In the final NASS 2017 Best Paper session, investigators will present seven of this year’s top-rated abstracts, including studies exploring the association between adherence to appropriate use criteria and postoperative outcome in lumbar degenerative spondylolisthesis patients, the effect of lumbar spinal fusion on adjacent segment discs, and the viability of surgical intervention as an option for treatment of unstable type II odontoid fractures in patients 80 years of age or greater.
The Scientific Program Committee received more than 1,000 abstract and session proposal submissions for this year’s Annual Meeting in Orlando. From those accepted, the 21 highest rated abstracts will be presented during three separate Best Paper sessions on Wednesday, Thursday and Friday mornings at NASS 2017.
Following are previews of the Best Papers that will be presented on Friday, October 27. Visit the July e-preview for previews of the Wednesday, October 25 Best Papers. Visit the August e-preview for previews of the Thursday, October 26 Best Papers.
BEST PAPERS – FRIDAY, OCTOBER 27, 2017
Association between Adherence to Appropriate Use Criteria and Postoperative Outcome in Patients Treated For Lumbar Degenerative Spondylolisthesis
Presenting author: Francois Porchet, MD
The outcome of surgery for lumbar degenerative spondylolisthesis (LDS) is not always satisfactory and failures may be attributable to poor patient selection and the inappropriate use of surgical treatment. Appropriate Use Criteria (AUC) serve to help clarify the indications for a procedure and assist in identifying whether patients should receive surgical or conservative treatment.
“AUC are developed by panels of experts who review the current evidence in the literature and combine this with their own expert opinion to produce simple algorithms for deciding who should or should not have a certain treatment,” said Francois Porchet, MD.
In this study, Dr. Porchet and his colleagues used recently published AUC to carry out a retrospective evaluation of a large group of patients who had undergone surgery for LDS to determine the proportion of patients treated “appropriately” according to the criteria, and to evaluate whether surgical outcomes were better in patients for whom surgery was deemed “appropriate” compared with those for whom the criteria considered surgery to be “uncertain” or “inappropriate.”
Dr. Porchet reports that patients for whom surgery was deemed appropriate or uncertain had greater improvements in their patient-rated outcomes (measured with the Core Outcome Measures Index; COMI), ie their well being improved to a greater extent than patients for whom surgery was deemed inappropriate.
“The odds of these patients achieving a minimal clinically important change in their COMI score were three times greater,” Dr. Porchet said. “This provides support for the use of Appropriate Use Criteria in clinical practice. Such a tool should allow resources to be more focused, improving the overall level of care.”
Effect of Lumbar Spinal Fusion on Adjacent Segment Discs – An In Vivo Patient Study
Presenting author: Thomas D. Cha, MD, MBA
Lumbar fusion procedures aim to alleviate symptoms of lower back pain and neurologic symptoms from common degenerative disorders of the lumbar spine — including degenerative spondylolisthesis, spinal instability and discogenic back pain — when conservative measures fail.
“However, adjacent segment degeneration (ASD) remains a major concern post-fusion,” said Thomas D. Cha, MD, MBA. “Longitudinal radiographic studies show that 17% to 36% of patients warrant decompression or arthrodesis due to symptomatic degeneration within 5 to 10 years postoperatively.”
In this prospective longitudinal study, Dr. Cha and his colleagues investigated the effect of fusion surgery on ASD after a three-year follow-up using a precise and accurate in vivo imaging system under physiological weight-bearing conditions of the spine. Specifically, Pfirrmann grades, adjacent segment disc height, Cobb angle and range of motion were determined at the adjacent segment (L3-L4) before patients underwent a L4-S1 fusion and again at three years post-fusion follow-up. The results were compared with age-matched healthy control subjects to isolate the normal age-related changes to these factors.
“Using healthy subjects and the patient as their own control, it was determined that the adjacent segment disc height significantly decreased and the Pfirrmann grade significantly increased at three years post-fusion,” Dr. Cha said. “The loss of disc height can decrease the integrity of the discs and can lead to increased biomechanical stresses, which can accelerate disc degeneration. Therefore, this study elucidates the potential biomechanical mechanism of adjacent level degeneration in addition to the natural history of the adjacent disc after long-term follow up after lumbar fusion surgery.”
