Friday, January 13, 2017
Fortunately for society, gunshot wounds (GSWs) involving the spine and spinal cord are relatively rare. Unfortunately for spine surgeons and researchers, this makes it a particularly difficult topic to study. Unlike blunt force trauma that tends to cause spinal fractures with discoligamentous disruption and instability, penetrating GSWs do not typically cause instability as the soft-tissue stabilizers tend to remain intact. The major clinical problem resulting from GSWs involving the spine is spinal cord or nerve root injury, and these injuries tend to occur at the time of the shooting rather than in a delayed fashion. Given this background, the literature has suggested the surgical treatment of low velocity, civilian GSWs involving the spine is generally unindicated. Given the low number of GSWs involving the spine, there are only a few series in the literature involving large number of patients. In order to fill this void, Dr. Nwosu and colleagues reviewed 489 patients with civilian GSWs resulting in spinal cord or cauda equina injury who presented to Rancho Los Amigos National Rehabilitation Center following acute treatment elsewhere. Of these 489 patients, 91 initially underwent spine surgery. The authors classified the surgery as indicated or not-indicated according to literature-based standards, with indicated surgery including removal of bullets from the lumbosacral spinal canal, removal of subcutaneous symptomatic bullets, and persistent CSF leak beyond 5 days. Surgery for removing a bullet from the cervical canal for root escape, for decompression of neural elements from non-bullet lesions (i.e. retropulsed bone, hematoma), and for progressive neurological deficit was classified as indicated to give the benefit of the doubt to the decision to operate for these debated indications. Of the 91 index surgeries, 69 (75%) were classified as unindicated. Of these unindicated surgeries, 45% of bullet removals, 95% of decompression/fusions, and 66% of CSF leak repairs were deemed unindicated. Telephone follow-up was performed in a subset of patients, and this revealed a trend towards less neurological improvement and greater pain in the patients treated surgically.
This paper represents the largest series of civilian GSWs involving the spine that has ever been assembled, and the authors should be congratulated on their efforts. The high rate of unindicated surgery revealed by this study reflects the poor understanding of these injuries by the spine surgery community. Given that most spine surgeons do not encounter GSWs frequently, they may apply treatment principles for blunt trauma, with which they are more familiar. As this and other studies have shown, instability due to GSWs is incredibly rare, and even fractures involving all three columns are generally stable. Additionally, the spinal cord injury is generally caused at the time of the shooting, and decompression rarely results in neurological improvement. While this study represents the best study on this topic to date, the limitations inherent in a retrospective cohort study need to be considered. Treatment was not randomized, so the patients taken to surgery were likely substantially different from those treated non-operatively. As such, selection bias may have affected the results. Additionally, only a small proportion of patients provided long-term telephone follow-up, so attrition bias could have affected these data. Nonetheless, this and other studies have suggested that surgical treatment for most civilian GSWs involving the spine is rarely indicated. Hopefully this message will get out to the spine surgery community so that unnecessary surgery and the associated costs and complications can be avoided in this unfortunate group of patients.
Please read Dr. Nwosu's article on this topic in the January 15 issue. Does this change your view on the role of surgery for civilian GSWs to the spine? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor
Saturday, January 7, 2017
The use of intraoperative neuromonitoring (ION) is considered standard of care for deformity correction surgery, but it is also widely used for non-deformity surgery for degenerative conditions in the cervical and lumbar spine. There is scant evidence suggesting that it reduces the rate of intraoperative neurological injury for these cases. In order to better understand trends in the use of ION for ACDF, Dr. Ajiboye and colleagues from Los Angeles used the PearlDiver administrative billing database from 2007-2014 to identify 15,395 patients who underwent ACDF for cervical radiculopathy and/or myelopathy. Patients undergoing anterior-posterior surgery and those being treated for infectious, neoplastic or traumatic conditions were excluded. Overall, 17.1% of these patients had ION performed during their ACDF, with about half being monitored with SSEPs alone and the other half with SSEPs plus MEPs. The rate of perioperative neurological injury was 0.23% for the ION group and 0.27% for the no-ION group. The proportion of monitored patients varied from 22.8% in 2007 to a peak of 32.6% in 2011 and decreased to 4.3% in 2014. Patients under 65 were more likely to be monitored than those over age 65. The use of ION was highest in the West (22%) and lowest in the Midwest (12.9%). Based on these data, the authors concluded that the use of ION did not reduce the rate of intraoperative neurological injury for ACDF.
