The Spine Blog

Friday, June 23, 2017

Laminoplasty (LP) is an attractive treatment option for myelopathy in the setting of ossification of the posterior longitudinal ligament (OPLL). A posterior approach avoids the risk of durotomy associated with anterior procedures, and LP has a lower perioperative complication rate compared to the more invasive laminectomy and fusion (LF). Additionally, adjacent segment degeneration is less common with the non-fusion procedure. Potential downsides of LP include increased neck pain, kyphosis, and OPLL progression. There is little data on the rates of OPLL progression following LP compared to fusion procedures, so Dr. Lee and colleagues from Korea performed a meta-analysis comparing OPLL progression and neurological decline between laminoplasty and fusion procedures (including both anterior and posterior fusions). They identified 11 studies including 530 patients, 6 of which were laminoplasty case series and the other 5 included various combinations of LP and fusion patients. They calculated an OPLL progression rate of 65% in the LP group compared to 8% in the fusion group, a statistically significant difference. They also found that the rate of progression increased with time. The meta-analysis demonstrated an 8.3% rate of neurological decline in the LP patients compared to 3.8% in the fusion patients, and this difference was not statistically significant.

This paper adds to the literature pointing out the negative aspects of LP and led the authors to conclude that LP should be reserved for older, lower demand patients who were at increased risk of complication with fusion. Before making strong conclusions, the limitations of the study must be considered. A meta-analysis is only as good as the studies included, and this analysis included many small case series which provide relatively low grade evidence due to the high risk of confounding. Additionally, the fusion group included heterogeneous surgical techniques, and the outcomes may have varied with different approaches. The definitions of OPLL progression and neurological decline also varied across studies. The analysis comparing rates of neurological decline was underpowered due to the relatively low event rates, and this is evident in that the LP group had over twice the rate of neurological decline as the fusion group, yet this was not statistically significant. Despite these limitations, this paper makes it clear that OPLL progression is much more common after LP than fusion (8-fold more common in this analysis). The more important question that was not answered was whether or not this is clinically meaningful. Given that the rate of neurological decline was twice as high in the LP group, it suggests that progression may have negative consequences in some patients. The authors’ conclusion that LP may be favored in elderly, low demand patients with medical comorbidities seems reasonable, while LF may be better for the younger, healthier patients. An RCT with long-term follow-up would be necessary to determine the answer to this question definitively.

Please read Dr. Lee’s article in the June 15 issue. Does this change your view of laminoplasty for OPLL? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor


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.