The Spine Blog

Friday, June 16, 2017

Conservative treatment of pediatric lumbar spondylolysis with rest and bracing has been shown to be effective for those with acute symptoms. Traditionally, diagnosis was based on radiographs and CT scan, with chronicity and healing potential evaluated by bone scan. More recently, MRI has been used to define the chronicity of spondylolysis, with edema detected on fluid sensitive sequences indicative of acute spondylolysis with healing potential. The duration of treatment needed to achieve healing has not been well-defined using both clinical and radiographic parameters. As such, Dr. Sakai and colleagues from Japan studied 60 children (average age 13 years) with lumbar spondylolysis based on clinical findings, CT scan, and MRI. Among these 60 children, 65 lamina were involved, 21 of which had bilateral spondylolysis. They classified the lysis as very early (high signal change on MRI, no fracture on CT) in 27, early (high signal change on MRI, non-displaced fracture) in 16, progressive (high signal change on MRI, displaced fracture on CT) in 15, and terminal (no increased signal on MRI, displaced fracture on CT) in 19. Patients were treated with rest, abstinence from sports, and a rigid brace. They were evaluated monthly with physical exam and repeat MRI until they were pain free and MRI showed no high signal change. At this point, they underwent CT scan to evaluate for bony healing. The healing rate was 100% for very early patients (average healing time 2.5 months), 94% for early patients (2.6 months), 80% for progressive (3.6 months), and 0% for terminal. While the healing rates were high for the non-terminal patients, the recurrence rate—defined by the return of back pain and high signal change on MRI—was 26% overall. None of the recurrences had a fracture, and all recurrences healed successfully. Two patients in the terminal group underwent surgery for pars repair.

This is a nice study that is most impressive for carefully documenting the healing process in these patients with monthly MRIs and post-healing CT scans to document bony union. Unlike most historical studies, this study included a large group of “very early” patients with stress reactions rather than fractures, all of which “healed”. Including these patients resulted in a higher healing rate than has been observed in some earlier studies, though it is important to have this information for the “very early” group as they are being detected more frequently now that MRI is routine. This paper also does not include patients with spondylolisthesis, so it does not add any information about the healing potential for patients in whom a slip has already developed. This study suggests that the healing potential for early stage spondylolysis and stress reactions is very good, but that there is a relatively high recurrence rate. The timing of recurrence was not well documented, so it is unclear if these cases represented incompletely treated patients—despite radiographic and clinical evidence of healing—or truly new episodes. The outcomes of those who failed to heal are not well-described, so it is unknown if patients who failed to heal radiographically generally had persistent symptoms or not. Given that only 2 patients with terminal spondylolysis underwent surgery, it seems that many patients who fail to heal can remain relatively asymptomatic.

Please read Dr. Sakai’s article on this topic in the June 15 issue. Does this change your view on the healing potential of pediatric lumbar spondylolysis? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor

 


Friday, June 9, 2017

Over the past 30 years, the overall quality of the spine literature has improved markedly. Most studies now compare outcomes between groups rather than present simple case series, outcomes are now patient reported rather than physician determined, and statistical methods have become much more sophisticated. Additionally, the spine research community has come to understand the need to have sufficiently powered studies and now appreciates the importance of sample size calculations. While spine researchers now pay more attention to statistical power more than their forebears, increasing statistical power requires enrolling more patients, and this demands more time and money, resources that are becoming scarcer. Dr. Froud and colleagues wanted to assess if trials studying low back pain have had increasing power over time. To evaluate this, they identified 383 RCTs evaluating nonspecific low back pain from 1980-2012. They reviewed the trials and determined the sample size, the effect size detectable with the number of enrolled patients, and whether or not an a priori sample size calculation was performed. Effect size was used in order to standardize the analyses across many different outcome measures and is defined as the difference between the groups divided by the standard deviation. The authors suggested that effect sizes above approximately 0.3 typically represented clinically meaningful differences. Among the 383 studies, the average total sample size was 153, and the average number of patients enrolled increased by approximately 1.5 patients per year. While enrollment numbers increased steadily through 2005, beyond that point average enrollment started to shrink. Only 1/3 of trials were powered to detect an effect size of 0.5, and only 5% could detect an effect size of 0.3. Forty-one percent of articles reported an a priori sample size calculation, and that number also tended to rise until 2005 and then decline in later years.

This study makes it clear that low back pain trials have generally been underpowered. Given the resources required to run sufficiently powered studies, it is not surprising that most have been underpowered.  Trials including hundreds of patients typically require multiple sites and millions of dollars, not to mention a highly motivated and dedicated research team. The Spine Patient Outcomes Research Trial (SPORT) was the largest spine-related trial ever performed, and it required 13 different sites and over $20 million to complete. As public and private funding for spine research declines, future efforts of this magnitude are probably not possible without a marked improvement in the efficiency of running clinical trials. As electronic medical records become universal and patients gain the ability to communicate with researchers via their smart phones, it is possible that generating research-quality data is going to get less expensive. The spine research community had better hope so, as increasing funds to perform research do not appear to be on the horizon.

Please read Dr. Froud's article on this topic in the June 1 issue. Does this change how you view the issue of underpowered studies in spine research? Let us know by leaving a comment on The Spine Blog.


Adam Pearson, MD, MS

Associate Web Editor


Friday, June 2, 2017

Anterior cervical discectomy and fusion (ACDF) and cervical total disk replacement (CTDR) are commonly done in an outpatient setting. This practice saves a significant amount of money by moving the procedure from the high cost hospital environment to a low cost outpatient surgery center and also avoids the costs associated with an inpatient stay. There is extensive literature suggesting it is a safe practice. The major risk of outpatient ACDF is the development of a hematoma that compromises the airway or causes spinal cord compression after discharge home. Such an airway complication is a potentially life-threatening event that requires urgent surgical intervention, which can obviously be performed faster if the patient is already admitted to the hospital. Fortunately, such events are rare (under 1%). Other potential problems following ACDF such as insufficient pain control, dysphagia, medical complications, and lack of social support can also be challenging to deal with in the outpatient setting. In an effort to assist spine surgeons with performing outpatient ACDF and CTDR safely, Ms. Mohandas and colleagues convened a modified Delphi panel in order to craft best practice guidelines for outpatient ACDF and CTDR. The panel included 6 spine surgeons, 3 anesthesiologists, and 1 nurse, all of whom had extensive experience with outpatient ACDF. Over 90 best practice statements were developed and then evaluated by the panel, with consensus agreement defined as 70%. The guidelines addressed patient selection, pre-operative care, intra-operative care, first and second stage recovery, home care and follow-up, and practice economics. Consensus was obtained for about 90% of the statements. Notably, the panel did not agree that age over 65, morbid obesity, 3 or more level surgery, myelopathy, and obstructive sleep apnea were contra-indications to outpatient ACDF. They also failed to reach consensus around use of drains and hemostatic matrices. There was widespread agreement on many best practices that could be considered relevant for any outpatient procedure.

The literature has made it clear that outpatient ACDF can be a safe procedure associated with significant cost savings if performed in properly selected patients. This paper had the potential to help with patient selection, however, the panel was not very willing to suggest that many patient characteristics were contraindications to outpatient ACDF. They did agree that active ischemia, significant heart failure, recent MI, and ASA 4 were contra-indications to outpatient ACDF, but these are likely contraindications to any elective surgery, even in the inpatient setting. The authors also endorsed statements indicating that lack of caregiver support or high levels of opioid use pre-operatively were also contraindications to outpatient ACDF. However, beyond that, they do not offer much guidance in patient selection and did not suggest that 3 or more level surgery or morbid obesity should be considered contraindications. Post-operative hematoma, the complication that causes the most trepidation about outpatient surgery, is very rare, difficult to predict, and can occur up to 72 hours post-operatively. As such, the only way to reliably prevent it from occurring after discharge would be to hospitalize all ACDF patients for 72 hours, which is not a reasonable approach. The other problems related to outpatient surgery tend to be pain control, dysphagia, and lack of social support. The guidelines do suggest that surgeons evaluate pain control and social support problems as part of the pre-operative assessment, which should mitigate these issues to some degree. While best practice guidelines can be helpful, their creation through a Delphi process using expert opinion is prone to bias. All of the panelists were likely proponents of outpatient ACDF, and that comes through in their suggestion that it is appropriate for almost any patient and any procedure. Outpatient ACDF is a good, high value procedure when done in the appropriate patient. While these guidelines generally support the practice, I’m not sure they provide surgeons with much specific guidance.


Please read the paper by Ms. Mohandas in the June 1 issue. Does this help you with patient selection or planning for outpatient ACDF? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


Friday, May 26, 2017

There are relatively few prevalence studies looking at lumbar spondylolisthesis, and none have combined radiographs, MRI, and a clinical evaluation. Dr. Ishimoto and his colleagues from Japan involved in the Wakayama Spine Study sought to fill this void by performing a population-based cross-sectional study that evaluated 938 participants over the age of 40. All subjects underwent standing x-rays, lumbar MRI, and a clinical evaluation to determine the presence of back pain, leg pain, and neurogenic claudication. About two thirds of the patients were female, and the average age was 67. Spondylolisthesis was defined as antero- or retrolisthesis greater than 5% of the length of the superior endplate of the caudal vertebra in the motion segment, and both degenerative (DS) and isthmic spondylolisthesis (IS) were included. Thirteen percent of males and 17% of females had spondylolisthesis, and this difference was not statistically significant. Low back pain was about 20% more prevalent in the spondylolisthesis subjects (47% vs. 38%), though this difference did not reach significance either. Symptomatic spinal stenosis, defined as the presence of at least moderate stenosis on MRI and radiculopathy or claudication symptoms, was more than twice as prevalent in patients with listhesis (16% vs. 7%), and nearly three times as common in men with listhesis (20% vs. 8%). The average slip was measured at 14%, and the degree of slip was not related to the presence of symptomatic stenosis.

This paper is a nice cross-sectional study of lumbar spondylolisthesis and represents the first time where a population-based study evaluating lumbar spondylolisthesis included radiographs, MRI, and clinical evaluation. Their findings of nearly equal prevalence among men and women was surprising given that previous studies have found symptomatic DS to be nearly twice as common among women.1 This study did include a mixture of IS, DS, and retrolisthesis (primarily at L3-L4) subjects, so it is possible that the sex-based prevalence differences in DS observed previously were obscured by the inclusion of IS and retrolisthesis patients. Another possibility is that the sex-based prevalence differences in DS are less pronounced in the Japanese population. The major weakness of this paper was the failure to stratify most of the analyses by type of listhesis (i.e. IS, DS, retrolisthesis) as patient characteristics and presenting symptoms can be different among those three subgroups. The association between spondylolisthesis and symptomatic stenosis is not surprising as listhesis of any kind tends to develop with stenosis (i.e. DS tends to cause central and lateral recess stenosis, IS tends to cause foraminal stenosis, and retrolisthesis can cause stenosis in all compartments). The lack of a strong association with low back pain is also not that surprising as listhesis itself does not necessarily cause back pain, but the degenerative changes that accompany it do. As such, the prevalence of back pain is probably similar or only slightly higher in a spondylolisthesis cohort as compared to an age-matched cohort without listhesis (assuming a similar degree of degenerative changes). This finding is in-line with a previous study that showed a similar degree of back and leg pain across spinal stenosis patients stratified by the presence of DS.2 The cross-sectional design of this study limits us to a snapshot in time, so how the radiographic and clinical findings change over time remains unknown. The authors promise a follow-up report in 3 years, which should be illuminating.

Please read Dr. Ishimoto's paper in the June 1 issue. Does this change how you view the association between spondylolisthesis and clinical symptoms? Let us know by leaving a comment on The Spine Blog.

 

Adam Pearson, MD, MS

Associate Web Editor

 

REFERENCES

1.            Weinstein JN, Lurie JD, Tosteson TD, et al. Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis. The New England journal of medicine 2007;356:2257-70.

2.            Pearson A, Blood E, Lurie J, et al. Degenerative spondylolisthesis versus spinal stenosis: does a slip matter? Comparison of baseline characteristics and outcomes (SPORT). Spine (Phila Pa 1976) 2010;35:298-305.

 

 


Friday, May 19, 2017

All spine surgeons are familiar with the time-consuming, frustrating, and stressful experience of trying to determine the appropriate vertebral level in thoracic spine surgery when there are no good radiographic landmarks on which to rely. Unlike cervical and lumbar surgery when the proximity of the occiput or sacrum allows for easy level confirmation, the thoracic spine does not have reliable radiographic landmarks. Counting ribs on the AP fluoroscopic view can help with level confirmation, though significant anatomic variation in the appearance and location of the T12 rib makes this somewhat unreliable. The situation is even worse in the upper thoracic spine, where the shoulder girdle limits visualization. Obesity and osteoporosis complicate the process further as bony structures are more difficult to visualize fluoroscopically. Universal protocols to prevent wrong-site surgery such as marking the site and the “time-out” provide little to no benefit in preventing wrong-level thoracic surgery. Given these challenges, Dr. Madaellil and colleagues from Washington University in St. Louis wrote a succinct technical report describing pre-operative placement of intra-osseous fiducial markers in order to facilitate level identification in thoracic spine surgery. They reported on 19 patients undergoing thoracic spine surgery who had CT-guided placement of a fiducial marker (usually an embolization coil) by interventional radiology prior to surgery. The radiologists placed the marker using a bone biopsy needle advanced into the thoracic vertebra using a transpedicular approach. This allowed for rapid identification of the level intra-operatively using the fluoroscope. They reported no complications related to marker placement and an average cost of under $400.

 

It is rare that a technical report provides interesting fodder for a blog post, but this article is a nice example of a simple technique that can markedly decrease intra-operative radiation exposure, time spent in the operating room localizing the level, surgeon stress, and, most importantly, wrong level surgery. We use this technique at our institution, and it has markedly improved the experience of level identification in the thoracic spine. We used to spend significant amounts of time and radiation to try and find our level using the fluoroscope, and frequently there was at least some degree of uncertainty associated with the process. Now we take one fluoroscopy shot and immediately know where we are. The most challenging aspect related to this technique is probably communicating successfully with the interventional radiologist and having a process that allow for fiducial placement on short notice and during off-hours. Much thoracic spine surgery is non-elective, so having an interventional radiology group that can place the markers on short notice is key to this working well. Additionally, the radiologist needs to target the appropriate level for marker placement, and this generally requires a sagittal MRI view that shows the entire spine so that any anomalous anatomy can be taken into account. While this may not be a groundbreaking new technique, it is a relatively simple solution to a problem that can make thoracic spine surgery vexing. It would be interesting to quantify how much intra-operative time and radiation this method saves, though it is one of those interventions that has obvious benefits and probably does not require an RCT to demonstrate that.

Please read Dr. Madaelil’s article in the May 15 issue. Is this a technique you currently use or would consider adopting? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor