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Saturday, November 22, 2014

The concept that performing an interbody fusion (IF) in addition to posterolateral fusion (PLF) leads to better outcomes in isthmic spondylolisthesis (IS) goes back to a 2006 paper published by Swan et al. that showed a short-term advantage for anterior-posterior fusion using a femoral ring allograft and pedicle screw instrumentation compared to a posterolateral instrumented fusion (PLF) alone.1 This study included patients with “unstable” IS with hypermobility on flexion-extension x-rays or documented slip progression, and decompression was not performed. With the development of posterior interbody techniques, surgeons extrapolated from those results and used the study as an indication to perform posterior interbody fusion (IF) in isthmic spondylolisthesis. Multiple small studies have yielded somewhat conflicting results about the benefit of interbody fusion in IS, with some showing no benefit with the addition of IF to PLF and others suggesting a higher fusion rate and somewhat better clinical outcome.2,3 Given the lack of data supporting the use of posterior IF in treating IS, Dr. Lee and his colleagues from Korea performed an RCT in which 81 patients under age 60 undergoing surgery for single-level IS in an armed forces hospital were randomized to instrumented PLF or instrumented PLF +PLIF. All patients underwent direct decompression, and local bone and demineralized bone matrix was used for bone graft. The fusion rate, as determined by flexion-extension x-rays and CT scans at 1 and 2 years post-operatively, was approximately 90% in each group, with no significant differences. Patient reported outcomes, including the Oswestry Disability Index (ODI) and VAS scores for back and leg pain, were also similar for the two groups. The only significant difference observed between the two groups was that operative time was about 30 minutes longer for the IF group. The only reported complication was a deep infection in one IF patient.


This very well-designed study suggests that the addition of a posterior IF to PLF adds no significant benefit for IS patients under age 60. This supports the findings of other studies that have looked at this question and reported relatively small or no advantage of adding a posterior IF in IS cases. The major limitation of this study is its potentially limited generalizability. All study participants were Koreans under age 60 being treated at an armed forces hospital, and those in the armed forces were likely more physically fit and motivated than the average IS patient. This is evident in their marked improvement with surgery, with 2 year VAS scores for back and leg pain less than 2 and ODI scores less than 10. A comparable European study reported 2 year ODI scores of 25 following fusion for IS.2 While this study suggests that there may not be a marked benefit to IF for the average IS patient, there may be subgroups who benefit from IF. However, we have not yet clearly defined these subgroups, and further studies would be required to determine if such subgroups exist (i.e. intervertebral hypermobility, higher grade listhesis, etc). While the Swan study suggested that patients with “unstable” IS benefit from the addition of an anterior IF, it is possible that these results do not generalize to patients undergoing posterior IF with direct decompression. The large femoral ring allografts or other interbody devices that can be placed anteriorly may do a better job re-establishing disk height and indirectly decompressing the foraminal stenosis compared to the smaller posterior IF devices. It is also possible that if direct decompression is performed, no IF is necessary. The many surgical techniques currently being employed to treat IS indicate that no one technique has been shown best. However, if similar results are obtained with PLF and PLF + posterior IF, there may be no reason to perform the potentially riskier, longer, and more expensive IF procedure. Hopefully future studies will help define which, if any, IS subgroups benefit from the addition of a posterior IF.


Please read Dr. Lee’s article on this topic on the November 15 issue. Does this change how you view the role of posterior IF in IS? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor




1.            Swan J, Hurwitz E, Malek F, et al. Surgical treatment for unstable low-grade isthmic spondylolisthesis in adults: a prospective controlled study of posterior instrumented fusion compared with combined anterior-posterior fusion. Spine J 2006;6:606-14.

2.            Ekman P, Moller H, Tullberg T, Neumann P, Hedlund R. Posterior lumbar interbody fusion versus posterolateral fusion in adult isthmic spondylolisthesis. Spine (Phila Pa 1976) 2007;32:2178-83.

3.            Musluman AM, Yilmaz A, Cansever T, et al. Posterior lumbar interbody fusion versus posterolateral fusion with instrumentation in the treatment of low-grade isthmic spondylolisthesis: midterm clinical outcomes. J Neurosurg Spine 2011;14:488-96.


Saturday, November 15, 2014

New technology is constantly being introduced across all medical disciplines, and, in the typical case, it offers an improvement over existing technology but at an increased cost. Cost-effectiveness analysis (CEA) was developed to determine if the benefit of a new therapy justifies its increased cost. Cervical disc replacement (CDR) seems to be just such an example. It represents a new approach to treating cervical radiculopathy that comes with the advantages of theoretically decreasing adjacent segment degeneration and eliminating pseudarthrosis as a complication. Dr. McAnany and his colleagues from Mount Sinai and Texas Back Institute performed a formal CEA in order to determine the cost-effectiveness of CDR relative to the traditional treatment, ACDF. They obtained utilities (outcomes in CEA) from the Pro-Disc C IDE trials, rates of complications and re-operations from the literature, and costs from a combination of Medicare DRG payments to hospitals and professional fees based on CPT codes. Cost data from the National Inpatient Sample were also used. They reported that the index CDR operation was approximately $6,000 less expensive than the index ACDF (approximately $16K vs. $22K) and $17,000 less over 5 years ($102K vs. $119K). Based on the 5 year SF-6D data from the Pro-Disc C trial, they determined that CDR was associated with a 3% improvement in utility compared to ACDF, though this was not statistically significant. This analysis would indicate that CDR is both less expensive and marginally more effective than ACDF, a situation known as “dominance” in CEA.


This CEA, like all CEAs, is highly dependent on assumptions. In order to determine which assumptions are major drivers of the conclusions, the authors performed sensitivity analyses in which the variables were evaluated over a wide range of possible values. Not surprisingly, differences in costs and utilities had substantial effects on the outcomes. Determining the costs of medical interventions is notoriously difficult, and it is somewhat surprising that the new technology actually cost less than the established care. It is also surprising that the 5-year cost of either CDR or ACDF was reportedly over 5 times the cost of the index surgery, even with reoperation rates of less than 3% per year. The authors do not explain this point. The difference in utility (0.03) was also quite low and not statistically significant. Finally, the complication and re-operation rates were two to three times higher for ACDF compared to CDR in the industry-sponsored IDE trials. These trials were not blinded, and surgeons may have been less willing to re-operate on CDRs. Taking all of this together, the results are not surprising. If you assume that new technology is both cheaper and more effective than the older technology, one does not need to perform a CEA to show that it is cost-effective.  The real question about cervical CDR is its longevity, and we will not likely know that for years to come.


Please read Dr. McAnany’s CEA in the November 1 issue. Does this change how you view the economics around CDR? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

Friday, November 07, 2014

Intraoperative neuromonitoring has become more common during routine spine surgery. While it was initially used for deformity correction surgery, some surgeons feel it allows for early detection of potentially reversible neurological deficits during any spinal procedure. Outside of deformity surgery, there is no strong evidence in the literature supporting its use. Anecdotally, surgeons have known there is wide variation in its utilization, though this has not been quantified. Given these gaps in the literature, Dr. Ratliff and his colleagues from Stanford used the MarketScan database from 2006-2010 to evaluate the use of neuromonitoring for single level degenerative spine cases including ACDF and lumbar discectomy, laminectomy, and fusion. They analyzed the relationship between the use of neuromonitoring and perioperative neurological complications, the cost of the procedure, and geographic variation in its use. Neurological complications were defined using ICD-9 codes and were not necessarily specific for intra-operative neurological injury. They generally found no differences in the rates of neurological complications between the neuromonitoring and no-neuromonitoring groups, with the exception of lumbar laminectomy, in which no perioperative neurological complications were reported in the monitoring group, and a 1% rate was reported in the no-monitoring group. However, only 600 cases of laminectomy with neuromonitoring were in the database, which likely limited their power to detect the true rate of this relatively rare complication. Neuromonitoring generally increased the cost of the procedure by over $3000, corresponding to a nearly 25% increase for laminectomy and discectomy. There was marked geographic variation across states, with rates of monitoring varying from 0-60% for ACDF, 0.5-58% for lumbar fusion, 0-23% for laminectomy, and 0-21% for discectomy.