Given the very low rate of intraoperative neurological injury for ACDF, it is difficult to study the efficacy of ION with sufficient power. As such, a database study may be the only study design that can reasonably address it. Unfortunately, conclusions based on administrative billing data are limited by the type of data captured and the reliability of the coding. In this case, all post-operative neurological deficits within 30 days of surgery were included, so neurological injuries caused by post-operative events such as epidural hematoma would be included along with intraoperative events. Given that post-operative events would theoretically occur with equal frequency in both the ION and no-ION groups, this is unlikely to bias the comparative results, but it could affect the absolute rate of neurological injury. Additionally, surgeons and coders may underreport and fail to code perioperative neurological injuries due to medicolegal concerns. The type of neurological injury is also not documented in the database, so patients who became quadriplegic with complete spinal cord injury were included along with patients with a mild, self-limited C5 palsy. Despite these limitations, this study does suggest that ION does not significantly reduce the rate of intraoperative neurological injury. Given the very low rate of this adverse event, it would be hard to demonstrate the effect of any intervention to reduce it. Intraoperative monitoring is also not a completely benign intervention, given that it commonly yields false-positive results that can lead to aborting a case unnecessarily. It is also expensive and time consuming. Given the potential downside of ION and the lack of evidence supporting its use in routine ACDF, the only indication to use it may be medicolegal. The surgical community seems to be coming to this conclusion, given that ION was used in under 5% of ACDFs in 2014. It remains unclear if it offers an advantage in myelopathy cases where the rate of neurological injury may be higher, and this study did not stratify the results based on diagnosis.
Please read the article by Dr. Ajiboye and colleagues in the January 1 issue. Does this change how you consider the use of ION for ACDF? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor
Friday, December 30, 2016
As we wind down 2016, it is a good time to reflect on what emerged in the spine literature over the past year. One area of intense focus was the role of fusion for degenerative spondylolisthesis (DS), with two RCTs comparing laminectomy alone to laminectomy plus fusion essentially reaching opposite conclusions. The American study demonstrated a lower reoperation rate and somewhat better patient reported outcomes for those who underwent fusion in addition to laminectomy, while the Swedish study demonstrated no advantage for fusion. 1,2 Spine readers responded to a quick poll on the topic after the publication of these papers, and a plurality (47%) noted that laminectomy and instrumented fusion was their preferred operation for single level DS without frank instability. Twenty-six percent favored laminectomy alone, 21% preferred laminectomy and interbody fusion, and 5% laminectomy and uninstrumented fusion. A recent meta-analysis on the topic noted no advantage to adding an interbody fusion when compared to laminectomy and fusion for DS.3 Another approach to DS that has gained popularity over the past decade is the MIS-TLIF, though there is not much literature major advantages to the technique. A prospective cohort study comparing MIS to open TLIF by Guan et al. published in Spine earlier this year reported lower blood loss in the MIS-TLIF group but similar patient reported outcomes.4 Contrary to conventional wisdom, the MIS-TLIF group had a longer length of stay than the conventional open procedure. Opinions on this topic were mixed among the Spine readership, with 58% of quick poll respondents feeling that MIS-TLIF offered advantages over open TLIF, while 42% did not.
The cost and value of spine surgery was also a hot topic in 2016. In one study, Kazberouk et al. showed 30-40% variation in costs for a variety of common spine procedures, with the greatest variation (80%) observed for lumbar fusion.5 When asked about the best way to reduce spine surgery costs, readers answered sticking to indications (71%), avoiding complications (14%), and decreasing length of stay (14%). Interestingly, no readers answered minimizing implant costs, while Kazberouk et al. reported that different implant choices was the main driver in cost variation. The use of BMP-2 remained a controversial topic due to its high cost and possible adverse effects. In a meta-analysis by Laurie et al., the authors analyzed subgroups that may have benefited from BMP-2 and reported that smokers had a significantly higher fusion rate when BMP-2 was used, though this was not reflected in better patient reported outcomes.6 When spine readers were queried about BMP-2 use, 40% of readers reported using it for pseudarthrosis, 20% for long fusions to the pelvis, 7% in smokers, and 33% for all of those indications. The association between BMP-2 and cancer continues to be debated. An August 2016 Spine article by Dettori et al. evaluated the link between BMP-2 use and cancer in a Washington state database and reported no connection.7 Despite most evidence showing no link between BMP-2 and cancer, 60% of quick poll respondents believed BMP-2 does cause cancer. One of the most controversial hypotheses in the spine world recently has been the concept that disk degeneration is caused by bacteria.8 A recent study by Coscia et al. showed a high rate of positive cultures of disk material removed for a variety of indications, with patients being treated for degenerative conditions having a significantly higher rate of positive cultures compared to trauma patients.9 Quick poll respondents were divided on the topic, with 50% believing bacteria play a role in disk degeneration, while the other half believed there was no link.
What do you believe will be the important topics in Spine in 2017? Let us know by leaving a comment on The Spine Blog. Happy New Year!
Adam Pearson, MD, MS
Associate Web Editor
1. 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.
2. 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.
3. McAnany SJ, Baird EO, Qureshi SA, Hecht AC, Heller JG, Anderson PA. Posterolateral Fusion Versus Interbody Fusion for Degenerative Spondylolisthesis: A Systematic Review and Meta-Analysis. Spine (Phila Pa 1976) 2016;41:E1408-E14.
4. Guan J, Bisson EF, Dailey AT, Hood RS, Schmidt MH. Comparison of Clinical Outcomes in the National Neurosurgery Quality and Outcomes Database for Open Versus Minimally Invasive Transforaminal Lumbar Interbody Fusion. Spine (Phila Pa 1976) 2016;41:E416-21.
5. Kazberouk A, Sagy I, Novack V, McGuire K. Understanding the Extent and Drivers of Interphysician Cost Variation for Spine Procedures. Spine (Phila Pa 1976) 2016;41:1111-7.
6. Laurie AL, Chen Y, Chou R, Fu R. Meta-analysis of the Impact of Patient Characteristics on Estimates of Effectiveness and Harms of Recombinant Human Bone Morphogenetic Protein-2 in Lumbar Spinal Fusion. Spine (Phila Pa 1976) 2016;41:E1115-23.
7. Dettori JR, Chapman JR, DeVine JG, McGuire RA, Norvell DC, Weiss NS. The Risk of Cancer With the Use of Recombinant Human Bone Morphogenetic Protein in Spine Fusion. Spine (Phila Pa 1976) 2016;41:1317-24.
8. Albert HB, Sorensen JS, Christensen BS, Manniche C. Antibiotic treatment in patients with chronic low back pain and vertebral bone edema (Modic type 1 changes): a double-blind randomized clinical controlled trial of efficacy. Eur Spine J 2013;22:697-707.
9. Coscia MF, Denys GA, Wack MF. Propionibacterium acnes, Coagulase-Negative Staphylococcus, and the "Biofilm-like" Intervertebral Disc. Spine (Phila Pa 1976) 2016;41:1860-5.
Friday, December 23, 2016
Propionbacyterium acnes (P. acnes) and coagulase-negative staphylococcus (CNS) have been known to be present in the human intervertebral disk for many years. However, whether these bacteria represent an active infection causing disk degeneration, harmless endemic micro-organisms, or contaminants remains unknown. Interest in this topic spiked following publication of a Level 1 RCT that demonstrated significant improvements in low back pain and disability in chronic low back pain patients with Modic type 1 changes following antibiotic treatment compared to a group receiving placebo.1 The current study aimed to add more evidence on this topic by gathering disk material from 169 disks at the time of surgery and then performing extended duration culture and pathologic analysis on the specimens. The patients underwent surgery for a variety of pathology including cervical disk herniation, lumbar disk herniation, lumbar degenerative disk disease, thoracolumbar deformity, and trauma. Overall, 45% of disks had positive cultures, with P. acnes and CNS being the most commonly isolated organisms. Disk material from patients being treated for cervical (63%) or lumbar (65%) disk herniation was the most likely to grow positive cultures, while disks from deformity (30%) and trauma (27%) patients were the least likely to have positive cultures. The authors did not specifically compare other patient characteristics between culture positive and negative patients, though they reported no significant differences between these two group. However, there were reportedly trends towards differences in gender (p=0.07) and age (p=0.1) between the culture positive and negative groups. The pathologic analysis demonstrated no signs of active infection or inflammation, leading the authors to conclude that the bacteria existed in a biofilm without generating a significant immune response. There was no correlation between imaging findings and positive cultures.
The role of low virulence bacteria in disk degeneration remains poorly understood. The strongest evidence to suggest that the presence of bacteria in the disk is a pathological condition leading to disk degeneration and pain is the study by Albert et al. demonstrating a positive response to antibiotics. This study has not been replicated, so the role of antibiotics in the treatment of chronic low back pain remains hotly debated. Given the high rate of positive cultures in the "non-degenerative" conditions (i.e. deformity and trauma) and the substantial number of patients with degenerative disks with negative cultures, the relationship between bacterial colonization and disk degeneration is not a simple one. This study would have been better if the authors had included a table of patient characteristics stratified by culture status to determine if there were differences in the groups beyond the presence of disk degeneration. For example, was there a possible relationship between culture status and age, gender or other comorbidities that the study was underpowered to detect? The current study adds some important data demonstrating that bacteria can be present in disks across a broad spectrum of spine pathology, but that colonization is more common in degenerative disks. Proving that these low virulence organisms cause disk degeneration is difficult with observational designs, but further studies evaluating the response to antibiotics would be very helpful in answering this question.
Please read Dr. Coscia's article on this topic in the December 15 issue. Does this change how you view the role of bacteria in disk degeneration? Let us know by leaving a comment on The Spine Blog. Happy Holidays!
Adam Pearson, MD, MS
Associate Web Editor
1. Albert HB, Sorensen JS, Christensen BS, Manniche C. Antibiotic treatment in patients with chronic low back pain and vertebral bone edema (Modic type 1 changes): a double-blind randomized clinical controlled trial of efficacy. Eur Spine J 2013;22:697-707.
Friday, December 16, 2016
Astronauts on long missions in microgravity are known to be at risk for muscle atrophy and also develop low back pain at a rate higher than on Earth. Efforts have been made to create in-flight strength and conditioning programs, though those have tended to focus on large muscles in the extremities rather than on the core muscles. Given the elevated rate of low back pain and disk herniation in astronauts after spaceflight, Dr. Chang and colleagues designed a study to investigate anatomic changes in the astronaut spine. They performed supine lumbar MRI pre-flight, immediately post-flight (within 2 days of landing), and then at approximately 6 weeks post-landing in 6 astronauts who spent an average of 6 months at the international space station. They found that the functional cross sectional area (FCSA, the area of the lean muscle mass) of the paraspinal muscles at L3-L4 decreased by 19% from the pre- to post-flight images, and 68% of the loss was regained prior to the post-recovery MRI. The proportion of total cross-sectional area (TCSA) comprised of lean muscle also decreased, from 86% pre-flight to 71% post-flight, with the post-recovery MRI showing an improvement back to 81%. The TCSA also decreased and then increased with a similar pattern, though these changes were less pronounced and not statistically significant. There were no significant changes in disk height at any point.
This study represents a high quality case series that demonstrates a significant loss of FCSA during spaceflight that partially recovers during the 6 weeks following return to gravity. It suggests that targeting the core muscles during the in-flight conditioning program might be beneficial. While atrophy of the paraspinal muscles during a long exposure to microgravity is not surprising, the relationship between muscle atrophy and pain remains somewhat obscure. The authors did not look at astronaut reported outcomes in this study to determine the extent of back-related pain and disability, so it was not possible to look for correlations between muscle atrophy and symptoms. Similarly, formal strength testing was not performed, so the effect of muscle atrophy on function is unknown. The authors also raised the possibility that back pain in microgravity could be due to postural changes in the spine (i.e. loss of the normal spinal curvature), but this was not investigated and would require upright imaging. I am not sure about the imaging capabilities on the space station, but obtaining upright radiographs in microgravity would provide important information to study this. Future studies should look at the effect of an in-flight core strengthening program on paraspinal muscle size and function. If long space flights to other planets become a reality, the issues surrounding the spine in microgravity will need to be addressed.
Please read Dr. Chang's article in the December 15 issue. What are your thoughts about the spine exposed to microgravity? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor