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Friday, September 19, 2014

The biannual publication of “Evidence-Based Recommendations for Spine Surgery” is designed to review six recent potentially high impact papers. This month’s installment discusses articles that address questions that arise on a regular basis in a typical spine surgery practice. The first article reviewed was an RCT comparing TLIF to posterolateral instrumented fusion. The study reports no differences in outcomes or complications between the two procedures, though TLIF was associated with greater blood loss and longer operating room time. The major limitation of the article was the inclusion of essentially all fusion patients, regardless of diagnosis, number of levels fused, and revision status. Given the heterogeneity of the patient population, it is not surprising that few significant differences were noted. Most spine surgeons would agree that interbody fusion is not indicated in most cases of fusion, though it might improve outcomes in certain conditions such as a hypermobile isthmic spondylolisthesis, a focal scoliosis or a recurrent disk herniation requiring fusion. Future studies need to evaluate interbody fusion in specific diagnostic groups. The authors also reviewed a paper reporting a higher rate of cancer in patients undergoing fusion using a high-dose BMP-2  formulation compared to those undergoing fusion with autograft, but the numbers are small, cancer is poorly defined, and many of the included cancers were skin cancers. The recent AOSpine North America study on myelopathy was reviewed, and this large cohort study did demonstrate improvement with surgery for patients across the myelopathy severity spectrum. Unfortunately, we still do not know if patients with mild myelopathy benefit from surgery compared to non-operative treatment or if surgery is worth the risk in elderly, debilitated patients with severe symptoms. Another interesting study compared outcomes between patients undergoing an L4-5 posterior interbody fusion for disk pathology in whom the L3-4 interspinous complex was removed or left intact. The authors reported higher rates of adjacent segment degeneration and re-operation for adjacent segment disease in those who had the L3-4 interspinous complex taken down.  This study supports preserving as much normal anatomy as possible while sufficiently decompressing the neural elements. A Swedish study looked at predictors of success following ACDF and found that non-smokers, men, and those with the highest baseline neck pain scores improved the most. Unfortunately, these groups are also the ones most likely to improve with non-operative treatment, so studies looking at surgical outcome predictors are not that helpful if a non-operative arm is not included. Finally, a definitive RCT looking at bracing for adolescent idiopathic scoliosis did show a clinically and statistically significant benefit, a finding that supports a widespread practice.

 

Reviews such as this are instructive, both in the sense they inform practice when good evidence is available as well as making it clear when evidence does not exist and the best clinical course is ambiguous. Of these six articles that were reviewed, the scoliosis trial was the only one that led to a definitive conclusion about the best treatment, and bracing for scoliosis is already widely accepted. This study’s impact is similar to the Spine Patient Outcomes Research Trial (SPORT) in that both provide strong evidence to support currently accepted practice. The other studies provide some insight to questions that remain unanswered such as the “best” lumbar fusion technique or how to treat patients with mild myelopathy. Critical review of these studies makes it clear that the literature is giving us a sense of the best way to treat the average degenerative spondylolisthesis patient or the average myelopathy patient, but the “average” patient never walks into clinic. In order for research to have more of an impact on clinical decision making, future studies will need to evaluate predictors of outcomes based on both patient- and disease-specific characteristics. Given that treatment decisions always involve at least two options (i.e. surgical and non-operative), future work will need to look at predictors of outcomes for all of the treatments under consideration.

 

Please read this installment of Evidence-Based Recommendations for Spine Surgery. Let us know how these recommendations change your view of these topics by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, September 12, 2014

