Long-term outcome data following spine surgery are hard to come by, and long-term non-operative outcomes are virtually non-existent. The Spine Patient Outcomes Research Trial (SPORT) received NIH funding for eight years of follow-up for degenerative spondylolisthesis (DS) patients treated with surgery or non-operative treatment. Over 600 patients enrolled, and approximately half agreed to be randomized to surgery or non-operative care. Twenty-eight percent of patients randomized to surgery did not undergo surgery, while 54% of those randomized to non-operative care did have surgery. This high level of treatment non-adherence prevented meaningful analysis of the RCT on an intent-to-treat basis. As such, the randomized and observational cohorts were combined in an as-treated analysis that was statistically controlled for potential confounders. The follow-up rate at 8 years was 56%, and this loss to follow-up had some potential to bias the results. In the as-treated analysis, surgery had a significant advantage compared to non-operative treatment, and this difference remained significant out to eight years. The surgery patients improved approximately 10 points more on the Oswestry Disability Index at 8 years. Similar differences were observed on the SF-36 and other outcome measures. In a subgroup analysis, there were effectively no significant outcome differences among those treated with an uninstrumented fusion, pedicle screw instrumentation, and pedicle screws plus an interbody device. At eight years, the reoperation rate was 22% and did not differ significantly across fusion techniques.
The SPORT produced some of the highest quality data available to the spine community. Despite this, significant limitations such as crossover and loss to follow-up have potentially biased the results. Nonetheless, the data are consistent across eight years of study and seem to match clinical experience. There has been significant controversy about the best surgical technique to treat DS, with ongoing debate about the most effective type of fusion1 as well as about whether fusion is even necessary.2,3 The results of the current study do not offer much new information on the topic and are limited by the fact that patients were not randomized to different fusion technique. As a result, the patients were significantly different at baseline, and, despite controlling for these differences, it is hard to know if confounders affected the outcome. A prior observational study suggested the results of uninstrumented fusion could degrade over time due to a high rate of pseudarthrosis, though this was not observed in SPORT.4 Fusion technique did not affect reoperation rate either. While the different techniques have specific advantages and disadvantages, these do not seem to affect long-term patient reported outcomes or reoperation rate. Similar to the long-term SPORT studies on spinal stenosis and disk herniation, the current study demonstrated the long-term advantage of surgery compared to non-operative treatment for DS. The best operation for DS remains unknown, and it likely depends on patient and disease characteristics. Now that most would agree that surgery leads to better long-term outcomes than non-operative treatment, hopefully future studies can help surgeons select the best surgical technique for individual patients.
Please read Dr. Abdu's article on this topic in the December 1 issue. Does this article change how you consider long-term outcomes for DS patients? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor
1. Baker JF, Errico TJ, Kim Y, Razi A. Degenerative spondylolisthesis: contemporary review of the role of interbody fusion. Eur J Orthop Surg Traumatol 2017;27:169-80.
2. Forsth P, Olafsson G, Carlsson T, et al. A Randomized, Controlled Trial of Fusion Surgery for Lumbar Spinal Stenosis. N Engl J Med 2016;374:1413-23.
3. Ghogawala Z, Dziura J, Butler WE, et al. Laminectomy plus Fusion versus Laminectomy Alone for Lumbar Spondylolisthesis. N Engl J Med 2016;374:1424-34.
4. Kornblum MB, Fischgrund JS, Herkowitz HN, Abraham DA, Berkower DL, Ditkoff JS. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective long-term study comparing fusion and pseudarthrosis. Spine 2004;29:726-33; discussion 33-4.