The Spine Blog

Friday, July 21, 2017

The high rate of mechanical failure, revision surgery, and complications following adult spinal deformity (ASD) surgery is well-documented in the spine literature. Increasing age, 3 column osteotomy (3CO), and large changes in alignment are known risk factors for mechanical failure. While most authors have advocated correcting sagittal alignment parameters to as close to “normal” as possible, there is not strong literature indicating that achieving “normal” alignment is protective against mechanical failure. To better understand risk factors for mechanical failure following ASD surgery, Dr. Hallagher and colleagues from Denmark analyzed data from 138 ASD surgery patients with a mean follow-up of 4 years to determine risk factors for mechanical failure. They defined mechanical failure as revision surgery for pseudarthrosis, hardware failure, junctional kyphosis or fracture. The average age was 61, 70% of patients were female, the average fusion length was 10 levels, 71% were fused to the sacrum or pelvis, 44% had 3CO, and no BMP was used. Overall, 47% of patients underwent revision surgery for mechanical failure, with survival analysis suggesting a 5 year mechanical failure rate of 56%. Significant risk factors for failure included 3CO (OR=1.7), lowest instrumented vertebra L5 or S1 (OR=6.6), iliac fixation (OR=2.2), SVA change > 8 cm (OR=1.9), thoracic kyphosis > 40 degrees preoperatively (OR=2.0) or 50 degrees post-operatively (OR=2.4), increase in lumbar lordosis > 30 degrees (OR=1.9), or postoperative sacral slope < 30 degrees (OR=2.3). Achieving “normal” sagittal parameters did not protect against mechanical failure, and, if anything, was associated with a trend towards greater risk of failure.

The authors should be congratulated for putting together a large series of ASD patients and presenting honest results that show a high rate of mechanical failure. This paper adds to the literature suggesting that aggressive correction of deformity in the older population—especially with the use of 3CO—is associated with a high rate of mechanical failure. In this series, achieving “normal” sagittal alignment did not prevent mechanical failure, and the literature addressing this is mixed. Like all observational studies, this series has limitations that need to be considered when interpreting the results. The patient population was very heterogeneous, including typical, older adult deformity patients with kyphoscoliosis as well as younger patients who were likely being treated for idiopathic scoliosis. The authors also did not report on the rates of different kinds of mechanical failure, with junctional kyphosis being lumped together with pseudarthrosis. Additionally, no BMP was used, and it has been shown that BMP-2 use can reduce the rate of pseudarthrosis in long thoracolumbar fusions to the pelvis. Despite these limitations, this paper—and others—strongly suggest that aggressive correction of sagittal imbalance is associated with a high rate of mechanical failure. This is not surprising, given that these deformities are longstanding and are associated with contraction of soft-tissues on the ventral aspect of the spine and weakness of the extensor musculature. While osteotomies can correct the bony malalignment, they don’t address the soft tissue issues. As a result, strong deforming forces remain that push the spine back towards its original, malaligned state. These forces can result in mechanical failure either within the fusion construct or at the proximal junctional level. Data seems to be accruing to suggest that aggressive correction of sagittal imbalance in the older patient increases the mechanical failure rate, yet undercorrection may result in worse patient reported outcomes. This leaves the deformity surgeon in the difficult position of trying to find a balance between “normal” sagittal alignment and just enough correction to improve outcomes while minimizing risk for mechanical failure.

Please read Dr. Hallagher’s article on this topic in the July 15 issue. Does this change your view of aggressive correction of sagittal imbalance in the older adult deformity patient? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Saturday, July 15, 2017

Whether to perform a fusion along with a revision discectomy when treating a recurrent disk herniation remains a controversial decision in spine surgery. While authors have suggested theoretical benefits to fusion, there is scant literature supporting this practice. Most studies have suggested that most patients do fairly well with a revision discectomy without a fusion, though outcomes are probably not as quite as good as the primary surgery, and there may be a higher complication rate.1 There is no literature on this topic in the workers’ compensation (WC) population, so Dr. O’Donnell and colleagues from Cleveland analyzed the Ohio Bureau of Workers’ Compensation database to compare outcomes between recurrent disc herniation patients treated with revision discectomy (RD) and revision discectomy and fusion (RDF). Of over 10,000 WC patients diagnosed with a lumbar disc herniation between 2005 and 2012, they identified 298 who underwent single level RD (n=102) or RDF (n=196). The two groups were similar at baseline, though the RDF group had a significantly higher rate of legal representation (92% vs. 82%) and a trend towards a higher proportion with psychological comorbidities (14% vs. 7%) and preoperative opioid use (51% vs. 39%). The authors found that the RD patients returned to work (RTW) at a significantly higher rate than the RDF patients (40% vs. 27%), used opioids for a significantly shorter period of time (409 vs. 661 days), and had approximately $35,000 less in medical bills. Logistic regression analysis revealed that psychiatric comorbidities, using opioids following reoperation, and having a fusion were all independent predictors of not returning to work.