Fusion for degenerative spondylolisthesis (DS) has been widely accepted since the classic 1991 article by Herkowitz and Kurz that demonstrated the superiority of decompression and fusion compared to decompression alone for this diagnosis.1 That study reported the results of uninstrumented fusion, and since that time instrumented and interbody techniques have been widely adopted without any convincing evidence that the addition of instrumentation improves clinical outcomes.2 Instrumentation clearly does improve fusion rates, though it remains unclear if this translates to improved patient-reported outcomes. In order to assess trends in fusion technique for DS, Dr. Kepler and his colleagues from Philadelphia analyzed the American Board of Orthopaedic Surgery (ABOS) Part II board examination database to evaluate trends in fusion technique for DS from 1999-2011. This database includes the self-reported six month case logs of orthopaedic surgeons sitting for the examination as candidates for board certification. From 1999-2011, the number of DS cases submitted per candidate more than doubled. Uninstrumented fusion was performed in 36% of cases in 1999 and fell to 8% of cases in 2011. Instrumented posterolateral fusion varied from 35% in 1999 to 65% in 2003 to 40% in 2011. This trend was mirrored by the increasing use of interbody fusion, which was performed in only 14% of cases in 1999 yet became nearly as common as instrumnted posterolateral fusion by 2011, in which 37% of cases included interbody fusion. Analysis of regional variation in fusion techniques yielded interesting data demonstrating that Northwest surgeons used interbody fusion in 41% of cases compared to only 18% in the Southeast and 22% in the Northeast. Candidate-reported outcomes and complications were similar across all fusion techniques, with over 90% of outcomes classified as good or excellent and specific complication rates generally below 5%.

 

The ABOS database is extremely useful for identifying trends over time as it provides a six-month snapshot into the practice of a large number of early-career surgeons. The rapid adoption of instrumented and interbody fusion for DS without any strong literature support is striking but also consistent with the general trends in the adoption of new technology by the spine surgery community. While this study suggests that interbody fusion was nearly as common as instrumented posterolateral fusion in 2011, the actual rate of interbody fusion by the spine community may be even higher given that candidates were aware that they were collecting cases for the boards, and they may have been more conservative in their decision-making during the case collection period. This study was a nice demonstration of the increased rate of interbody fusion over the first decade of the millennium, though limitations of the database preclude any meaningful conclusions about outcomes and complications. Prior studies have yielded conflicting results about the association between fusion technique and complications, with some suggesting increased complications with interbody fusion and others reporting no differences.2,3 Cost is clearly increased by the use of more extensive instrumentation.4 This study serves as an illustrative case study on the adoption of technology in spine surgery prior to the establishment of evidence supporting its use. This topic is begging for an RCT to determine the most effective fusion technique for DS, which likely varies with patient and disease characteristics that have yet to be defined.  

 

Please read Dr. Kepler’s article on this topic in the September 1 issue. Do these findings change your thoughts on fusion technique for DS? Let us know by leaving a comment on The Spine Blog.


Adam Pearson, MD, MS

Associate Web Editor

 

REFERENCES

1.            Herkowitz HN, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis. The Journal of bone and joint surgery 1991;73:802-8.

2.            Abdu WA, Lurie JD, Spratt KF, et al. Degenerative spondylolisthesis: does fusion method influence outcome? Four-year results of the spine patient outcomes research trial. Spine (Phila Pa 1976) 2009;34:2351-60.

3.            Maghout Juratli S, Franklin GM, Mirza SK, Wickizer TM, Fulton-Kehoe D. Lumbar fusion outcomes in Washington State workers' compensation. Spine (Phila Pa 1976) 2006;31:2715-23.

4.            Tosteson AN, Tosteson TD, Lurie JD, et al. Comparative effectiveness evidence from the spine patient outcomes research trial: surgical versus nonoperative care for spinal stenosis, degenerative spondylolisthesis, and intervertebral disc herniation. Spine 2011;36:2061-8.

