Kinetic magnetic resonance imaging analysis of lumbar segmental motion at levels adjacent to disc herniation.

PURPOSE: A retrospective radiographic study was carried out to analyze the effect of lumbar disc herniation on the kinetic motion of adjacent segments. METHODS: A total of 162 patients with low back pain or radicular pain in the lower limbs without a prior history of surgery were evaluated using kinetic magnetic resonance imaging. Translational motion, angular variation, and disc height were measured at each segment from L1-L2 to L5-S1. Other factors including the degree of disc degeneration, age, gender, and vertebral segment location were analyzed to determine any predisposing risk factors for segmental instability adjacent to disc herniations. RESULTS: Spinal levels above the disc herniation exhibited, on average, a 6.4 % increase in translational motion per mm of disc herniation (P = 0.496) and a 21.4 % increase in angular motion per mm herniation (P = 0.447). Levels below the herniation demonstrated a 5.2 % increase in translational motion per mm of disc herniation (P = 0.428) and a decrease of 10.7 % in angular motion per mm (P = 0.726). The degree of disc degeneration had no significant correlation with adjacent level motion. Similarly, disc herniation was not significantly correlated with disc height at adjacent levels, although there was a significant relationship between gender and adjacent segment disc height. CONCLUSIONS: Although disc height, translational motion, and angular variation are significantly affected at the level of a disc herniation, no significant changes are apparent in adjacent segments. Our results indicate that herniated discs have no effect on range of motion at adjacent levels regardless of the degree of disc degeneration or the size of disc herniation, suggesting that the natural progression of disc degeneration and adjacent segment disease may be separate, unrelated processes within the lumbar spine.

Secreted phosphoprotein 24 kD (Spp24) inhibits growth of human pancreatic cancer cells caused by BMP-2.

The emerging role of bone morphogenetic proteins (BMPs) in the initiation and progression of multiple cancers has drawn great attention in cancer research. In this study, we report that BMP-2 can promote the proliferation of the pancreatic tumor cell line, PANC-1. Secreted phosphoprotein 24 kD (Spp24), a BMP binding protein, did not affect the proliferation of the cells but promoted the apoptosis of the cells in vitro. In a xeneograft tumor model using PANC-1 cells, BMP-2 dramatically promoted tumor growth, while Spp24 not only abolished the effect of BMP-2, but also dramatically induced tumor shrinking when used alone. Activation of Smad1/5/8 participated in this process as demonstrated by immunohistochemical staining of phosphorylated Smad 1/5/8. We conclude that Spp24 can be developed into a therapeutic agent that could be employed in clinical situations where the inhibition of BMPs and related proteins is advantageous.

The evaluation of cervical spine mobility without significant spondylosis by kMRI.

STUDY DESIGN: Retrospective analysis of kinetic magnetic resonance images (kMRI). OBJECTIVE: To analyse the kinematics of cervical spine inpatients without significant spondylosis and to understand the normal movement of the cervical spine as reference for future comparison. SUMMARY OF BACKGROUND DATA: Although some studies have been conducted to describe the normal mobility of the cervical spine, prior studies did not establish a relationship between the kinematics of cervical spine and disc degeneration. Only a few studies of the kinematics of the non-degenerated cervical spine have been reported; however, they focused on single level and not all the levels of cervical spine. METHODS: 468 symptomatic patients underwent upright cervical kMRI, and cervical disc degeneration was evaluated with a new grading system. This grading system consists of four grades (0-III), and the cervical spines with grade 0 and grade I discs were included in this study. Finally, 61 symptomatic patients were studied 34 male and 27 female with an average age of 41.9 years. kMRI was used to define the normal mobility of the cervical spine by calculating the translation motion, angular variation and percentage angular contribution to the total cervical spine. RESULTS: The translation motion of the cervical spine at each level was 0.85 ± 1.22 mm at C2/3, 1.05 ± 1.19 mm at C3/4, 0.63 ± 1.19 mm at C4/5, 0.57 ± 0.91 mm at C5/6, 0.16 ± 0.86 mm at C6/7 and -0.11 ± 0.81 at C7/T1. In general, the translation motion decreased from proximal segment to distal segment. The angular variation of the cervical spine at each level was 5.58 ± 3.86° at C2/3, 8.26 ± 4.81° at C3/4, 9.11 ± 4.87° at C4/5, 10.05 ± 5.26° at C5/6, 8.31 ± 4.30° at C6/7 and 4.87 ± 3.28° at C7/T1. The angular variation at C2/3 and C7/T1 was significantly lower compared to other levels (P < 0.05). The contribution of each cervical level to the total angular mobility of cervical spine was the greatest at C5/6 (21.68 ± 10.31%) and least at C7/T1 (11.11 ± 7.60%) (P < 0.05). CONCLUSION: This study demonstrates the normal cervical segmental mobility for the entire cervical spine using kMRI. These results will be helpful to understand the normal mobility of the cervical spine and for understanding the relationship between kinematics of the cervical spine and disc degeneration for future comparisons.

The effect of aging on posterior intertransverse lumbar fusion: a New Zealand white rabbit model.

STUDY DESIGN: In vivo assessment of lumbar spinal fusion between a younger and older cohort of New Zealand white rabbits. OBJECTIVE: Directly compare fusion within young and aged New Zealand white rabbits to establish an aged spinal fusion model translational research. SUMMARY OF BACKGROUND DATA: Prior studies have utilized skeletally mature young rabbits (6-12 mo old) that may not be appropriate as an analog for studying the aging human spine. METHODS: Ten aged (>36 mo old) and 10 young (12 mo old) New Zealand white rabbits underwent a single-level, bilateral, L5-6 posterolateral intertransverse fusion using autogenous iliac crest bone graft. The animals were killed at 6 weeks postoperatively, and the specimens were then evaluated with quantitative microcomputerized tomography and manual palpation by 6 orthopedic surgeons. The fusions were graded as either fused or not fused by each examiner. The spines were then embedded in poly(methyl methacrylate) and cut into 2-mm-thick sections for histologic analysis. RESULTS: A higher percentage of young rabbits were determined to be successfully fused through manual palpation testing compared with the aged rabbits. Micro-computed tomography (CT) analysis revealed a significantly greater fusion mass volume in the younger rabbits than in the older cohort. In addition, the fusion density of the younger rabbits was found to be significantly lower than that of the older rabbits when normalized to the bone density in the nonfused portion of the spine. Histologic analysis showed that the quality of the bone within the fusion mass was consistent between the young and old rabbits. A greater number of young animals had bilateral continuous bone graft compared with the aged animals. CONCLUSIONS: The aged (>36 mo) New Zealand white rabbit model appears to be a valid model to evaluate the effect of aging on lumbar fusion and has the potential to more accurately model conditions that are present in the older human spine.

The effect of bone morphogenetic protein-2 injection at different time points on intervertebral disk degeneration in a rat tail model.

STUDY DESIGN: Prospective in vivo rat tail model of disk degeneration comparing the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) injection over various time points and grades of degeneration. OBJECTIVE: To evaluate the effect of timing and disk grade on rhBMP-2 injection in a rat tail model of disk degeneration. SUMMARY OF BACKGROUND DATA: rhBMP-2 stimulates the proliferation of intervertebral disk cells and the secretion of extracellular matrix. However, few in vivo studies have demonstrated whether rhBMP-2 also improves disk degeneration and the severity of disk degeneration beyond which disks cannot be recovered by rhBMP-2 treatment. METHODS: Two coccygeal disks of each rodent subject were punctured percutaneously using an 18 G needle. At 4 weeks after the puncture, disks demonstrating induced degeneration were divided into 3 groups. Groups 1, 2, and 3 were treated with 7.5 µg rhBMP-2 or phosphate buffered saline by injection into the disk at 4, 6, and 8 weeks postpuncture, respectively. Plain radiographs and magnetic resonance images (MRIs) were obtained on the day of puncture and every 2 weeks thereafter until sacrifice. At 6 weeks after injection, each group was killed and examined with histologic and immunohistochemical analysis. RESULTS: According to MRI disk grade evaluation of the degenerative disk, rhBMP-2 significantly improved degeneration grade in group 1 at 2 weeks after injection. According to radiographic disk height index, groups 1 and 2 showed a trend toward improvement at 2 weeks after rhBMP-2 injection. Chondrogenic differentiation was noted on immunohistochemical staining of many disks treated with rhBMP-2. CONCLUSIONS: rhBMP-2 injection of degenerated disks at 4 weeks postpuncture induced a transient improvement in disk grade on MRI and stimulated chondrogenic differentiation. These data suggest rhBMP-2 as a potential therapy for degenerative disk disease.

Effect of Modic changes on spinal canal stenosis and segmental motion in cervical spine.

PURPOSE: Few studies have reported the characteristics of Modic changes (MCs) in the cervical spine in contrast to the lumbar spine. The purpose of this study was to identify the prevalence of MCs in the cervical spine and to elucidate the relationship of MCs with spinal canal stenosis and angular motion. METHODS: 437 consecutive, symptomatic patients with neck pain with or without neurogenic symptoms were included in this study. MRI in multiple positions was performed with dynamic motion of the cervical spine in upright, weight-bearing neutral, flexion and extension positions. Type of MC, intervertebral disc degeneration grade, spinal cord compression grade and sagittal angular motion between flexion and extension for each segment from C2-3 to C6-7 were evaluated. RESULTS: MCs were observed in 84 out of 437 patients (19.2%) and in 109 out of 2,185 motion segments (5.0%) with type 2 changes predominating. Disc degeneration grades and spinal cord compression grades of segments with MCs were significantly higher than those without MCs. Sagittal angular motion of segments with MCs were significantly lower than those without MCs. Multiple logistic regression analysis revealed that significantly elevated odds ratios for MCs were observed in segments with severe disc degeneration, severe spinal canal compression and less angular motion. CONCLUSION: The cervical segments with MCs were significantly more likely to have disc degeneration and spinal canal stenosis. In addition, the segments with MCs had significantly less angular motion, which suggests MCs may correlate with loss of mobility.

Missed cervical disc bulges diagnosed with kinematic magnetic resonance imaging.

PURPOSE: To determine if adding flexion and extension MRI studies to the traditional neutral views would be beneficial in the diagnosis of cervical disc bulges. METHODS: Five hundred patients underwent MRI in neutral, flexion and extension positions. The images were analyzed using computer software to objectively quantify the amount of disc bulge. RESULTS: Compared to the neutral position, cervical disc bulges were significantly increased in the extension position (P < 0.05), but on flexion position, there was no significant difference (P > 0.05). For patients without or <3 mm of disc bulge in neutral, 2.97% demonstrated an increase in bulge to ≥3 mm bulge in flexion, and 16.41% demonstrated an increase to ≥3 mm bulge in extension. For patients in the neutral view that had a baseline disc bulge of 3-5 mm, 3.73% had increased bulges to ≥5 mm in flexion and 11.57% had increased bulges to ≥5 mm in extension. CONCLUSION: A significant increase in the degree of cervical disc bulge was found by examining extension views when compared with neutral views alone. Kinematic MRI views provide valuable added information, especially in situations where symptomatic radiculopathy is present without any abnormalities demonstrated on traditional neutral MRI.

Secreted phosphoprotein 24 kD (Spp24) inhibits the growth of human osteosarcoma through the BMP-2/Smad signaling pathway.

