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Saturday, July 26, 2014

Any reader of the spine literature has come across an increasing number of studies based on large administrative databases recently. Due to the popularity of these studies that were much less common in the spine literature in the past, Drs. Yoshihara and Yoneoka published a journal club article discussing the strengths and limitations of this study design. Before considering the pros and cons of this research approach, it is worth considering why so many administrative database studies are being performed. For one, computing and statistical methods continue to improve, and “big data” are being used more frequently in many disciplines, medicine included. These large databases capture huge numbers of patients, orders of magnitude more than can be followed in a traditional prospective, clinical trial. This allows for the analysis of relatively rare events and the study of subgroups that could never be evaluated in clinical trials that would be markedly underpowered for such analyses. Additionally, clinical trials are becoming increasingly more difficult to perform due to regulatory issues, demands for more rigorous study designs, and a lack of grant funding for such research, especially for spine-related topics. Finally, researchers have discovered that these studies are relatively easy to perform once a database has been obtained and an analyst has learned their way around it. While querying the databases is relatively easy, formulating questions that can actually be answered with administrative databases and using appropriate analytic methodology can be quite difficult.


Administrative databases are very useful for studying treatment trends over time, evaluating regional variation, and calculating costs to payers. They also allow for the study of rare events—like death following spine surgery—and can have enough patients to evaluate the risk factors for these uncommon complications. They also allow for comparison of the rates of certain well-defined complications, such as readmission, reoperation, and death, among different treatment techniques. While these are all worthy research pursuits, one can argue that the most important outcome following spine surgery is patient reported quality of life. These outcome measures are not included in administrative databases. This is the major limitation of spine surgery database studies, and it precludes comparing efficacy among different treatments. Another limitation of many commonly used databases in the spine literature is that they include only inpatient (i.e. the National Inpatient Sample) data from a single hospital admission or are limited to a 30 day window following the date of surgery (i.e. the National Surgical Quality Improvement Program). Given that many of the most concerning complications such as infection, readmission, and reoperation frequently occur outside these windows, studies analyzing complication rates with these databases likely underestimate the true rate of complications. Researchers need to recognize these limitations while designing their studies, and they should limit their questions to those that can reasonably be answered with the available data. Additionally, they need to take into account that patients selected for different procedures were likely different in ways not captured in billing data (i.e. symptoms and physical exam findings, radiographic characteristics, work status, etc.), and these unrecorded differences cannot be controlled for statistically. Journal reviewers and editors also need to be more stringent in evaluating these articles and should not accept an article for publication simply because it included 100,000 patients. Like most powerful tools, large administrative databases have the ability to be of great benefit, yet, if misused, can cause more harm than good.

Please read Dr. Yoshihara’s article on this topic in the July 15 issue. Does this article change how you view large administrative database studies? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

Friday, July 18, 2014

Cerebrospinal fluid (CSF) leakage due to inadvertent durotomy during anterior cervical discectomy and fusion (ACDF) has been thought to be a relatively rare complication, with rates in the literature ranging from 0.5-1%. However, ACDF is a high volume procedure at most institutions that perform spine surgery, so this complication will be encountered at least a handful of times each year at most busy spine centers. Given that the entire literature on this topic consists of case reports and one case series of 13 patients, Dr. Syre and his colleagues from the University of Pennsylvania reviewed their cases of CSF leaks during ACDF. Over an 11 year period, three surgeons performed 1,223 ACDFs and noted 13 CSF leaks during the primary operation (1% rate). Patients with ossification of the posterior longitudinal ligament (OPLL) were excluded. All patients underwent indirect repair during the index operation with a combination of a patch (Gelfoam, Duragen, Surgicel or muscle) and a sealant (fibrin glue or Duraseal). Primary repair was successful in 9 of the 13 patients, with 8 having no post-operative symptoms and 1 suffering a headache that resolved after 2 days of being positioned with the head of bed elevated to at least 30 degrees. The remaining 4 patients had signs and symptoms of persistent CSF leak (some in a delayed fashion) and had lumbar drains placed. This intervention was successful in only one of these patients. Two patients were found to have hydrocephalus and had placement of VP shunts, and one patient had placement of an LP shunt. Permanent CSF diversion resulted in the resolution of symptoms in these three patients. Based on their findings and a literature review, the authors proposed a treatment algorithm that begins with indirect repair at the time of discovery followed by 24 hours with elevation of the head of bed. If there are persistent signs or symptoms of CSF leak, a lumbar drain is placed for 3 days, followed by re-operation and further efforts at repair if CSF drainage fails. For patients with persistent leakage despite re-operation and a lumbar drain, the authors recommend consideration of indwelling CSF diversion, especially in cases of hydrocephalus.


This article is an important case series that provides some very practical guidance for a complication that is likely underreported and understudied. Given that most high volume spine centers will have to deal with CSF leaks following ACDF somewhat regularly, it is helpful to have some guidance about how to treat them in a systematic fashion. It is reassuring that the majority of leaks can be repaired with a patch and sealant without any clinical sequelae. More challenging are cases with persistent leakage, and this study suggested that lumbar drainage was not always successful, with only 1 of 4 patients having resolution with a lumbar drain in this series. The use of indwelling CSF diversion for persistent leakage had not been discussed in the literature previously, and this appears to have been a successful salvage for three patients in this series. While this study provides some much needed guidance for CSF leaks in ACDF, it also raises some important questions. What is the best technique of indirect repair, namely what type of patch and sealant is most effective? What is the role of elevation of the head of bed following surgery? Should the bed be raised to 30 degrees, 60 degrees or 90 degrees? If the patient has a persistent headache, should flat bedrest be considered? What are the risk factors for CSF leak other than OPLL and revision surgery? If there is delayed leakage from the wound or drain site, should this be sutured or does closure increase the risk of meningitis? This is a partial list of the unanswered questions that surgeons face when managing CSF leaks after ACDF. Unfortunately, answering these questions would require a large, prospective, multicenter study, and it seems unlikely that such a study will be undertaken. For now, this study and the proposed algorithm provides surgeons with some much-needed guidance about how to deal with this complication.

Please read Dr. Syre’s article on this topic in the July 15 issue. Does it change your approach to managing CSF leaks following ACDF? Let us know by leaving a comment on The Spine Blog.


Adam Pearson, MD, MS

Associate Web Editor


Friday, July 11, 2014

The Affordable Care Act (ACA) includes provisions to study alternatives to the traditional fee for service payment model, including bundled payments in which payers provide a lump sum payment to the hospital and providers for an entire “episode of care”. The goal is to align the incentives of hospitals and providers and incentivize high quality and efficient care. Additionally, risk is shifted away from payers to hospitals and providers as they do not receive any further payments in cases of complications, re-admissions or other high cost events. Prior to adopting such a model, hospitals, providers, and payers need to have an understanding of the costs and variation in costs involved in the current system. To address this, Dr. Ugiliweneza and her colleagues analyzed the MarketScan data base from 2000-2009 to evaluate almost 200,000 episodes of spine surgery that they captured by using the 13 most common diagnosis related groups (DRGs) for spine surgery. The MarketScan data base includes data from patients with commercial insurance, Medicare, and Medicaid. They calculated the average index hospitalization costs and subsequent post-discharge costs for each of the DRGs for 30, 60, and 90 day bundles. The three most common DRGs were for lumbar fusion (36%), non-fusion spinal surgery (i.e. laminectomy, 24%), and cervical fusion (14%). They reported that the average 30 day cost for inpatient non-fusion spinal surgery was approximately $13,000 (standard deviation $7,800) and that for lumbar fusion was approximately $43,000 (standard deviation $26,000). Post-discharge costs amounted to about 5% of total costs, and there was a minimal increase in costs from 30 to 90 days. Hospitals accounted for 76% of costs, while physician costs made up 14% of the total.


This is the first paper to evaluate the costs of episodes of care in spine surgery, and it provides some data that hospitals, providers, and payers could use when designing a bundled payment plan. Spine surgery is among the highest cost interventions, and payers are motivated to find ways to limit their financial risk for these procedures. Bundled payments shift the risk to the hospitals and providers, which, in a properly designed system, will result in higher quality, more efficient care. Hospitals and providers will be financially motivated to avoid complications and readmissions, and this should be an impetus to improve quality. All payment systems have the potential for perverse incentives, and, depending on the details, health systems might be motivated to underdiagnose and undertreat post-operative complications. Another challenge will be creating methods to account for complex cases and patients, which hospitals and providers might be incentivized to avoid unless the bundled payment plans are appropriately risk adjusted to take into account the increased costs of taking care of these patients. Additionally, bundled payments in spine surgery will likely not be able to be based simply on DRGs given the huge variation of procedures covered by a single DRG, reflected in the large standard deviations around the average costs reported in this paper. Bundled payments will likely play a role in the future of spine surgery, and, as always, the devil will be in the details. This paper takes a good first step in establishing some benchmarks for costs associated with an episode of spine surgery. Hopefully once institutions gain real experience with bundled payments they will report on the clinical and financial results.

Please read Dr. Ugiliweneza’s paper on this topic in the July 1 issue. Does this change your view of bundled payments in spine surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

Friday, July 04, 2014

In the United States and most of the world, spine surgery is performed by both orthopaedic (OS) and neurological surgeons (NS). Patients and referring providers may have beliefs about how training background influences spine surgeon practice patterns and outcomes and may select a surgeon based on this factor. Few studies have evaluated how specialty (OS vs. NS) affects outcomes, so most beliefs held by physicians and patients are based on anecdotal evidence. To address this gap in the literature, Dr. Kim and his colleagues from Chicago used the National Surgical Quality Improvement Program database to compare 30 day complication rates between OS and NS patients undergoing single level lumbar fusion. Data from 2006-2011 were included, and about 3,000 patients were identified for analysis. Due to potential selection bias and confounding, propensity score matching was performed to create two matched groups including about 1,250 patients in each group. The unmatched groups were remarkably similar, with the only significant differences being that the NS group included more smokers and ASA class 3 and 4 patients. After matching, these differences were no longer present. In terms of surgical variables, the NS group included slightly more posterior lumbar interbody fusion patients, and the OS group slightly more anterior lumbar interbody fusion patients. The operative time was about 30 minutes longer for the NS group. The overall complication rate was approximately 7%, and there were no significant differences in overall, surgical or medical complications between the OS and NS patients in either the unmatched or matched analyses. Re-operation and mortality were also similar for the two cohorts.


This study supports the concept that complication rates are not influenced by spine surgeon specialty and should help patients and referring providers overcome biases about theoretical differences between orthopaedic and neurological spine surgeons. While previous literature has suggested that orthopaedic surgeons are more likely to perform fusions than neurosurgeons, it seems as though differences in spine surgery practice patterns between the two specialties are diminishing. 1 Unfortunately, the limited amount of data available in the NSQIP precludes any firm conclusions about the increasing similarity of orthopaedic and neurological spine surgeons. Patient reported measures are the gold standard outcomes in spine surgery, and these are not available in NSQIP. Additionally, the complications captured in NSQIP tend not to be surgeon dependent and are more related to patient factors (i.e. infection rate, medical complications, mortality, etc.) Surgeon influenced technical complications such as nerve injury, dural tear, hardware malposition, and pseudarthrosis are not recorded. The overall complication rate of 7% is also quite low and reflects the limited number of complications captured in the database and the short temporal window included. While this paper indicates that overall complication rates are similar for the two specialties, this outcome is probably not the most important one to patients who are selecting a surgeon. Future studies should consider differences in indications for surgery, type of surgery selected, and patient reported outcomes. These are probably more relevant to patients and referring providers and may show more differences between the two specialties. Most spine surgeons would likely agree that surgeon specialty is probably no longer the major driver of differences in practice patterns and outcomes in spine surgery. It seems as though we are moving towards an era in which spine surgeons are just spine surgeons rather than orthopaedists or neurosurgeons, but it may take a while for the rest of the medical world to realize this.