 


Friday, September 05, 2014

Orthopaedic surgeons (OS) and neurosurgeons (NS) have both traditionally performed spine surgery. As spine surgery developed, OS typically performed fusions and scoliosis surgery, while NS traditionally performed decompressions and more cervical spine surgery. In modern spine surgery, OS and NS tend to perform the same procedures, with a few exceptions (i.e. OS tends to perform most adolescent idiopathic scoliosis surgery, while most intradural surgery is performed by NS). Given the different training backgrounds of the two specialties, Dr. Seicean and colleagues from Cleveland used the National Surgery Quality Improvement Program (NSQIP) database to explore differences in patient characteristics, diagnoses, procedures, and outcomes between the two specialties. They included over 50,000 patients who underwent spine surgery from 2006-2012 and found that NS peformed about 2/3 of the cases. OS tended to perform more fusions, more multilevel, multi-code procedures, and more surgery for degenerative disk disease. In the unadjusted analysis, the authors report that OS was associated with a higher rate of prolonged length of stay (LOS, defined as the top quartile of LOS or greater than 4 days), and over twice the transfusion rate (11.1% vs. 4.6%). After propensity score matching for diagnosis and procedure (apparently defined as fusion, laminectomy or laminectomy + fusion), two groups with over 17,000 patients were compared. This analysis demonstrated that OS patients had a 20% increased odds of prolonged LOS and still had twice the odds of receiving a post-operative transfusion. Other captured outcomes such as complications, readmissions, and re-operations were not significantly different.

 

While database studies such as these frequently demonstrate differences, they rarely explain the causes underlying the differences. This is one of those studies. Any number of hypotheses could be generated to explain the observed differences, though this study design precludes hypothesis testing. It is possible that differences in training results in OS keeping patients in the hospital longer and being more enthusiastic about transfusions, though this seems unlikely. More likely is the possibility that the limited number of variables on which patients were matched—vague ICD-9 diagnosis codes and apparently a limited number of procedural variables—resulted in unmeasured confounders that drove the differences. While the authors should have been able to match on factors like location of surgery (cervical vs. lumbar vs. thoracic), primary vs. revision surgery, and anterior vs. posterior vs. AP surgery, it is not clear these factors were taken into account. Even after matching, OS still performed 5% more multilevel procedures. If the NS cohort included more cervical procedures while the OS cohort included more lumbar cases, one would expect longer LOS and more transfusions due to that alone. Additionally, if OS tended to perform more deformity cases with long constructs and this was considered in the same category as a two level fusion (i.e. “multilevel surgery”), this would also result in longer LOS and a higher transfusion rate. While the question under investigation is interesting, it is unclear if the current analysis provides any meaningful answers. It is likely that a much more detailed analysis than is possible with the NSQIP database would be required.

 

Please read Dr. Seicean’s article on this topic in the September 1 issue. Does this article change how you view differences between orthopaedic surgeons and neurosurgeons performing spine surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, August 29, 2014

Obesity is a well-known risk factor for complications following spine surgery. However, obesity is associated with other comorbidities such as diabetes and heart disease that also contribute to complications. In an effort to determine if obesity is an independent risk factor for adverse events after spine surgery, Dr. Seicean and her colleagues from Cleveland used the NSQIP database to analyze about 50,000 patients who underwent spine surgery between 2006 and 2012. They compared rates of adverse outcomes (i.e. major and minor complications, prolonged length of stay, return to OR, discharge to nursing facility, readmission, and mortality) that occurred within 30 days among patients stratified by BMI. Not surprisingly, they found that most adverse events occurred more frequently in obese patients, and the rate of adverse events increased with increasing degrees of obesity. Patients with a BMI over 40 were nearly twice as likely to have a complication compared to patients with a BMI less than 25. They also performed a propensity-score matched analysis in order to control for the effect of comorbidities and found that obesity tended to be an independent risk factor for adverse events only in the morbidly obese (BMI > 40). This indicates that while overweight and mildly obese patients did have an increased risk of adverse events, these differences were likely being driven by comorbidities like diabetes.