The indications for neuromonitoring for routine spine surgery are poorly defined, and this is the first paper to demonstrate the huge variation in its use across the country. Given the lack of evidence or practice guidelines supporting its use, such variation is not surprising. It is highly unlikely that patient factors are driving the variation—New Mexico had the highest rate of monitoring (34%) and neighboring Texas one of the lowest (4%), and chances are the spine patients in the two states are not that different. The authors found no significant correlation between the medicolegal environment and neuromonitoring rates, suggesting that it is probably local culture that determines the rate of use. While the authors looked at variation across states, chances are that even greater variation would be found across hospital systems. This study does a nice job demonstrating the variation in utilization of neuromonitoring, though it does not answer the question of when it is indicated. Fortunately, perioperative neurological deficit is a rare event, though that makes it difficult to study without huge patient samples. Claims databases are likely the only source of data on such a scale, but ICD-9 codes are not sufficiently granular to determine the rate of intra-operative neurological injury (i.e. they do not reliably distinguish stroke from intra-operative nerve root or spinal cord injury). A massive, multi-center prospective study could be entertained, but this would likely need to include tens of thousands of patients and would be very expensive and challenging to coordinate. In the absence of high quality evidence, professional organizations generally cannot issue practice guidelines, and, given the reimbursement involved, the topic is somewhat politically charged. While intra-operative neuormonitoring may detect a rare, reversible neurological injury in routine lumbar decompression, it is probably not a cost-effective intervention. In situations where evidence is lacking, surgeons and hospital systems should use common sense and avoid costly interventions with minimal benefit. Unfortunately, history suggests that when there is money to be made, such restraint is rarely employed until payers limit reimbursement for an intervention.


Please read Dr. Ratliff’s article on this topic in the November 1 issue. Does it change your view on intraoperative neuromonitoring? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

Friday, October 31, 2014

Most spine surgeons agree that degenerative spondylolisthesis (DS) and isthmic spondylolisthesis (IS) are best treated with fusion, but there is much less agreement on the best fusion technique. There are vocal supporters of uninstrumented posterolateral fusion, instrumented posterolateral fusion, posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), and anterior-posterior fusion. Studies on this topic have generally included small numbers of patients, with the exception of the SPORT study that performed a post-hoc subgroup analysis comparing outcomes among DS patients treated with uninstrumented posterolateral fusion, instrumented posterolateral fusion, and PLIF.1 SPORT found no differences in patient reported outcomes among the different fusion techniques out to four years, though fusion rate did increase with the use of instrumentation and interbody devices. Given the lack of large studies looking at the topic, Dr. Liu and his colleagues from Beijing elected to perform a meta-analysis comparing patient satisfaction, fusion rates, and complications between instrumented posterolateral fusion (PLF) and PLIF. They included 4 RCTs and 13 observational studies, which represented a mixture of IS and DS. The authors divided the PLIF patients into those who had bone graft placed posterolaterally as well as in the interbody space (PLIF + PLF) compared to those with bone graft only in the interbody space (PLIF). They reported that PLIF patients had significantly greater satisfaction and fusion rates compared to PLF patients, and there was a trend towards lower complication rates in the PLIF group. Results were similar for the PLIF+PLF group compared to the PLIF patients.


Meta-analyses are only as good as the studies that are included, and limitations such as bias and confounding present in the original study cannot be mitigated statistically. Many of the included studies had methodological flaws, and this study did not solve those problems. Additionally, the authors combined DS and IS patients despite the fact that these are two very different pathologic processes that affect two distinct patient populations. What works for DS might not work in IS, and vice versa. The description of how patient satisfaction was measured was quite limited, despite this being the primary outcome measure. Fusion status was also defined differently across the studies, and bone graft material also varied. All these factors contributed to relatively high heterogeneity among the studies, which limits the conclusions that can be drawn. This paper generally supports what has been shown in the literature in the past:  PLIF increases fusion rate but has a minor effect on patient reported outcomes. A somewhat surprising outcome from this analysis was the finding that complication rates were somewhat lower in the PLIF group. Given that PLIF is somewhat more invasive PLF, one would not expect lower complication rates for PLIF other than possibly a lower pseudarthrosis rate. This paper has enough limitations to preclude any strong conclusions, but it does shine a light on an important topic that should be studied further. The question of the best fusion technique for DS and IS could easily be studied in RCTs. However, there are probably patient and disease characteristics that modify the treatment effect of the various fusion techniques, and multiple subgroup analyses would probably be necessary to determine the best fusion technique for each individual patient.

