Friday, October 25, 2019
Less invasive decompression vs. decompression and fusion for degenerative spondylolisthesis
With conflicting evidence about the benefit of fusion in addition to decompression for lumbar degenerative spondylolisthesis (DS), surgeons are left to using their judgment about the "stability" of the listhetic segment while choosing the appropriate surgical technique. The general consensus is that adding a fusion to the decompression will decrease the likelihood of a repeat operation at the index level but increase the morbidity of the procedure and the need for a reoperation at an adjacent level. It remains unclear if patients are better-off treated with a smaller operation associated with an increased risk of a technically challenging reoperation at the same level or with a larger operation with an increased risk of a straightforward reoperation for adjacent segment disease. Some papers have suggested an increased risk slip progression and reoperation with laminectomy alone, which has prompted surgeons to explore less disruptive non-fusion surgical techniques such as unilateral laminotomy with bilateral decompression (ULBD). In an effort to better understand how ULBD compares to the traditional posterolateral decompression and fusion (PLDF), Dr. Kuo and colleagues from Kaiser Permanente in California performed a retrospective cohort study comparing 5-year reoperation rate between DS patients treated with ULBD and PLDF. They identified 164 ULBD patients and then propensity-score matched them with 437 PLDF patients based on age, sex, race, and smoking status. Not surprisingly, the two groups had very similar demographic characteristics. There were non-significant trends towards a higher proportion of women (71% vs. 64%) and a lower proportion of normal weight patients (28% vs. 33%) in the PLDF group. The ULBD group was also more likely to undergo a multiple level decompression (63% vs. 36%). The 5-year reoperation rate was 10% in the ULBD group compared to 17% in the PLDF group. Nearly all (94%) of the reoperations in the ULBD group involved the index level, while only 32% did in the PLDF cohort. The majority of reoperations in each group involved a fusion.
This paper does a nice job summarizing the Kaiser Permanente group's experience with ULBD for DS and demonstrated a lower 5-year reoperation rate after ULBD compared to traditional PLDF. As the authors point out, it is important to recognize that this is not a randomized study, so confounding by unmeasured variables likely affected the results. Overall, only 4% of the DS patients treated surgically underwent ULBD, so this cohort represents a highly selected group. While the authors matched for basic demographic characteristics, the surgeons likely selected patients for ULBD based on other unmeasured factors such as the perceived stability of the listhetic level and location and severity of stenosis. As such, the two groups were probably quite different at baseline in ways this study did not measure. Additionally, patient reported outcomes were not measured, so it is unclear if patients had similar results from the two procedures, independent of the reoperation rate. The PLDF group also had a nearly 3-fold higher rate of reoperation in the first 90 days, which was likely driven by a higher rate of surgical site infection. This study was performed prior to the widespread adoption of intra-wound vancomycin powder, so the reoperation rate in the PLDF group was likely higher in this study compared to what would be seen today. Based on these data, one can reasonably conclude that the 5-year reoperation rate may be somewhat lower in a well-selected cohort of patients treated with ULBD compared to PLDF. However, it is unclear what proportion of DS patients are appropriate for ULBD and how surgeons can identify these patients. Additionally, patients and surgeons need to decide if they would prefer a reoperation at the index or adjacent level, and most surgeons would likely suggest that outcomes are better and complications are less frequent with adjacent level surgery. It may be that a slightly higher reoperation rate is acceptable if complicated revision surgery at the index level can be avoided. The real question raised by this paper is how to select patients for ULBD. That is not an easy question to answer, and to do so would likely require either a very large RCT comparing ULBD to PLDF or an even larger database of DS patients undergoing surgery with relatively long-term follow-up. Degenerative spondylolisthesis includes a very broad spectrum of pathology, and future research is needed to identify factors that can help the surgeon select the right operation for each individual patient.
Please read Dr. Kuo's article on this topic in the November 1 issue. Does this change how you view the use of ULBD in DS? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor