Observations of resorption of the posterior lateral bone graft in combined anterior and posterior lumbar fusion.

The past 10 years have seen the development of a surgical reconstructive procedure for the treatment of patients disabled with severe postlaminectomy syndrome. The technique involves anterior lumbar fusion, replacing the excised disc with bone graft, and under the same anesthetic, applying a posterolateral bone graft along with segmental instrumentation. The purpose of this report was to compare cases with fused and nonfused posterolateral grafts in cases where the anterior fusion was successful. Seventy-four interbody segments in 30 patients were fused while 47% (14 of 30) of the posterolateral bone grafts underwent resorption. Both allograft and autograft were used and this did not appear to influence the resorption seen at the 4-year follow-up period. The most likely factor to explain resorption of the posterolateral graft is deprivation of the proper mechanical forces in the lateral gutter by the simultaneous use of anterior lumbar interbody grafts.