Please read Dr. Liu’s article on this topic in the October 15 issue. Does this change how you consider fusion techniques for lumbar spondylolisthesis? Let us know by leaving a comment on The Spine Blog.


Adam Pearson, MD, MS

Associate Web Editor



1.            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.


Friday, October 24, 2014

As healthcare-resources become more limited, the spine community has focused more on improving the value of care. Value is defined as quality/cost, so either improving quality without increasing cost or maintaining quality while decreasing cost can both increase value. Many efforts towards improving value have involved creating evidence-based pathways to standardize care in a manner that maximizes quality in a cost-effective manner. In the treatment of low back pain (LBP), advanced imaging and surgeon referral are two high cost items, and current guidelines suggest that most LBP patients need neither.1 In the United States, there are no formal controls over advanced imaging or surgeon referral, and both are readily available without long wait times. However, in many single-payer systems such as in Canada, MRI scanners and spine surgeons are in relatively short supply, which creates long wait times for both. While efficient use of expensive resources should be the goal of any health system, the motivation for improved triage of LBP patients to advanced imaging and spine surgery consultation is stronger if access is difficult. In order to improve the rate of appropriate use of advanced imaging and surgeon referral, the Saskatchewan Ministry of Health created the Saskatchewan Spine Pathway that allows PCPs to classify patients as having one of four pain patterns (LBP worsened with flexion, LBP worsened with extension, predominant leg pain that is constant and mechanical, and predominant leg pain with extension) based on the history and a brief physical exam. They then suggest self-care exercises specific for each pain pattern and refer patients to a physical therapist-run spine clinic if they fail to improve quickly. The therapists then re-assess the patients and refer the leg pain predominant patients for MRI and surgical referral if self-care is not helping, while they coordinate non-surgical care of the predominant back pain patients. After instituting this pathway, the authors retrospectively evaluated the rate of appropriate surgical referrals for patients treated on the pathway and those referred via the traditional process. They found that 60% of patients referred via the pathway were surgical candidates compared to 37% referred via the traditional process. The authors noted that historically only 15% of surgeon referrals were surgical candidates, though prior to the start of the study, the PCPs had undergone training in appropriate surgical referrals, which seemed to have improved the process to some degree. Additionally, 75% of the patients referred via the pathway had predominant leg pain compared to 55% referred via the traditional process.


This study suggests that the use of scarce and expensive resources such as MRI scanning and spine surgeon referral can be made more efficient through the use of a non-MD staffed triage clinic, which has likely improved the value of spine care in Saskatchewan. While health services research such as this is outside the realm of traditional basic science or clinical outcomes studies, this type of work is going to become increasingly important as we strive to improve value in healthcare. This analysis was unblinded, non-randomized, and retrospective, so the results should be viewed as preliminary, but the findings support the experience of most spine surgeons. The majority of spine surgeons in the United States have likely developed some form of triage system within their practice to increase the likelihood that the patients they see are candidates for surgery. However, very little has been written about this topic that is very important to providers trying to run an efficient clinic. The challenge in the United States with its decentralized healthcare system is to motivate referring PCPs to engage in such a program. It is much easier for a PCP to simply order an MRI and refer a patient with chronic LBP to a spine surgeon than trying to classify their pain pattern and start a self-care program. While such PCP engagement may not be possible outside of centralized health systems, the establishment of algorithm-driven, non-MD triage clinics could potentially improve the rate of appropriate imaging and surgical referral and substantially decrease costs. Quality may also improve as chronic LBP patients would probably be less likely to be subjected to ineffective pharmacological and interventional treatments, and patients with radiculopathy and claudication could be referred to a surgeon more rapidly. As individual practices consolidate into larger practice organizations in the United States, developing more organized care pathways such as this may become more of a reality. Hopefully further data from Saskatchewan will be emerging including the effect of the pathway on appropriate use of advanced imaging and on the cost of treating these patients.


Please read Ms. Wilgenbusch’s article in the October 15 issue. Does this article change how you view the triage of LBP patients? Let us know by leaving  a comment on The Spine Blog.


Adam Pearson, MD, MS

Associate Web Editor



1.            Chou R, Qaseem A, Snow V, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med 2007;147:478-91.


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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.