Faculty Bibliography

BACKGROUND CONTEXT:T1 slope is a novel thoracic parameter used to assess cervical spine sagittal balance. Thoracic index (TI) parameters including T1 slope and cervical sagittal alignment parameters may play an important role in degenerative cervical spondylolisthesis (DCS). Current literature regarding the relationship between TI and cervical sagittal alignment parameters in patients with DCS is limited. PURPOSE:(1) To evaluate the T1 slope, cervical sagittal alignment, and thoracic inlet parameter in patients with DCS using kinematic magnetic resonance imaging (kMRI), and (2) to find a correlation between the T1 slope, TI, and other cervical sagittal parameters in patients with DCS. DESIGN/SETTING:Retrospective kMRI study, Level III. PATIENT SAMPLE:Fifty-two patients with DCS from 1,128 patients from a cervical kMRI database. OUTCOME MEASURES:T1 slope, C2-C7 angle, sagittal vertical axis C2-C7 (SVA C2-C7), cranial tilt, cervical tilt, neck tilt, and thoracic inlet angle (TIA). METHODS:Cervical spine kMRIs of 52 patients with DCS (mean age 51.7±standard deviation) were analyzed in neutral, flexion, and extension positions. Patients with DCS were divided into two groups: anterolisthesis (N=33) and retrolisthesis (N=19). Each listhesis group was subclassified into grade 1 (slip 2-3 mm) and grade 2 (slip>3 mm). RESULTS:Grade 2 retrolisthesis had the largest T1 slope followed by grade 1 retrolisthesis, grade 2 anterolisthesis, and grade 1 anterolisthesis. Significant differences were found between the anterolisthesis and the retrolisthesis groups in the neutral position (p=.025). The flexion position had the largest T1 slope and showed a significant difference with anterolisthesis in the neutral position (p=.041). Sagittal vertical axis C2-C7 showed strong correlation with cranial tilt in all DCS groups and all positions. CONCLUSIONS:In our study, T1 slope was larger in grade 2 DCS, and the retrolisthesis group had larger T1 slope than the anterolisthesis group. Presence of larger T1 slope was significantly correlated with larger cervical lordosis curvature. Furthermore, cranial tilt was strongly correlated with SVA C2-C7.

PURPOSE/OBJECTIVE:To investigate the relationship between the facet fluid sign (FFS) and kinematics of affected lumbar segment in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinematic magnetic resonance imaging (kMRI).Materials and methods Ninety-two patients diagnosed with low-grade (Grade 1 or 2), single level lumbar degenerative spondylolisthesis L3 to S1. Angular and translational motion, whole lumbar motion, slip percentage, and facet angle were measured. Disc degeneration and degrees of osteoarthritis were graded, facet effusion was evaluated and classified as Positive or Negative FFS (PosFFS or NegFFS).Results There were significant differences in the facet degeneration, translational motion, percentage of total angular motion, and flexion-extension slip difference between the PosFFS and NegFFS group. 28.3% of the patients in PosFFS group had anterolisthesis in flexion, but not extension.There was a significant difference in the incidence of FFS between the dynamic and static spondylolisthesis (75% vs 35%, p < 0.001). If FFS was present on kMRI, a positive predictive value for dynamic spondylolisthesis was 75.6%. with the sensitivity and specificity of 0.75 and 0.65 for posFFS to diagnose dynamic DS. The likelihood ratio for dynamic slips in the presence of FFS was 2.1, and the likelihood ratio for static slips in the presence of FFS was 1.1.Conclusion Facet fluid sign was present in weight-bearing neutral position, and the presence of FFS in kMRI increased the probability of having dynamic spondylolisthesis.

PURPOSE:To investigate the changes of lumbar neural foramina size during dynamic motion using positional MRI. METHODS:Two hundred and fifty neural foramina from 50 patients were analyzed. Lumbar foraminal height, width, and area parameters from L1 to S1 were evaluated for changes in extension, neutral, and flexion positions on T2 parasagittal positional MRI images, and were correlated to lumbar angular motion. One-way analysis of variance (ANOVA) and post hoc analysis were used to examine the differences between levels and positions. RESULTS:Compared to the neutral position, almost all lumbar foraminal parameters (height, width at inferior level, and area) increased in flexion and decreased in extension at all levels, except for L5-S1 foraminal width at superior and middle levels. The foraminal height and area in all lumbar segments except L5-S1 increased as the lumbar angular motion changed from extension to flexion in <40° group. The foraminal width increased significantly at L3-4 and L4-5 among all groups. CONCLUSION:Lumbar foraminal dimensions increased in flexion compared to neutral and extension positions. Lumbar angular motion contributed to the changes of foraminal height and area at most of the segments, while it affected foraminal width only at L3-4 and L4-5. This information can be useful in the understanding of patient symptoms and the correlation with the imaging studies with dynamic foraminal stenosis. Furthermore, data from our study may help with patient positioning for foraminal injections or endoscopic surgery.

STUDY DESIGN/METHODS:A retrospective database study. OBJECTIVE:The goal of this study was to (1) evaluate the trends in the use of electromyography (EMG) for instrumented posterolateral lumbar fusions (PLFs) in the United States and (2) assess the risk of neurological injury following PLFs with and without EMG. SUMMARY OF BACKGROUND DATA/BACKGROUND:Neurologic injuries from iatrogenic pedicle wall breaches during screw placement are known complications of PLFs. The routine use of intraoperative neuromonitoring (ION) such as EMG during PLF to improve the accuracy and safety of pedicle screw implantation remains controversial. METHODS:A retrospective review was performed using the PearlDiver Database to identify patients who had PLF surgery with and without EMG for lumbar disorders from years 2007 to 2015. Patients undergoing concomitant interbody fusions or spinal deformity surgery were excluded. Demographic trends and risk of neurological injuries were assessed. RESULTS:During the study period, 2007 to 2015, 9957 patients underwent PLFs. Overall, EMG was used in 2495 (25.1%) of these patients. There was a steady increase in the use of EMG from 14.9% in 2007 to 28.7% in 2009, followed by a steady decrease to 21.9% in 2015 (P < 0.0001). The risk of postoperative neurological injuries following PLFs was 1.35% (134/9957) with a risk of 1.36% (34/2495) with EMG and 1.34% (100/7462) without EMG (P = 0.932). EMG is used most commonly for PLFs in the Southern part of the United States. CONCLUSION/CONCLUSIONS:In this retrospective national database review, we found that there was a steady increase in the routine use of EMG for PLFs followed by a steady decline. Regional differences were observed in the utility of EMG for PLFs. The risk of neurological complications following PLF in the absence of spinal deformity is low and the routine use of EMG for PLF may not decrease the risk. LEVEL OF EVIDENCE/METHODS:4.

PURPOSE/OBJECTIVE:To investigate the change of conus medullaris termination (CMT) level in neutral, flexion and extension positions and to analyze the effects of age and gender on the CMT level. METHODS:The midline sagittal T2-weighted kinetic magnetic resonance imaging (kMRI) study of 585 patients was retrospectively reviewed to identify the level of CMT. All patients were in an upright position. A straight line perpendicular to the long axis of the cord was drawn from the tip of the cord and then subtended to the adjacent vertebra or disk space. The CMT level was labeled in relation to the upper, middle and lower segments of adjacent vertebra or disk space and assigned values from 0 to 12 [0 = upper third of T12 (T12U), and 12 = upper third of L3 (L3U)]. All parameters were collected for neutral, flexion and extension positions. RESULTS:The level of CMT had the highest incidence (17.61%) at L1 lower (L1L) in neutral position, 17.44% at L1 upper (L1U) in flexion, and 16.92% at L1 middle (L1M) in extension with no significant differences among three positions (p > 0.05) in weight-bearing status. Moreover, the level of CMT was not correlated with age (p > 0.05). In terms of gender, the level of CMT was lower in women than in men in neutral position, flexion, and extension (p < 0.05). Furthermore, when divided by age in decades, there was a significant difference between females and males in the age group 60-69 years in neutral, flexion and extension position, respectively (p < 0.05). CONCLUSIONS:The level of CMT in the neutral position was in accordance with previous cadaveric and supine-position MRI studies, and it did not change with flexion and extension. Women had lower CMT level than men, especially in the older population. This information can be very valuable when performing spinal anesthesia and spinal punctures.

Animal and human studies demonstrate the anabolic properties of low-magnitude mechanical stimulation (LMMS) in its ability to improve bone formation by enhancing the proliferation of mesenchymal stem cells and their subsequent commitment down an osteoblastic lineage. Response to mechanical strains as low as 10μɛ have been seen, illustrating the sensitivity of mechanosensory cells to mechanotransduction pathways. Applications to the spine include treatment of osteoporosis in preparation for instrumented fusion, fracture reduction in spinal cord injury patients to slow bone mineral density loss, and bone tissue engineering and enhancement of bone-implant osseointegration for pseudarthrosis and hardware failure. This review provides an overview of the fundamentals of LMMS, highlights the cellular basis and biomechanics of how mechanical strain is translated into bone formation, and then discusses current and potential applications of these concepts to spinal disorders. Mechanical signals represent a key regulatory mechanism in the maintenance and formation of bone. Developing practical clinical applications of these mechanotransduction pathways continues to be an important area of investigation in its relation to spinal pathology.

STUDY DESIGN/METHODS:Retrospective analysis of a nationwide private insurance database. Chi-square analysis and linear regression models were utilized for outcome measures. PURPOSE/OBJECTIVE:The purpose of this study was to investigate any relationship between lumbar degenerative disc disease, diabetes, obesity and smoking tobacco. OVERVIEW OF LITERATURE/BACKGROUND:Diabetes, obesity, and smoking tobacco are comorbid conditions known to individually have effect on degenerative disc disease. Most studies have only been on a small populous scale. No study has yet to investigate the combination of these conditions within a large patient cohort nor have they reviewed the combination of these conditions on degenerative disc disease. METHODS:A retrospective analysis of insurance billing codes within the nationwide Humana insurance database was performed, using PearlDiver software (PearlDiver, Inc., Fort Wayne, IN, USA), to identify trends among patients diagnosed with lumbar disc degenerative disease with and without the associated comorbidities of obesity, diabetes, and/or smoking tobacco. Patients billed for a comorbidity diagnosis on the same patient record as the lumbar disc degenerative disease diagnosis were compared over time to patients billed for lumbar disc degenerative disease without a comorbidity. There were no sources of funding for this manuscript and no conflicts of interest. RESULTS:<0.05). CONCLUSIONS:Diabetes, obesity and cigarette smoking each are significantly associated with an increased diagnosis of lumbar degenerative disc disease. The combination of smoking and obesity had a synergistic effect on increased rates of lumbar degenerative disc disease. Patient education and preventative care is a vital goal in prevention of degenerative disc disease within the general population.

STUDY DESIGN/METHODS:Retrospective database review. OBJECTIVE:To analyze and report the trends and cost of posterior cervical fusions (PCFs) with and without off-label recombinant human bone morphogenetic protein-2 (rhBMP-2) in the Medicare population. METHODS:Patient records from the PearlDiver database were retrospectively reviewed from January 1, 2005, to December 31, 2012, to distinguish individuals who underwent a PCF with or without rhBMP-2. Total numbers, incidence, age, gender, geographic region, reimbursement, and length of stay were analyzed and summarized. RESULTS:The combined total of non-rhBMP-2 (n = 39 479; 85.51%) and rhBMP-2 PCF (n = 6692; 14.49%) procedures performed between 2005 and 2012 was 46 171. In general, the number of PCFs without rhBMP-2 consistently increased over time, while the number of PCFs with rhBMP-2 had only a slight increase from 2005 to 2012. On average, PCFs without rhBMP-2 were associated with $1197 higher cost than those with rhBMP-2, but the average length of stay was similar (6 days). From 2005 to 2012, the average cost for procedures with and without rhBMP-2 increased by $12 605 and $7291, respectively. The percentage of rhBMP-2 use peaked in 2007 and dwindled until 2010, and declined an additional 2.84% from 2011 to 2012. Multiple age, region, and gender tendencies were observed. CONCLUSIONS:To our knowledge, this was the first study to use the PearlDiver database to report incidence and cost trends of PCF procedures. This article provides meaningful trend data on PCFs to surgeons and clinicians, researchers, and patients, as well as functions as a beacon for future research questions.

STUDY DESIGN/METHODS:Retrospective analysis of national insurance billing database. OBJECTIVE:To examine trends in reoperation after single-level lumbar discectomy. SUMMARY OF BACKGROUND DATA/BACKGROUND:Lumbar discectomy is the most commonly performed procedure for treatment of radiculopathy caused by disc herniation. Randomized clinical trials have demonstrated the advantage of discectomy over nonsurgical treatment options, allowing for a more rapid reduction in symptoms. However, population-level data regarding reoperation after single level discectomy is limited. METHODS:Data were collected using the commercially available PearlDiver software for patients billed with the Current Procedural Terminology code for our index procedure, hemilaminotomy and removal of disc material, between January 2007 and September 2014. The index group was then followed for up to 4 years for recurrent lumbar surgery, including spinal fusion, laminectomy, and additional discectomy. RESULTS:Analysis of data obtained from 13,654 patient records revealed a rate of additional lumbar surgeries after single-level discectomy of 3.95% (539/13654) within 3 months and 12.2% (766/6274) within 4 years of the index procedure. Lumbar spinal fusion was performed on 5.9% (370/6274) of patients within 4 years. Patients who received a re-exploration discectomy within 2 years of the index procedure went on to receive lumbar fusion at a rate of 38.4% (48/125) within the 4 years after the re-exploration discectomy. The average additional cost of lumbar reoperation, as measured by insurance reimbursement, was approximately $11,161 per-patient per year. CONCLUSION/CONCLUSIONS:We report an overall 4-year reoperation rate of 12.2% after single-level discectomy. In addition, we report a rate of progression to lumbar fusion following re-exploration discectomy of 38.4% within 4 years of reoperation. Further studies are needed regarding the best treatment algorithm in patients with reherniation or iatrogenic instability after lumbar discectomy. This study should enhance the shared decision making process by providing surgeons and patients with valuable data regarding the frequency and nature of reoperations after discectomy. LEVEL OF EVIDENCE/METHODS:3.

STUDY DESIGN/METHODS:A multicenter, retrospective review of C5 palsy after cervical spine surgery. OBJECTIVE:Postoperative C5 palsy is a known complication of cervical decompressive spinal surgery. The goal of this study was to review the incidence, patient characteristics, and outcome of C5 palsy in patients undergoing cervical spine surgery. METHODS:tests or Fisher exact tests for categorical variables. RESULTS:Of the 13 946 cases reviewed, 59 patients experienced a postoperative C5 palsy. The incidence rate across the 21 sites ranged from 0% to 2.5%. At most recent follow-up, 32 patients reported complete resolution of symptoms (54.2%), 15 had symptoms resolve with residual effects (25.4%), 10 patients did not recover (17.0%), and 2 were lost to follow-up (3.4%). CONCLUSION/CONCLUSIONS:C5 palsy occurred in all surgical approaches and across a variety of diagnoses. The majority of patients had full recovery or recovery with residual effects. This study represents the largest series of North American patients reviewed to date.