 

This is an interesting study in that it clearly demonstrates that obese patients, especially morbidly obese patients, are at increased risk for complications, but obesity-related comorbidities may be more important than obesity itself. The results need to be considered in light of the limitations inherent in a NSQIP database study, including possible coding inaccuracies, the lack of patient reported outcomes, and a limited, 30 day follow-up period. The most concerning limitation is the inability of the authors to determine exactly what type of procedure was performed. The authors did not control for invasiveness or location of surgery, and it is possible that selection bias played a role, with morbidly obese patients undergoing less invasive procedures. Obesity is likely a more important risk factor in extensive posterior lumbar surgery compared to anterior cervical surgery. This study adds to the body of literature indicating that obesity is a risk factor for adverse events following surgery, and this information should be communicated to obese patients as they make decisions about treatment. Morbidly obese patients should be well-informed about their high risk for suffering a complication if they elect to undergo spine surgery. Additionally, it suggests that “healthy” patients with mild obesity without comorbidities like diabetes, hypertension, and heart disease may not be at significantly increased risk for complications, which can also help to guide treatment decisions.

 

Please read Dr. Seicean’s article on this topic in the August 15 issue. Does this change how you see the relationship between obesity and complications after spine surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, August 22, 2014

Treatment decision-making can be challenging in some cases of cervical spondylotic myelopathy (CSM). The spine community agrees that surgery is indicated in the case of a healthy, middle-aged patient with clinically significant myelopathy. However, there is scant data to guide treatment in patients with mild signs and symptoms, and the natural history of mild myelopathy is unknown. Choosing treatment for the frail, elderly patient with severe disease is also challenging as the benefits may not justify the substantial risks of extensive surgery. Given these difficulties in deciding whether to perform surgery for myelopathy, efforts have been made to determine if demographic, clinical, or radiographic characteristics can predict outcomes after surgery. In the August 15 issue, Dr. Fehlings and his colleagues from Toronto analyzed the associations between MRI findings and baseline and post-operative disease severity in 134 CSM patients. Transverse area (TA) of the spinal cord at the level of maximum compression as well as the presence of intramedullary T2 hyperintensity and/or T1 hypointensity were determined. These were correlated with physical exam findings, mJOA scores, Nurick grade, SF-36 scores, and timed walking test. The investigators found that there were moderate correlations between TA and physical exam findings, Nurick grade, and mJOA scores, both pre- and post-operatively. Correlations between intramedullary cord signal changes and disease characteristics were much weaker and generally not statistically significant. Interestingly, neither TA or cord signal changes were associated with change scores, indicating that patients with severe cord compression and signal changes could still have significant improvement with surgery.

 

This study is helpful in that indicates that the degree of cord compression is fairly well-correlated with the clinical severity of myelopathy. It should serve as a reminder to the spine physician to be suspicious of the diagnosis of CSM in patients with pronounced findings and mild cord compression on MRI. It does not shed much light on the prognostic role of cord signal change as the study found minimal correlation between cord signal change and disease severity or degree of improvement. Such a result could be due to a true lack of correlation in the study population or represent a Type II error due to lack of power. Some prior studies have suggested that cord signal changes were associated with less post-operative improvement, though that finding has not been consistent. While studies such as this one provide some prognostic information to spine surgeons and patients about what to expect post-operatively, the lack of a non-operative cohort limits how much it can assist with surgical decision-making. For patients struggling with the decision about whether or not to undergo surgery, prognostic models need to be able predict both surgical and non-operative outcomes in order to determine the likely benefit of surgery. Studies that could provide these data are difficult to perform as most spine surgeons feel patients with a diagnosis of CSM should be treated surgically, so there is a lack of equipoise to perform a randomized clinical trial. The best option going forward is probably an observational study in which patients who are felt to be surgical candidates yet decline surgery are followed to get a better sense of the natural history of CSM using modern outcome measures. Until such a study is performed, patients and spine surgeons are left with predictive data from only one side of the treatment decision-making equation.

 

Please read Dr. Fehlings’s article on this topic in the August 15 issue. Does this change how you see the prognostic role of MRI findings in CSM? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD,MS

Associate Web Editor

About the Blog

Spine Journal
This Blog provides a forum for discussion about high impact articles published in Spine, including the bi-annual publication of "Evidenced-Based Recommendations for Spine Surgery." Website users can use this forum to discuss how the articles have affected their practice and query the authors about their findings and recommendations.