between patients treated with circumferential lumbar fusion using a bone graft or a cage for anterior support.

Summary Of Background Data: Restoration of disc height and lordosis is considered to be of crucial importance in circumferential fusion (CF). To determine whether restoration and preservation of disc height and segmental lordosis are dependent on the type of anterior support used, we compared the use of a cage with that of a bone graft in CF.

Methods: We retrospectively analyzed disc height and segmental lordosis in patients treated with primary lumbar monosegmental CF. The minimum period of follow-up was 9 months. A cage was used for anterior support in 23 patients and a bone graft in a further 23 patients. Disc height was determined on radiographs using an earlier introduced and validated distortion-compensated roentgen analysis, which was developed to compensate for distortion in central projection, off-center position, variation of stature, axial rotation, and lateral tilt of the spine.

Results: Disc height was restored in both groups but differences between preoperative and postoperative disc heights were significantly greater in the cage group (P=0.006). The cage also proved to be superior with regard to disc height preservation after follow-up (P=0.001). In addition, there was significantly less postoperative loss of segmental lordosis in the cage group (P=0.026).

Conclusions: The cage proved superior to the bone graft as anterior support in CF with respect to restoration/preservation of lordosis and disc height. However, no conclusions concerning clinical outcome or cost effectiveness can be drawn on the basis of this study.