Adjacent Segment Degeneration after Lumbar Total Disc Replacement: 5-Year Results of a Multicenter, Prospective, Randomized Study with Independent Radiographic Assessment
Presenting author: Richard D. Guyer, MD
One potential benefit of lumbar total disc replacement (TDR) over fusion for the treatment of painful disc degeneration is the possibility of reducing adjacent segment degeneration (ASD); however, there has been little investigation into this area in large prospective studies.
“Our study is a post-hoc analysis of the activL IDE Trial,” said Richard D. Guyer, MD. “We were looking to determine the long-term rate of adjacent segment degeneration after lumbar total disc replacement to further support previous reports that have shown more than a three-fold reduced rate of adjacent segment disease at five years versus lumbar fusion.”
In this multicenter study, patients from 14 sites were enrolled, with 218 patients assigned to the investigational group, activL, and 106 assigned to the control group, ProDisc-L. All patients were treated for single-level symptomatic disc degeneration non-responsive to non-operative care. Measurements made from the radiographs included adjacent segment degeneration based in the Kellgren-Lawrence scale and the scale described by Zigler et al (J. Neuro Spine, 2012), range of motion, disc height and translation.
The results of this study corroborate previous findings suggesting that, by restoring motion and normal kinematics, disc replacement, unlike lumbar fusion, does not place excessive stresses on the adjacent segments.
“The motion preserved with current generations of lumbar disc replacements can lessen the rate of adjacent segment degeneration, thereby reducing the health care burden associated with degenerative disc disease,” Dr. Guyer said. “Just as no surgeon today would offer a hip fusion over a total joint replacement, we are slowly gathering substantial long-term data proving that, for the appropriately selected patient, disc arthroplasty should be a standard of care.”
Effect of L4-Sacrum Fusion Alignment on Biomechanics of the Proximal Lumbar Segments in Sitting Postures
Presenting author: Avinash G. Patwardhan, PhD
L4-sacrum is the most prevalent site of spinal fusions for painful degenerative conditions in adults. Even though adults spend increasing amounts of time sitting at work and home, the recommended lordosis angle across the fused segments is based on studies of standing alignment. The median number of hours spent sitting are as high as seven hours in an eight-hour work day for a wide variety of occupations, such as accountants, administrators, architects, truck drivers, software developers and analysts. Anecdotally, patients who have experienced no pain while sitting before surgery frequently report sitting intolerance and pain after fusion.
“The questions we looked to answer in this study were how different sitting postures alter the lumbosacral spinal alignment and what impact this has on the mechanical loading at proximal lumbar segments adjacent to L4-Sacrum fusion,” said Avinash G. Patwardhan, PhD. “Specifically, we sought to determine whether sitting postures after lumbar fusion surgery contribute to proximal junctional breakdown.”
In this study, postural influence on lumbosacral sagittal alignment was assessed by analyzing full-length radiographs of 11 asymptomatic volunteers taken in three postures: standing, erect-sitting and slumped-sitting. For each subject, the researchers numerically simulated the post-fusion postural compensation needed to accommodate sitting postures after L4-sacrum segments were immobilized duplicating their lordosis angle in the standing radiograph. The post-fusion accommodation was simulated by forcing the L1 vertebra to maintain its pre-fusion position and angular alignment, thereby maintaining the post-fusion alignment of the thoracic and cervical spine as near their pre-fusion alignment as possible.
“Our findings demonstrate that postural change from standing to sitting requires substantial flexion motion in L3-S1 segments and that fusing these segments in lordotic alignment duplicating the standing posture will require the adjacent segments to flex more to make up for this loss of mobility,” Dr. Patwardhan said. “The required compensation may lead to increased stresses at adjacent segments in post-fusion sitting postures and may explain sitting intolerance in some patients.”
High Rate of Intraoperative Monitoring (IOM) Alerts in 176 Severe Pediatric Deformity Patients and its Relationship to the Deformity Angularity Ratio (DAR)
Presenting author: Munish C. Gupta, MD
Severe pediatric deformity is technically challenging with higher complications. The purpose of this study was to determine the frequency of intraoperative monitoring changes during surgical correction of severe pediatric deformity and whether the changes are related to permanent neurological deficits.
In this study, researchers analyzed the data of 176 pediatric patients with severe deformity (≥100°) or who were scheduled for a vertebral column resection. Logistic regression was used to evaluate associations of different procedures and radiographic parameters with intraoperative neural monitoring alerts and postoperative deficits. All patients were followed for a minimum of two years.
Among their findings, the researchers report that 75 patients had a total of 114 intraoperative monitoring alerts. Sagittal deformity angularity ratio (DAR) was predictive for any intraoperative alert (p=0.04) and for transcranial electric motor evoked potentials (TCeMEP) (p=0.04). Coronal DAR was associated with somatosensory evoked potential (SSEP) alerts (p=0.02).
“Preoperatively, 161 patients were neurologically normal and 150 patients stayed normal postoperatively, while 11 had new neurological deficits,” said Munish C. Gupta, MD. “However, at two years postoperatively, 156 patients were normal and one of the 11 patients still had a deficit.”
Additionally, at two years, out of 14 neurologically abnormal patients preoperatively, 11 totally recovered, two partially recovered and one continued to have the preoperative deficit.
“In this high-risk population of severe deformity pediatric patients, there was a high incidence of intraoperative neural monitoring alerts; however, only two new permanent deficits were reported and 13 out of 14 patients improved or recovered from preoperative neurologic deficits,” Dr. Gupta said. “Sagittal DAR is associated with intraoperative monitoring alerts. Neural monitoring should be considered mandatory in these cases.”
The Feature of the Cardiac Function and Structure in Severe Thoracic Scoliokyphosis Patients — A Retrospective Study Based on the Echocardiographic and Holter Electrocardiograms
Presenting author: Yingsong Wang, MD
Patients with spinal deformity are often associated with chest deformity, especially in thoracic scoliosis. Recently, there has been quite a bit of research showing that thoracic scoliosis with chest deformity affects lung function, but few studies have focused on the impact on the heart.
“In our study, we wanted to evaluate cardiac function and structure in severe thoracic scoliokyphosis patients because data on the heart’s impact are quite rare,” said Yingsong Wang, MD.
A total of 72 severe thoracic scoliokyphosis with major curve (>90°) were included in the study; patients with cardiac disease and lung disease were excluded. Patients were divided into two subgroups according to the different directions of the major curve. Another 72 adolescent idiopathic scoliosis (AIS) patients with major curve were included in the study as control group. Cardiac function and structure were analyzed using echocardiographic and Holter electrocardiograms. Demographic traits — such age, sex, height and weight — and Cobb angle were also analyzed.
“We found that severe thoracic scoliokyphosis has a limited effect on cardiac function and structure; although left major curve can affect the cardiac structure to some extent,” Dr. Wang said. “The real threat is the poor lung function in severe thoracic scoliokyphosis.”
Mortality Rates Following Posterior C1-2 Fusion for Treatment of Displaced Type II Odontoid Fractures in Octogenarians: A 10-Year Review
Presenting author: Stephen Clark, MD
The treatment of unstable Type II odontoid fractures in elderly patients can present challenges. In patients older than 80 years, recent evidence indicates posterior C1-2 fusion resulted in improved survival as compared to other modes of treatment. This study aimed to analyze 30-day and one-year mortality rates, as well as the most common complications associated with posterior C1-2 fusion, to determine if surgical intervention is a viable option for treatment of unstable Type II odontoid fractures in patients 80 years of age or greater.
This retrospective analysis included 41 consecutive patients who underwent posterior C1-C2 fusion for management of unstable Type II odontoid fracture by four fellowship-trained spine surgeons at a single institution between January 2006 and June 2016. Fall from standing accounted for 40 of 41 fractures with the other due to motor vehicle collision. One patient had a neurologic deficit upon presentation. For statistical analysis, Fischer’s Exact test and logistic regression analysis were performed.
Based on their findings, the investigators in this study report that posterior C1-2 fusion results in lower mortality rate in octogenarians with displaced and/or angulated Type II odontoid fracture. The initial fracture displacement and postoperative dysphagia are associated with higher mortality rate in this patient population.