DOI: 10.1097/01.BRS.0000050418.20946.2E
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PMID: 12616170
Issn Print: 0362-2436
Publication Date: 2003/03/01
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Excerpt
Re: Pellisé F, Puig O, Rivas A, et al. Low fusion rate after L5–S1 laparoscopic anterior lumbar interbody fusion using twin stand-alone carbon fiber cages. Spine 2002;27:1665–1669.
I am writing to offer a perspective to the article by F. Pelliséet al2 regarding the rate of fusion with rectangular carbon fiber cages used for stand-alone laparoscopic fusion. This article reported 12 cases in which the average operative time was 237 minutes. The 2-year fusion rate was 16.6% according to CT scans. Clinical success was achieved in 11 of 12 patients (92%). Stability on flexion–extension radiographs was uniformly achieved, and if this were the accepted criterion for bony union, the apparent fusion rate would have been 100%.
Several years ago the DePuy AcroMed Corporation sponsored a pilot study of laparoscopic ALIF in 10 international centers using rectangular cages. Although the clinical results and structural stability were satisfactory, the fusion results were lower than optimum, and the study was abandoned. Although many of us desired to publish the results whatever they might be, insufficient data were provided by the investigators for a meaningful study.
Because of our experience, we prefer to do ALIF through a 5-cm anterior retroperitoneal approach, which can be completed in approximately 1 hour, using a large oval cage that provides better mechanical support and better bone graft surface area. Even with this construct, supplemental pedicle screw fixation may be required to achieve bony fusion at the desired rate of 95% to 98%.
Although the 12 patients in the Pellisé study do not represent a large enough study to determine a statistical fusion rate, the same reported results undoubtedly occur with the threaded metal screw-in cages, in which the actual bony union is more difficult to evaluate. Fraser and coworkers conducted a study of metal cylindrical cages in sheep and reported that “solid fusion through the cages did not occur—bony ‘locking’ with some growth through the holes but with intervening cartilaginous tissues remaining centrally, was the rule.”
Perhaps the “locked pseudarthrosis” described by Fraser 1 represents an adequate clinical result. The problem, of course, is that without solid bridging bone in a mechanically significant percentage of the fusion area, there may be long-term failure modes that are not apparent in a 2-year study.
Once again, the Pellisé study emphasizes the fact that flexion–extension radiographs are not adequate for documenting bony union.