The authors have done a nice job adding a new finding to the WC literature, and the results of this study are in-line with their findings in previous studies that have demonstrated low RTW rates in WC patients undergoing fusion. The WC population has notoriously poor outcomes, and the 27% RTW rate in this young, healthy population undergoing RDF is no exception. The 40% RTW rate in the RD cohort is far from stellar, though it is significantly better than the RDF group. There are clear limitations to a retrospective cohort study based on an administrative database like this one, namely that unmeasured confounders could be contributing to some of the observed differences in RTW rate between the two groups. Another major limitation is a lack of patient reported outcome measures, so we do not know if symptom severity was different at baseline or post-operatively. Return to work typically does not correlate well with pain or function in the WC population, so RTW cannot be used as a surrogate for these other outcomes.2 The authors admit that these data do not provide strong evidence regarding the indications for a fusion accompanying revision discectomy. However, it is clear that the addition of a fusion did not improve RTW rates in the WC population, and performing a fusion may have contributed to worse RTW rates. The addition of a fusion to a revision discectomy may be appropriate for certain recurrent herniation patients, though the literature does not make it clear how to identify these patients, and the majority of recurrent disk herniation patients will likely do equally as well or better with a revision discectomy alone.


Please read Dr. O’Connell’s article on this topic in the July 15 issue. Does this change how you consider the role of fusion for recurrent disc herniation in the workers’ compensation population? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

REFERENCES

1.            Abdu RW, Abdu WA, Pearson AM, Zhao W, Lurie JD, Weinstein JN. Reoperation for Recurrent Intervertebral Disc Herniation in the Spine Patient Outcomes Research Trial: Analysis of Rate, Risk Factors, and Outcome. Spine (Phila Pa 1976) 2017;42:1106-14.

2.            Atlas SJ, Tosteson TD, Blood EA, Skinner JS, Pransky GS, Weinstein JN. The impact of workers' compensation on outcomes of surgical and nonoperative therapy for patients with a lumbar disc herniation: SPORT. Spine (Phila Pa 1976) 2010;35:89-97.

 


Friday, July 7, 2017

Low back pain (LBP) is an incredibly common condition that is frequently treated outside of compliance with evidence-based treatment guidelines. Many professional societies and health systems have created treatment guidelines for acute LBP over the past two decades. Most of the guidelines focus on ruling out red flag conditions (i.e. cancer, infection, cauda equine syndrome) and then recommending that patients stay active, take basic analgesics, and avoid imaging unless symptoms persist. While guidelines abound, it is unclear if they actually change practice patterns, and compliance with many guidelines frequently remains low. In order to assess compliance with treatment guidelines for 22 different conditions in Australia, the CareTrack study was initiated. This study was a random population sample based on the phone book, and it identified 164 patients who had sought treatment for LBP and whose providers were willing to provide their medical records for audit by a team of research nurses. The medical records were reviewed for compliance with 10 treatment guidelines similar to those adopted by the National Health and Medical Research Council of Australia. These guidelines included ruling out red flags, performing a history and physical exam including a neurological exam, and avoiding ineffective treatments such as steroids, TENS, traction, and bed rest. Analysis of compliance was stratified across GPs, allied health professionals (i.e. chiropractors, physical therapists), specialists (i.e. orthopedists and rheumatologists), and hospital providers. Overall compliance with the guidelines was 72%, ranging from 41% for assessment of infection to 98% for not recommending bed rest. Allied health professionals and hospital providers had the highest compliance rates, while GPs and specialists had the lowest. Only 4 specialist practices were evaluated, so data on this group may not have been representative.

This study demonstrated a moderate degree of compliance with treatment guidelines and is consistent with prior literature on the topic. While compliance with recommendations to rule out red flags was relatively low, especially for GPs and specialists, the analysis focused on documentation of these pertinent negative findings. It is possible that these doctors queried patients about red flags but simply did not document the negative findings in the record. Another significant limitation of this study is that many practices did not provide their records, which potentially introduces selection bias. It would have also been interesting to evaluate compliance with recommendations about imaging and the use of steroid injections, but these topics were not addressed in the guidelines. This study adds to the literature suggesting that the mere publication of guidelines may not have much of an effect on practice patterns. It also identified specific topics and provider groups that can be targeted for education. Changing practice behaviors is complex, and education about guidelines may be ineffective. Other approaches such as embedding the guidelines in the electronic medical record (i.e. templated notes and order sets for different conditions that prompt providers to comply) or creating pay for performance schemes to incentivize compliance have been considered, but there is scant data on the effectiveness of these approaches.

Please read Dr. Runciman’s article on this topic in the July 1 issue. Does this change how you view compliance with guidelines for the treatment of LBP? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, June 30, 2017

Intraoperative neuromonitoring has been shown to be effective in detecting injury to the neural elements during deformity correction, and, in many cases, intraoperative maneuvers can be performed to prevent the development of a permanent neurologic deficit. As such, the use of neuromonitoring has become the standard of care for deformity surgery. However, the utility of neuromonitoring—specifically EMG—for detecting nerve root injury during lumbar pedicle screw placement is not well established. Given the lack of data supporting the use of intraoperative EMG during lumbar screw placement, Dr. Ajiboye and colleagues from Los Angeles used the PearlDiver database to analyze trends in EMG use during instrumented posterolateral lumbar fusion as well as the rate of post-operative neurological deficit among patients who were monitored or not monitored with EMG. They identified nearly 10,000 patients undergoing instrumented lumbar fusion for degenerative conditions (interbody fusion cases were excluded), with intraoperative EMG used in 25% of cases. They found that the rate of EMG use increased from 15% in 2007 to 29% in 2009 and then declined to 22% in 2015. Intraoperative EMG was used most frequently in the South (30%) and least frequently in the Midwest (17%). Post-operative neurological injury within 30 day of surgery was 1.3% in both the monitored and unmonitored groups.

While large database studies based on billing data frequently have significant limitations that preclude strong, clinically relevant conclusions, they do provide a good snapshot of service utilization over time. This study does a nice job demonstrating the adoption of neuromonitoring for routine instrumented lumbar fusion in the late 2000s followed by a decline in popularity in the 2010s. The study did not detect a difference in post-operative neurological deficit between the monitored and unmonitored groups, though the limitations of the study need to be considered before drawing strong conclusions about the utility of intraoperative EMG. The most significant limitation is the likely inconsistent coding of post-operative neurological injury. Surgeons may be vague about documenting such events due to medicolegal concerns, and thus coders may not be aware of the injury or may choose not to code for it. Additionally, the type and timing of injury is not captured in the coding, and many of these events may have nothing to do with pedicle screw placement. That being said, the reported rates of post-operative neurological injury are in line with other studies, and may represent a reasonable estimate of the injury rates. The motivation for using intraoperative EMG varies and includes both medicolegal reasons and the belief that its use could reduce the rate of neurological injury. The spine community seems to be losing enthusiasm for this type of monitoring, possibly due to a changing medicolegal landscape, increased surgeon experience with the technology that can be cumbersome and frequently ineffective, or a growing literature questioning its utility. Intraoperative neuromonitoring clearly has a role in complex deformity surgery, though its effectiveness in more routine lumbar fusion remains to be seen.

Please read Dr. Ajiboye’s article on this topic in the July 1 issue. Does this change how you view the use of intraoperative EMG for routine instrumented posterolateral lumbar fusion? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor


Friday, June 23, 2017

Laminoplasty (LP) is an attractive treatment option for myelopathy in the setting of ossification of the posterior longitudinal ligament (OPLL). A posterior approach avoids the risk of durotomy associated with anterior procedures, and LP has a lower perioperative complication rate compared to the more invasive laminectomy and fusion (LF). Additionally, adjacent segment degeneration is less common with the non-fusion procedure. Potential downsides of LP include increased neck pain, kyphosis, and OPLL progression. There is little data on the rates of OPLL progression following LP compared to fusion procedures, so Dr. Lee and colleagues from Korea performed a meta-analysis comparing OPLL progression and neurological decline between laminoplasty and fusion procedures (including both anterior and posterior fusions). They identified 11 studies including 530 patients, 6 of which were laminoplasty case series and the other 5 included various combinations of LP and fusion patients. They calculated an OPLL progression rate of 65% in the LP group compared to 8% in the fusion group, a statistically significant difference. They also found that the rate of progression increased with time. The meta-analysis demonstrated an 8.3% rate of neurological decline in the LP patients compared to 3.8% in the fusion patients, and this difference was not statistically significant.

This paper adds to the literature pointing out the negative aspects of LP and led the authors to conclude that LP should be reserved for older, lower demand patients who were at increased risk of complication with fusion. Before making strong conclusions, the limitations of the study must be considered. A meta-analysis is only as good as the studies included, and this analysis included many small case series which provide relatively low grade evidence due to the high risk of confounding. Additionally, the fusion group included heterogeneous surgical techniques, and the outcomes may have varied with different approaches. The definitions of OPLL progression and neurological decline also varied across studies. The analysis comparing rates of neurological decline was underpowered due to the relatively low event rates, and this is evident in that the LP group had over twice the rate of neurological decline as the fusion group, yet this was not statistically significant. Despite these limitations, this paper makes it clear that OPLL progression is much more common after LP than fusion (8-fold more common in this analysis). The more important question that was not answered was whether or not this is clinically meaningful. Given that the rate of neurological decline was twice as high in the LP group, it suggests that progression may have negative consequences in some patients. The authors’ conclusion that LP may be favored in elderly, low demand patients with medical comorbidities seems reasonable, while LF may be better for the younger, healthier patients. An RCT with long-term follow-up would be necessary to determine the answer to this question definitively.

Please read Dr. Lee’s article in the June 15 issue. Does this change your view of laminoplasty for OPLL? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor