The Spine Blog

Friday, April 21, 2017

Large administrative and clinical databases have been widely used in the recent spine literature in efforts to answer clinically important questions. The biggest advantage of these databases is in the sheer volume of patients available for analysis, frequently numbering in the tens to hundreds of thousands. The disadvantages of these datasets as compared to those generated prospectively to answer a research question are many, namely that the large databases can include inaccurate claims data, are frequently limited to very short follow-up, and generally include no patient reported outcomes. The large databases are most useful to analyze large-scale epidemiologic trends (i.e. rates of certain surgeries) and geographic variation. They are almost worthless in evaluating long-term patient outcomes. Their utility in studying complications is debatable, though they do have the advantage of including huge numbers of patients that allows for the study of rare complications. In order to better understand the reliability of large datasets to study complications following ACDF, Dr. Cho and colleagues from New York performed identical analyses using the National Surgical Quality Improvement Program (NSQIP) and National Inpatient Sample (NIS) databases. The NSQIP cohort included over 10,000 patients, while the NIS was a 20% stratified sample that represented over 100,000 cases. There were significant baseline differences between the two cohorts, with the NSQIP including more patients over 65 years old, more blacks, fewer Hispanics, and a generally higher rate of comorbidities (other than renal disease). The overall complication rate was slightly higher (7% vs. 6%) in the NIS, though the rates of specific complications were very low (i.e. 1/10,000 mortality, even lower for wound complications). The authors performed a multivariate regression analysis with both datasets in order to identify independent risk factors for mortality, cardiac complications, and sepsis. In general, each cohort had different risk factors for each complication, with the only examples of consistent risk factors being age for all three complications, male gender for mortality, diabetes for cardiac complications, and bleeding disorder for sepsis. A striking difference was how recent weight loss was a very strong predictor of all three complications (odds ratio of 50 for sepsis) in the NIS, while it was not a significant independent predictor of any complication in NSQIP.

This paper does a nice job demonstrating the advantages and limitations of large database analyses. Complications following ACDF are rare, with mortality occurring at a rate of approximately 1/10,000 according to this study. Such rare events cannot be studied with traditional prospective clinical studies, so the databases allow for a glimpse into these events. However, in this case, events such as death (occurring in 11/10,000 NSQIP patients) and wound complications (3/10,000) were so rare that even this study was underpowered to analyze them well. Given the very low numbers of complications and different definitions of risk factors and complications across the two databases, it is not surprising that the multivariate analyses yielded different results. The authors point out the biggest limitation of the NIS, which is that is includes only data for the duration of a single hospital admissions. Given that the average admission for ACDF is under two days, this database most likely misses the vast majority of complications that occur. The NSQIP is somewhat better and likely captures many more complications that present within 30 days of discharge, but it misses complications such as pseudarthrosis, hardware failure, and adjacent segment degeneration. While these databases can identify medical complications and some infections that occur in the short term following surgery, most of the important events occur well beyond 30 days after spine surgery. The inability of these studies to capture long-term reoperation rates and patient reported outcomes markedly limits their utility beyond describing large scale epidemiologic trends.


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

Adam Pearson, MD, MS

Associate Web Editor

Friday, April 14, 2017

Debate over the best surgical technique for degenerative spondylolisthesis (DS) has been ongoing for over twenty years, with no single technique being universally adopted. While fusion has been considered a mainstay of treatment since Herkowitz and Kurz’s landmark paper in 1991,1 recent RCTs have called into question the need for a fusion.2,3 Assuming a fusion is favored for many patients, the best fusion technique remains unknown. The Spine Patient Outcomes Research Trial showed no differences in patient reported outcome measures among uninstrumented fusion, instrumented fusion, and interbody fusion, though this was not a randomized study.4 Despite the lack of strong evidence supporting interbody fusion for DS, this technique is one of the most frequently used in the United States.5 On this background, Dr. Challier and colleagues from France performed an RCT comparing decompression with posterolateral instrumented fusion (PLF) to decompression, posterolateral instrumented fusion, and transforaminal lumbar interbody fusion (TLIF). They randomized 60 patients with DS and followed them for two years. There were no significant differences in patient reported outcome measures (ODI, SF-36, VAS) for the two fusion groups, though there was a trend towards a greater improvement in ODI at two years for the TLIF group (28 point improvement vs. 19 point improvement, p=0.08). The TLIF group had a significantly higher radiographic fusion rate (93% vs. 43% according to Lenke classification). There were no significant differences in spinopelvic parameters. The reoperation rate was low in both groups (3/30 for PLF vs. 1/30 for TLIF). Based on these findings, the authors concluded that adding TLIF did not provide any clinically meaningful benefit.

The authors should be congratulated for performing a very well-designed RCT in an effort to answer an important clinical question. One of the most striking findings is that the fusion rate for the PLF group was so low. This seems likely related to Lenke’s definition of fusion, which required bridging bone over the transverse processes. Frequently, the most robust fusion in PLF using local bone graft is found across the facet joints rather than across the transverse processes, and facet fusion can only be detected using a CT scan. Multiple prior studies have suggested a much higher fusion rate (>80%) for single level instrumented PLF using local bone graft, though fusion definitions varied across these studies.6-8 The fact that there were no significant differences in patient reported outcomes suggests that the lack of intertransverse fusion in the PLF patients generally did not lead to worse outcomes. Another important limitation was that this study was relatively underpowered. Even though the TLIF group improved 9 points more on the ODI score, the difference was not significant. The MCID on the ODI is likely around 10 points, so this borders on a clinically important difference that was not statistically significant given the low number of patients enrolled. This paper adds to the evidence that exists suggesting that adding a TLIF does not significantly improve clinical outcomes for the average DS patient. However, DS represents a wide spectrum of pathology, ranging from patients with a low grade, stiff, stable slip with a collapsed disk space to those with a higher grade, hypermobile slip with a preserved disk. The ideal surgical technique likely varies depending on patient and radiographic characteristics, but we do not currently have evidence to support the use of different techniques in patients with different pathology. Until we do, surgeons will have to rely on their experience and judgment to perform the operation they believe best fits each patient.

Please read Dr. Challier’s article on this topic in the April 15 issue. Does this change how you view the use of TLIF for DS? Let us know by leaving a comment on The Spine Blog.


Adam Pearson, MD, MS

Associate Web Editor



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.            Forsth P, Olafsson G, Carlsson T, et al. A Randomized, Controlled Trial of Fusion Surgery for Lumbar Spinal Stenosis. N Engl J Med 2016;374:1413-23.

3.            Ghogawala Z, Dziura J, Butler WE, et al. Laminectomy plus Fusion versus Laminectomy Alone for Lumbar Spondylolisthesis. N Engl J Med 2016;374:1424-34.

4.            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.

5.            Kepler CK, Vaccaro AR, Hilibrand AS, et al. National trends in the use of fusion techniques to treat degenerative spondylolisthesis. Spine (Phila Pa 1976) 2014;39:1584-9.

6.            Inage K, Ohtori S, Koshi T, et al. One, two-, and three-level instrumented posterolateral fusion of the lumbar spine with a local bone graft: a prospective study with a 2-year follow-up. Spine 2011;36:1392-6.

7.            Kang J, An H, Hilibrand A, Yoon ST, Kavanagh E, Boden S. Grafton and local bone have comparable outcomes to iliac crest bone in instrumented single-level lumbar fusions. Spine 2012;37:1083-91.

8.            Sengupta DK, Truumees E, Patel CK, et al. Outcome of local bone versus autogenous iliac crest bone graft in the instrumented posterolateral fusion of the lumbar spine. Spine (Phila Pa 1976) 2006;31:985-91.



Friday, April 7, 2017

Unplanned readmission following elective spinal surgery is a large driver of cost and patient dissatisfaction. Policy makers have focused on reducing 30-day readmission rates by instituting financial penalties for institutions with high readmission rates, though the effectiveness of these policies is unclear. If readmission rates can be reduced, the value of spine surgery will be increased substantially as it indicates increased quality with reduced cost. Given the importance of reducing readmission rates, Dr. Adogwa and colleagues from Duke University Hospital reviewed a consecutive series of 1,400 elective spine surgery patients and identified 132 who were readmitted to their hospital within 30 days of discharge (a 9.4% readmission rate). The most common reason for readmission was surgical site infection (35% of readmissions), followed by insufficient pain control (20%). Most of the other readmissions were related to medical conditions. Of the readmitted patients, 93% had undergone a fusion operation, with the majority having undergone either lumbar or thoracolumbar fusion. While there was no comparison to the non-readmitted patients, the readmitted patients appeared to have had a relatively high comorbidity burden, with 42% having diabetes, 36% smoking, and 25% with depression. Additionally, 45% had been initially discharged to a skilled nursing facility or acute inpatient rehab. Among those readmitted, 27% required a return trip to the OR, and the average length of stay for the readmission was 7.6 days.

This study does a nice job confirming what most spine surgeons know through their experience, namely that most readmissions are for surgical site infection or insufficient pain control. The study could have been more powerful if the authors had compared the readmitted group to the non-readmitted group in order to determine risk factors for readmission, some of which may be modifiable. While the readmitted group had a high proportion of smokers and diabetics, it is unclear if the non-readmitted group had lower rates of these comorbidities. Similarly, it seems likely that patients undergoing more invasive surgery had higher readmission rates, though no comparative data was presented to allow one to make this conclusion. The results do make it clear that reducing infection rates and improving post-operative pain control would result in fewer readmissions. Surgical site infection is a challenging problem on which to make more progress as it has been aggressively pursued already at most institutions. The use of vancomycin powder in instrumented cases was a recent advance that has resulted in significantly lower infection rates. Pre-operative protein malnutrition may be another modifiable target that could be addressed to reduce infection rates. Post-operative pain control has received less attention in the literature, and it is an area where many spine surgery programs could likely improve. With the increased scrutiny on the use of narcotic pain medication, this may be an opportunity to increase collaboration between the spine surgery and pain services. I have personally found my colleagues in the pain management group to be extremely helpful, and we are working towards more co-management of patients who struggle with pain control and narcotic use. Hopefully papers such as this one will serve as an impetus to look at ways to reduce infection rates, improve post-operative pain control, and better coordinate post-discharge care. If policy makers continue to increase financial incentives to avoid readmission, institutions that perform spine surgery will undoubtedly focus even more on this in the future.


Please read Dr. Adogwa’s article on this topic in the April 1 issue. Does this affect how you view efforts to reduce readmission following spine surgery? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

Friday, March 31, 2017

Friday, March 24, 2017

There is an established literature demonstrating that high volume surgeons and hospitals have better outcomes, fewer complications, and lower costs than low volume surgical programs. 1,2 However, data on the relationship between surgeon volume and outcomes in cervical spine surgery are scant. As such, Dr. Basques and colleagues from Chicago used the National Inpatient Sample (NIS) from 2003-2009 to evaluate the association between surgeon volume and complications and costs for patients undergoing anterior cervical fusion (ACF). They divided surgeons into low (25th percentile or less, under 6 cases/year), medium (25th-74th percentile, 6-66 cases/year), and high (75th percentile or higher, more than 66 cases/year) volume cohorts. The low volume surgeons’ patients were older, more likely to be on Medicare or Medicaid, had a higher proportion of males, and a higher comorbidity burden compared to the medium and high volume surgeons. Using a statistical model controlling for age, sex, comorbidity burden, and insurance status, they found that low volume surgeons had an over 3-fold higher rate of any inpatient complication, while high volume surgeons had a 30% lower complication rate compared to the medium volume cohort. Length of stay was over 2 days longer in the low volume group and 0.3 days shorter in the high volume group. Inpatient costs were over $4,500 higher in the low volume group and $1,200 less for the high volume group. Based on these data, the authors concluded that the typical surgeon volume-outcomes relationship held true in ACF.

The results of this study come as no surprise given the consistent findings across disciplines that increased surgeon and hospital volumes result in better outcomes with decreased complications and lower costs. While this study provides a very high level view of the topic, the important causative details that underlie this relationship remain obscure with such a study design.  One of the major limitations of the NIS is that only inpatient complications for the index admission are recorded, and these complications are oftentimes not the most relevant for the procedure under consideration. In this study, included complications included death, pneumonia, acute kidney injury, urinary tract infection, MI, sepsis, surgical site infection, and durotomy. Given that the overall complication rate including all of these was only 1.3%, the rate of any individual complication was clearly very low. The inpatient complications more germane to ACF such as neurological injury, re-operation, esophageal injury, vascular injury, and dysphagia were not recorded, and complications seen most frequently after discharge including readmission, hardware failure, surgical site infection, pseudarthrosis, and adjacent segment disease could not be captured with the NIS. Another limitation was the failure to control for hospital volume, which likely played a greater role in affecting the outcomes measured in this study than surgeon volume. Finally, the study did not control for different diagnoses, so non-elective cases performed for trauma, infection, or tumor were lumped together with the more common degenerative cases. This study makes a reasonably good case that higher volume surgeons have fewer complications and are more efficient in resource utilization than lower volume surgeons performing ACF. However, we still do not know exactly why this relationship holds true or how to transfer some of the effective practices of high volume surgeons to their low and medium volume counterparts.

Please read Dr. Basques’s article on this topic in the March 15 issue. Do you believe the relationship between surgeon volume and outcomes holds true in your institution? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor



1.            Davies JM, Ozpinar A, Lawton MT. Volume-outcome relationships in neurosurgery. Neurosurg Clin N Am 2015;26:207-18, viii.

2.            Lau RL, Perruccio AV, Gandhi R, Mahomed NN. The role of surgeon volume on patient outcome in total knee arthroplasty: a systematic review of the literature. BMC Musculoskelet Disord 2012;13:250.