Please read Dr. Kim’s article on this topic in the July 1 issue. Does this article change how you view the effect of spine surgeon specialty on outcomes? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor




1.            Bederman SS, Kreder HJ, Weller I, Finkelstein JA, Ford MH, Yee AJ. The who, what and when of surgery for the degenerative lumbar spine: a population-based study of surgeon factors, surgical procedures, recent trends and reoperation rates. Can J Surg 2009;52:283-90.


Friday, June 27, 2014

Adjacent segment disease (ASD) is a well-known phenomenon following fusion of any region of the spine. It remains poorly understood, and the degree to which it is iatrogenic or simply represents the natural history of spinal degeneration is still unclear. Regardless of the etiology, surgeons continue to search for ways to decrease the rate at which it occurs and to prevent the subsequent degradation of clinical outcomes and re-operations that can accompany ASD. While patient factors (i.e. genetic predisposition to degeneration, age, smoking, obesity, etc.) are typically beyond surgeon control, technical factors such as type of fusion (i.e. uninstrumented, instrumented, interbody) and damage to the facet joint cranial to the fusion can be modified. Dr. He and his colleagues from China performed an RCT comparing two different pedicle screw trajectories in order to determine if a more lateral starting point and steeper pedicle screw trajectory decreased the rate of ASD at the level superior to the fusion. They randomized 210 patients with L4-5 or L5-S1 isthmic spondylolisthesis undergoing posterolateral instrumented fusion to one of two pedicle screw trajectories:  one with a more medial starting point in the vicinity of the mammillary process and a straighter trajectory and the second with a more lateral starting point at the junction of the transverse process and the lateral border of the facet joint and a more medialized trajectory. They followed all patients for at least 9 years to determine the rate at which they developed radiographic ASD and clinical ASD, the latter defined as needing a re-operation to address symptomatic ASD. They also recorded the final Oswestry Disability Index score. The group with the more lateral starting point developed ASD at a significantly lower rate (52% vs. 72%) and had a significantly lower rate of clinical ASD (0% vs 8%). Final Oswestry scores were similar for the two groups, though there was a trend for the lateral starting point group to do somewhat better (final ODI 20 vs. 24, p=0.07).


This relatively simple study provides reasonably strong evidence that a more lateral starting point results in less radiographic ASD, though it still occurs in the majority of patients. Intuitively, this makes sense, as the superior screw is less likely to cause ASD if it is further away from the unfused adjacent facet joint. Prior studies have shown relatively high rates of facet violation by the superior pedicle screw, and a higher rate of ASD in such a case would be expected.1 Even if the facet is not violated, it seems likely that a screw that is closer to the joint surface will result in increased pressure on the cartilage and potentially accelerate degeneration. The current paper did not perform post-operative CT scans on all patients, and they did not evaluate the rate of facet violation, though it is a reasonable assumption that a more lateral starting point would reduce this. While a more lateral starting point seems preferable in terms of reducing ASD, it can be technically more challenging to insert the screw with such a trajectory, particularly in larger patients. The authors did not comment on the rate of misplaced screws or need for screw revision, but it seems that a more lateral starting point could increase the rate of laterally misplaced screws. This paper does offer further support to the idea of trying to protect the facet joint superior to the fusion as much as possible, and a more lateral starting point seems preferred as long as it can be achieved technically. Given the 52% rate of radioagraphic ASD even with the more lateral starting point, it is clear that more work has to be done. It still remains to be seen if pedicle screw instrumentation improves outcomes in most lumbar degenerative conditions.2 Their use clearly improves fusion rate, but we still do not know if the potentially higher rate of ASD mitigates this benefit.

Please read Dr. He’s article on this topic in the June 15 issue. Will this article change how you place lumbar pedicle screws? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor



1.            Shah RR, Mohammed S, Saifuddin A, Taylor BA. Radiologic evaluation of adjacent superior segment facet joint violation following transpedicular instrumentation of the lumbar spine. Spine (Phila Pa 1976) 2003;28:272-5.

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.


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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.