Motion trumps fusion at NASS debate

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The treatment of many common spinal conditions by procedures designed to preserve motion or by the more conventional fusion was the subject of a series of debates at the 30th Annual Meeting of the North American Spine Society (NASS; 14–17 October, Chicago, USA), chaired by Scott Blumenthal of the Texas Back Institute, Plano, USA.

Pierce D Nunley (Spine Institute of Louisiana, Shreveport, USA) and Jean-Jacques Abitbol (California Spine Group, San Diego, USA) were given the task of debating the treatment of a case of two-level cervical herniated nucleus pulposes either with an anterior cervical discectomy and fusion (ACF) procedure or with total disc replacement.

The case involved a 30-year-old male patient with a two-level herniated disc at C4–5 and C5–6, who had experienced symptoms including pain in both arms and the neck for over five years. The patient displayed radiculopathy, and had failed non-operative treatment. Imaging revealed no significant deformity.

Speaking first, Abitbol argued the case for the fusion procedure. Citing more than 60 years of good results, he contended that it offers predictable results. This fusion procedure, however, has been associated with a significant incidence of adjacent segment pathology, he admits. To win the debate, he argues, total disc replacement would have to offer something better than the tried-and-tested ACF. Citing a 2008 The Spine Journal study by Auerbach et al, Abitbol expressed concern about the high rate (57%) of absolute contraindications for total disc replacement reported. All of the 167 patients included in the study could have been treated with ACF.

The purported advantage of disc replacement is to preserve motion at the operated segment, Abitbol claimed. Consistent results in the literature show minimal differences in pain and disability scores, with significantly lower rates of reoperation, as well as higher rates of neurological success.

However, Abitbol argued that these results may be confounded by the US Food and Drug definition of neurological success commonly used by authors, which may not reflect clinically significant success. Abitbol then noted that no prospective randomised studies have confirmed or denied that adjacent segment disease following disc replacement is lower than with ACF. A 2010 paper co-authored by Nunley (Jawahar et al, The Spine Journal), he asserts, actually shows an equivalent risk of developing the disease postoperatively in both procedures. Lumbar degenerative disc disease was found to be a significant risk factor in this paper, and others. It is unclear in the literature, he argues, whether the restricted motion associated with fusion is a cause of adjacent segment disease, or whether it is the result of natural progressive degeneration. The promise of total disc replacement, he concludes, is not borne out in variable results collected variously from radiographic and clinical findings.

Responding to Abitbol’s use of his own data, Nunley began his argument by contending that Abitbol had failed to take into account the differences in data for one- and two-level procedures. This data comprises the only US level 1 results on cervical total disc replacement at two levels. By narrowing the results down to two-level only, Nunley showed that in fact, they support disc replacement as a better option than ACF in the 330 remaining patients (225 treated by disc replacement, 105 by ACF). Significant benefits were found for total disc replacement over 60 months in neck disability index, patient satisfaction and rates of reoperation. Notably, the rate of subsequent surgeries was significantly higher from 24 months (3% vs. 11.4% for ACF) through to 60 months (4% vs. 16.2%). Nunley agreed that results in the literature had been confusing regarding the measurement of adjacent segment disease. But, in these data, the radiographic results were so favourable towards total disc replacement that he argued they must be considered. Five-year rates of adjacent segment disease surgery were cited in response to Abitbol’s questioning of the ability to link the disease ACF procedures, which showed a dramatic difference in the rates for each procedure (3.4% vs. 11.4% in favour of disc replacement).

Nunley presented further support for his position with data showing disc replacement to offer greater quality-of-life benefits at a lower cost than ACF for two-level procedures. Noting new recommendations from ISASS supporting disc replacement as a “viable alternative” to ACF, Nunley concluded that total cervical disc replacement was not simply a new gold standard in the treatment of two-level disc herniation, but a platinum standard.

At the end of the debate, the audience voted in favour of total disc replacement surgery over treatment by anterior cervical discectomy and fusion.

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