gms | German Medical Science

Objective: Autologous bone grafts were the first implants for interbody fusion and vertebral replacement for spondylodesis of the spine. In the last years, however, PEEK- or titanium-xenografts have become a standard for lumbar interbody fusion. However, there is no scientific evidence which proves that artificial implants are superior to autologous bone. During decompressive surgery in lumbar degenerative stenosis, autologous bone chips are removed which may be inserted into the intervertebral space for the induction of an osseous fusion if the insertion of a xenograft seems not possible. This retrospective analysis was performed to investigate whether lumbar interbody fusion using artificial cages was superior to autologous bone chips after posterior instrumentation.

Method: This retrospective analysis included 66 patients with degenerative lumbar one-level or two-level stenosis and spondylolisthesis. All patients had decompressive surgery and nucleotomy followed by posterior instrumentation and interbody fusion. If implantation of a bone-filled TLIF-cage could not be performed because the posterior edges of the vertebral end plates were too close even under forceful distraction, chips of spongious bone, removed during decompression, were inserted for induction of ossification. The clinical and radiological course was followed for at least 18 months assessing pain (VAS), functional outcome (ODI), osseous fusion rate and loosening of screws (CT).

Results: In 41 patients, bone-filled PEEK-cages were implanted (group 1), in 25 patients, spongious bone chips were used (group 2). No operative complication occurred during the insertion of cages or bone chips. The clinical outcome was comparable in both groups with a similar improvement of pain and functional outcome in both groups. After an observation period of 18 months, the fusion rate was 75% in group 1 and 90% in group 2. Loosening of one or more screws was observed in 12 of 41 patients in group 1 and in 3 of 25 patients in group 2. Spondylodiscitis occurred in 1 patient of group 2.

Conclusions: The results of this retrospective analysis are in favor of the implantation of spongious bone chips for lumbar interbody fusion in lumbar degenerative spondylolisthesis. The results suggest a randomized two-arm study which prospectively compares the two methods of interbody fusion.