CORR Insights®: What Are the Patient-reported Outcomes, Complications, and Radiographic Results of Lumbar Fusion for Degenerative Spondylolisthesis in Patients Younger Than 50 Years?

Where Are We Now?

Although spondylolisthesis and stenosis are common, many controversies remain about how best to treat them. Several older studies reported better outcomes for decompression and fusion compared with decompression alone [1, 8, 11, 12]. But two recent publications in the New England Journal of Medicine suggest that decompression alone can result in comparable validated outcomes scores and functional parameters when compared with decompression and fusion [5, 7]. Several studies have compared pain, patient reported outcomes, and radiographic outcomes for various surgical techniques [2, 3, 4, 13, 15], but based on the data thus far, there are no clear advantages to any one technique.

In the current study, Goh and colleagues [6] conducted a retrospective analysis of longitudinally maintained registry data, specifically examining 2-year pain scores and patient reported outcomes of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) for symptomatic degenerative spondylolisthesis and stenosis in patients younger versus older than 50 years of age [6]. The authors were concerned that prior data [14] suggested worse satisfaction scores and patient reported outcomes in younger patients. It was reasonable of them to raise this concern, as that study [14] had a number of shortcomings that often come up in studies on this topic, including nonvalidated outcomes tools (such as “satisfaction” graded on a 1 to 4 scale, then further simplified to a dichotomous scale of yes/no), heterogeneity of patient presentations and inconsistent indications for the treatments used, and a lack of subgroup analysis.

This current study [6] highlights two important issues. First, while more common in an older population, symptomatic degenerative spondylolisthesis and stenosis in younger patients is not rare, and appropriate treatment algorithms to manage these conditions are necessary. And second, we continue to struggle to understand potentially prognostic variables that are associated with persistent pain and functional limitations following surgery for this disorder, because studies pool patients with “spondylolisthesis” together as though it is a single diagnosis, when in fact it really is a disease with a broad spectrum of severities and presentations. Even so, based on this study [6], surgeons should anticipate favorable improvements in pain and functional ability in appropriately selected younger patients with symptomatic degenerative spondylolisthesis and stenosis.

Where Do We Need To Go?

The fundamental problem is that spondylolisthesis and stenosis are studied as though they are one condition, when they really represent a spectrum of heterogeneous disorders with different clinical features such as radiculopathy, neurogenic claudication, mechanical back pain, and/or other types of nonmechanical complaints. They also vary in terms of pathoanatomic considerations like dynamic versus static spondylolisthesis, disc space height variability, location and nature of neural compression, and condition of adjacent segments. Age also is a variable, as Goh and colleagues show in their study [6]. Even something as basic as the best method for determining dynamic stability is still not clarified [9, 16]. Beyond this, medical conditions as well as socioeconomic factors are well known to play a role in patient-reported outcomes following surgery. All of these variables may impact postsurgical results, and so need to be studied further.

At this point, recognition of this heterogeneity is crucial. We need to identify the independent variables—which might include factors like age, preoperative functional status, psychosocial parameters, and radiographic elements—that may influence pain and patient-reported outcomes. Once identified, we can then systematically analyze the diverse cohorts of this heterogenous disorder and more accurately predict results for any given presentation of these conditions. New machine learning tools may help us analyze large sets of data efficiently and accurately.

We also must get a better understanding of instability. White and Panjabi defined instability as the loss of the ability of the spine under physiologic load to maintain intervertebral relationships such that there is no progression of pain, neurologic irritation or deficit, or spinal deformity [17]. Attempts to quantitatively define instability have been elusive. Translation of more than 3° is often considered unstable, but there is still uncertainty regarding evaluation and interpretation of stability [10]. A more-accurate assessment of stability will improve treatment decisions for this disorder

How Do We Get There?

The first step is to develop clinical predictors. While a randomized controlled trial would do this, post hoc analysis of prior randomized controlled trials or evaluation of registry data would be the most logical solution. A list of possible predictors such as those mentioned above (including clinical and radiographic parameters) could be evaluated statistically to help determine their role in predicting the success of surgery based on long-term pain, functional outcome scores, and reoperation rates. Initially, the main goal is to understand which parameters are predictive of success, and then more specifically, how they differentiate patients that do well with decompression alone versus decompression and fusion. These data will not only help better define clinical instability, but also other parameters that are important determinants for who benefits from decompression versus decompression and fusion.

With this information, the clinical and radiographic parameters that are relevant determinants of improvement with pain and function following surgery would be determined. Assuming decompression alone would be preferred if it is an adequate solution, this type of study could define those cohorts who should do well with decompression alone versus those who would need decompression and fusion. This is a big step.

From there, further prospective or retrospective evaluations of these cohorts could be done to get a better understanding of more granular information, including such things as value of minimally invasive surgery or the value of interbody fusion. In the end, this type of research would provide a guide for the least amount of surgery necessary to obtain the same functional outcome based on specific subgrouping or classification of these patients with degenerative spondylolisthesis.