Autocrine stimulation of tumor cells is an important mechanism for the growth of skeletal tumors. In tumors that are sensitive, growth factor inhibitors can dramatically reduce tumor growth. In this study, our aim was to investigate the effects of Secreted phosphoprotein 24 kD (Spp24) on the growth of osteosarcoma (OS) cells in the presence and absence of exogenous BMP-2 both in vitro and in vivo. Our study demonstrated that Spp24 inhibited proliferation and promoted apoptosis of OS cells as confirmed by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay and immunohistochemical staining. We found that BMP-2 increased the mobility and invasiveness of tumor cells in vitro whereas Spp24 inhibited both of these processes alone and in the presence of exogenous BMP-2. Phosphorylation of Smad1/5/8 and Smad8 gene expression was enhanced by treatment with BMP-2 but inhibited by treatment with Spp24. Subcutaneous and intratibial tumor models in nude mice demonstrated that BMP-2 promoted OS growth in vivo, while Spp24 significantly inhibited tumor growth. We conclude that the BMP-2/Smad signaling pathway is involved in the pathogenesis of OS growth and that Spp24 inhibits the growth of human OS induced by BMP-2 both in vitro and in vivo. Interruption of Smad signaling and increased apoptosis appear to be the primary mechanisms involved. These results confirm the potential of Spp24 as a therapeutic agent for the treatment of OS and other skeletal tumors.

Spinopelvic dissociation as a complication of iliac crest bone graft harvest using an acetabular reamer.

STUDY DESIGN: Descriptive case report. OBJECTIVE: To report spinopelvic dissociation as a complication of autogenous bone graft harvest with the use of an acetabular reamer. SUMMARY OF BACKGROUND DATA: Iliac crest bone graft harvest has been previously described in orthopedic literature with overall complication rates of 0% to 39%. Complications are inconsistently separated into "minor" and "major" groups, commonly reporting hematoma, infection, and injury to the superior gluteal artery or nerve. No reports of spinopelvic dissociation, a well known injury in the traumatic setting, have been reported. METHODS: We report the case of 1 patient who presented with spinopelvic dissociation after autogenous bone graft harvest with the use of an acetabular reamer. RESULTS: We present a unique case in which fracture through the reamer harvesting site led to complete disruption of the posterior pelvic ring on the operative side. Subsequent attempted closed management led to failure through the osteoporotic anterior pelvic ring on the operative side and the posterior pelvic ring on the contralateral side, leading to progressive instability, disability, and pain. This was successfully addressed with lumbopelvic fusion and 2-year follow-up is presented. CONCLUSIONS: The potential hazard of acetabular reamer bone graft harvest is discussed, and primary operative fixation of harvest-related fractures is suggested.

Patterns of Lumbar Disc Degeneration: Magnetic Resonance Imaging Analysis in Symptomatic Subjects.

STUDY DESIGN: Cross-sectional study. PURPOSE: To evaluate lumbar disc degeneration (LDD) on magnetic resonance imaging (MRI) in symptomatic subjects to accumulate baseline data on the pattern of degeneration. OVERVIEW OF LITERATURE: LDD plays an important role in the diagnosis and treatment of low-back pain in patients. Few studies have focused on the pattern of LDD to understand how the lumbar spine ages. METHODS: This study included 1,095 patients (mean age, 44.29 years; range, 16-85 years) who underwent upright lumbar MRI. LDD was graded into five categories (I-V). Positive LDD was defined as grade III or greater. The prevalence and pattern of LDD were analyzed, and the correlations between age and total grade of LDD were evaluated. RESULTS: The average number of LDD levels and the total grade of LDD increased with age. LDD moved cephalad with age. The rate of LDD increased rapidly during the decade before the prevalence of LDD and became >50%. In the single-level LDD group, the levels L5-S1 were the most common levels (60.3%). In the two-level group, L4-L5 and L5-S1 were the most common levels (53.5%). In the three-level group, L3-L4, L4-L5, and L5-S1 were the most common levels (55.7%). In the multilevel LDD group, contiguous multilevel disc degeneration (CMDD) was more common than the skipped level disc degeneration (SLDD). The levels L4-L5 were the most common levels in the CMDD group, and L5-S1 were the most common levels among SLDD. CONCLUSIONS: LDD was found to correlate with age, and the specific patterns and rates of LDD depended on lumbar disc level and age. These LDD pattern data can be used before spinal procedures to predict the probability of natural LDD progression with age.

Preoperative Maximization to Reduce Complications in Spinal Surgery.

STUDY DESIGN: Invited narrative review. OBJECTIVES: The aim of this review was to summarize current literature regarding risk factors that surgeons can optimize in the preoperative setting in the spinal surgery patient, in order to reduce complications and improve patient-reported outcomes. METHODS: Review of the relevant literature by the authors. RESULTS: Modifiable risk factors identified relative to the patient include obesity, malnutrition/nutrient deficiency, diabetes/hyperglycemia, preoperative anemia, vitamin D/DEXA (dual-energy radiograph absorptiometry), nicotine use/smoking, and opioid use/psychosocial factors. CONCLUSION: By maximizing a patient's physiological and psychological status prior to elective spine surgery, we may move closer to achieving the goals of value-based care: improving patient-reported outcomes while decreasing the cost of care.

Minimizing Blood Loss in Spine Surgery.

STUDY DESIGN: Broad narrative review. OBJECTIVE: To review and summarize the current literature on guidelines, outcomes, techniques and indications surrounding multiple modalities of minimizing blood loss in spine surgery. METHODS: A thorough review of peer-reviewed literature was performed on the guidelines, outcomes, techniques, and indications for multiple modalities of minimizing blood loss in spine surgery. RESULTS: There is a large body of literature that provides a consensus on guidelines regarding the appropriate timing of discontinuation of anticoagulation, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and herbal supplements prior to surgery. Additionally, there is a more heterogenous discussion the utility of preoperative autologous blood donation facilitated by erythropoietin and iron supplementation for healthy patients slated for procedures with high anticipated blood loss and for whom allogeneic transfusion is likely. Intraoperative maneuvers available to minimize blood loss include positioning and maintaining normothermia. Tranexamic acid (TXA), bipolar sealer electrocautery, and topical hemostatic agents, and hypotensive anesthesia (mean arterial pressure (MAP) <65 mm Hg) should be strongly considered in cases with larger exposures and higher anticipated blood loss. There is strong level 1 evidence for the use of TXA in spine surgery as it reduces the overall blood loss and transfusion requirements. CONCLUSION: As the volume and complexity of spinal procedures rise, intraoperative blood loss management has become a pivotal topic of research within the field. There are many tools for minimizing blood loss in patients undergoing spine surgery. The current literature supports combining techniques to use a cost- effective multimodal approach to minimize blood loss in the perioperative period.

Bone morphogenetic protein-2 promotes osteosarcoma growth by promoting epithelial-mesenchymal transition (EMT) through the Wnt/ß-catenin signaling pathway.

The correlation between BMP-2 and osteosarcoma growth has gained increased interest in the recent years, however, there is still no consensus. In this study, we tested the effects of BMP-2 on osteosarcoma cells through both in vitro and in vivo experiments. The effect of BMP-2 on the proliferation, migration and invasion of osteosarcoma cells was tested in vitro. Subcutaneous and intratibial tumor models were used for the in vivo experiments in nude mice. The effects of BMP-2 on EMT of osteosarcoma cells and the Wnt/ß-catenin signaling pathway were also tested using a variety of biochemical methods. In vitro tests did not show a significant effect of BMP-2 on tumor cell proliferation. However, BMP-2 increased the mobility of tumor cells and the invasion assay demonstrated that BMP-2 promoted invasion of osteosarcoma cells in vitro. In vivo animal study showed that BMP-2 dramatically enhanced tumor growth. We also found that BMP-2 induced EMT of osteosarcoma cells. The expression levels of Axin2 and Dkk-1 were both down regulated by BMP-2 treatment, while ß-catenin, c-myc and Cyclin-D1 were all upregulated. The expression of Wnt3α and p-GSK-3ß were also significantly upregulated indicating that the Wnt/ß-catenin signaling pathway was activated during the EMT of osteosarcoma driven by BMP-2. From this study, we can conclude that BMP-2 significantly promotes growth of osteosarcoma cells (143B, MG63), and enhances mobility and invasiveness of tumor cells as demonstrated in vitro. The underlying mechanism might be that BMP-2 promotes EMT of osteosarcoma through the Wnt/ß-catenin signaling pathway. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1638-1648, 2019.

Different Fusion Approaches for Single-level Lumbar Spondylolysis Have Similar Perioperative Outcomes.

STUDY DESIGN: Retrospective cohort study OBJECTIVE.: The aim of this study was to compare perioperative adverse events for patients with lumbar spondylolysis treated with transforaminal lumbar interbody fusion (TLIF), posterior spinal fusion (PSF), combined anterior and posterior fusion (AP fusion), or anterior lumbar interbody fusion (ALIF). SUMMARY OF BACKGROUND DATA: Previous cohort studies have shown similar long-term outcomes for different surgical approaches for this indication, but potential differences in 30-day perioperative adverse events have not been well characterized. METHODS: The present study uses data extracted from the American College of Surgeons National Surgical Quality Improvement Database. Patients undergoing fusion with different approaches for lumbar spondylolysis were identified. Propensity score matching was utilized to account for potential differences in demographic and comorbidity factors. Comparisons among perioperative outcomes were then made among the propensity score-matched study groups. RESULTS: Of 1077 cases of spondylolysis identified, 556 underwent TLIF, 327 underwent PSF, 108 underwent AP fusion, and 86 underwent ALIF. After propensity score matching, there were no differences in the rates of any of the 30-day individual adverse events studied and no differences in the aggregated groupings of any adverse event, serious adverse event, or minor adverse event. There was a significantly increased operative time in the AP fusion group, but there were no differences in hospital length of stay or readmission rates. CONCLUSION: Because perioperative adverse event rates were similar, even with a slightly longer operative time in the AP fusion group, these findings suggest that surgeon preference and long-term outcomes are better used to determine the recommendation of one surgical approach over another for single level fusions for lumbar spondylolysis. LEVEL OF EVIDENCE: 3.

Patterns of Cervical Disc Degeneration: Analysis of Magnetic Resonance Imaging of Over 1000 Symptomatic Subjects.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: The aim of this study was to evaluate cervical disc degeneration on magnetic resonance imaging (MRI) in a large population of symptomatic patients and to provide baseline data on the pattern of degeneration in order to understand how the cervical spine ages. METHODS: We performed a cross-sectional study of 1059 patients who underwent upright cervical MRI for neck pain with and without neurological symptoms. A total of 6354 cervical discs from C2/3 to C7/T1 were evaluated. Cervical disc degeneration was evaluated on T2-weighted MRI and graded into 4 categories (Grades 0-III). Positive degeneration was defined as greater than Grade II. The correlation between age and total grade of degeneration of each patient was evaluated, as well as the prevalence and pattern of degeneration. RESULTS: The average number of degenerated disc levels and the total grade of cervical disc degeneration significantly increase with age. In the patient group with 1-level degeneration, C5/6 was the most common degenerated level followed by C4/5 and C6/7. In the group with 2-level degeneration, C5/6 & C6/7 was most common followed by C4/5 & C5/6 and C3/4 & C4/5. Skip level degeneration was significantly rarer than contiguous level degeneration, and C7/T1 and C2/3 were the most unlikely to degenerate in multilevel degeneration. CONCLUSION: Disc degeneration is most common in the middle cervical spine (C5/6) and progresses to contiguous levels, except for C7/T1 and C2/3. This pattern may play a role in adjacent-level disc degeneration associated with spinal fusion.

How does sagittal imbalance affect the appropriateness of surgical indications and selection of procedure in the treatment of degenerative scoliosis? Findings from the RAND/UCLA Appropriate Use Criteria study.

BACKGROUND CONTEXT: Degenerative lumbar scoliosis (DLS) is often associated with sagittal imbalance, which may affect patients' health outcomes before and after surgery. The appropriateness of surgery and preferred operative approaches has not been examined in detail for patients with DLS and sagittal imbalance. PURPOSE: The goals of this article were to describe what is currently known about the relationship between sagittal imbalance and health outcomes among patients with DLS and to determine how indications for surgery in patients with DLS differ when sagittal imbalance is present. STUDY DESIGN/SETTING: This study included a literature review and an expert panel using the RAND/University of California at Los Angeles (UCLA) Appropriateness Method. METHODS: To develop appropriate use criteria for DLS, researchers at the RAND Corporation recently employed the RAND/UCLA Appropriateness Method, which involves a systematic review of the literature and multidisciplinary expert panel process. Experts reviewed a synopsis of published literature and rated the appropriateness of five common operative approaches for 260 different clinical scenarios. In the present work, we updated the literature review and compared panelists' ratings in scenarios where imbalance was present versus absent. This work was funded by the Collaborative Spine Research Foundation, a group of surgical specialty societies and device manufacturers. RESULTS: On the basis of 13 eligible studies that examined sagittal imbalance and outcomes in patients with DLS, imbalance was associated with worse functional status in the absence of surgery and worse symptoms and complications postoperatively. Panelists' ratings demonstrated a consistent pattern across the diverse clinical scenarios. In general, when imbalance was present, surgery was more likely to be appropriate or necessary, including in some situations where surgery would otherwise be inappropriate. For patients with moderate to severe symptoms and imbalance, a deformity correction procedure was usually appropriate and frequently necessary, except in some patients with severe risk factors for complications. Conversely, procedures that did not correct imbalance, when present, were usually inappropriate. CONCLUSIONS: Clinical experts agreed that sagittal imbalance is a major factor affecting both when surgery is appropriate and which type of procedure is preferred among patients with DLS.

Pedicle screw fixation (T1, T2, and T3).

The indications for thoracic pedicle screw fixation have expanded over the past decade. Thoracic pedicle screws are now being used in the treatment of degenerative, traumatic, neoplastic, congenital, and developmental disorders. The pedicles of T1, T2, and T3 are typically large and ovoid in shape and amenable to pedicle screw fixation in most instances. The placement of thoracic pedicle screws requires knowledge of the topographic and deep bony anatomy of the thoracic spine as well as an appreciation of the surrounding visceral structures at risk. With strict adherence to the surgical techniques of insertion, thoracic pedicle screw fixation is a safe and effective method of stabilization. It offers several advantages over other forms of fixation, especially in the upper thoracic spine where the options are limited.

Dynamic Evaluation of the Cervical Spine and the Spinal Cord of Symptomatic Patients Using a Kinetic Magnetic Resonance Imaging Technique.

PURPOSE: The purpose of this study was to examine the movement of the spinal cord and its relationship to the spinal canal in patients with mild spondylosis using kinetic magnetic resonance imaging (kMRI). METHODS: Weight-bearing, multiposition kMRI was performed on symptomatic patients through a full range of flexion-extension. A total of 52 study patients were selected based on the C2-C7 Cobb angle of sagittal alignment: lordotic (from 30 to 45 degrees). We evaluated dynamic changes in different parameters from flexion-extension: spinal canal diameter (CD), spinal cord diameter (SCD), space available for the cord, anterior space available for the cord (ASAC), posterior space available for the cord (PSAC), average distance between the anterior canal and the cord (d-value), and global angle for the spinal canal and cord. RESULTS: The CD tended to decrease from flexion to extension from C3/C4 to C6/C7, however, there were no significant differences at the proximal and distal levels, C2/C3 and C7/T1. There were no significant differences of SCD between different postures. The SCD tended to decrease from C2/C3 to C7/T1. The ASAC followed the same pattern as CD-values. The ASAC was narrowest at C4/C5 and C5/C6. The PSAC tended to increase from C2/C3 to C7/T1. The spinal cord shifted anteriorly with extension and posteriorly with flexion. In addition, the spinal cord maintained its curve with the movement. CONCLUSIONS: The kinematics of spinal cord motion may be associated with the pathogenesis of cervical spondylotic myelopathy. However, the spinal cord maintains its curve with position changes. Consequently, different motions of the cervical spine may affect spinal cord migration and cause changes in ASAC and PSAC.

Magnetic Resonance Classification System of Cervical Intervertebral Disk Degeneration: Its Validity and Meaning.

STUDY DESIGN: Retrospective analysis of kinetic magnetic resonance images (kMRIs). OBJECTIVE: (1) To analyze the changes seen on MRI related to disk degeneration and to develop a new grading system for cervical disk degeneration. (2) To evaluate the reliability and validity of the grading system. SUMMARY OF BACKGROUND DATA: Few have studied the relationship between changes seen on MRI with cervical disk degeneration and the chronological order of disk degeneration. A few grading systems for cervical disk degeneration have been reported; however, there have been problems related to subjectivity and lack of a clear, reliable algorithm. METHODS: A total of 300 cervical intervertebral disks were graded for nucleus color, structure, disk bulge, and disk height. On the basis of the analysis, a new grading system consisting of 4 grades (grade 0-III) and algorithm were developed. Intraobserver and interobserver reliabilities were assessed. A total of 2802 intervertebral disks were then evaluated using the grading system to correlate disk degeneration grades with patient age and function and to evaluate the validity of the new system. RESULTS: On the basis of cross-table analysis, disk degeneration presents in the following order: (1) decrease and/or change of nucleus intensity; (2) loss of distinction between nucleus and annulus; (3) positive disk bulge; and (4) disk height decrease. The κ-coefficients for intraobserver and interobserver agreements were 0.96 and 0.90, respectively. Severe disk degeneration is most common at C5/C6 followed by C6/C7 and C4/C5, and total disk degeneration grade is correlated with age (R=0.467). There was a decrease of angular motion in grades I-III and an increase in translational motion and decrease of space available for the cord in grades II-III. CONCLUSIONS: We developed a new classification system of cervical disk degeneration based on analysis of the changes seen on MRI. Reliability tests indicated high reproducibility of this system, and further analysis confirmed its validity and clinical significance.

Results of the 2015 Scoliosis Research Society Survey on Single Versus Dual Attending Surgeon Approach for Adult Spinal Deformity Surgery.

STUDY DESIGN: An electronic survey administered to Scoliosis Research Society (SRS) membership. OBJECTIVE: To characterize surgeon practices and views regarding the use of two attending surgeons for adult spinal deformity (ASD) surgery. SUMMARY OF BACKGROUND DATA: The use of two experienced attending surgeons can decrease the operative time, estimated blood loss, and perioperative complication rates. However, the current practice patterns for the use of two attending surgeons remains unknown. METHODS: An electronic, 27-question survey regarding single/dual attending surgeons was administered to the SRS membership. Determinants included: surgeon/practice demographics, assistant type/level of training, and questions regarding use of two attending surgeons. Overall reporting and comparisons between groups were made: US versus international, academic versus private practice, and experience <15 years versus >15 years. RESULTS: A total of 199 surgeons responded from 27 different countries. Overall and between the groups, the respondents significantly reported believing that two attending spine surgeons improves safety, decreases complications, and improves outcomes (P < 0.01). Approximately, 67.3% reported using a second attending ≤25% of the time (33.2% do not), and 24.1% use one ≥51% of the time (similar between groups); 51.1% that have a second attending feel it's limited by reimbursement and access concerns and 71.9% have difficulty getting the second attending reimbursed. 72.3% use a second attending for ALL of the following reasons (no difference between groups): "it's safer/reduces complications," "it decreases operative time," "it decreases blood loss," "it results in improved outcomes," "it's less work and stress for me." If reimbursement was equal/assured for a second attending, 67.5% would use one "more often" or "always." CONCLUSION: The respondents feel that having a second attending surgeon improves patient care, however most do not use one often. Reasons include reimbursement/access concerns and the majority would use one if reimbursement was equal and assured. Based on the current literature and these results, there is a need for working with third party payers to improve dual surgeon reimbursement rates in complex cases. LEVEL OF EVIDENCE: 5.