Thresholding approaches for estimating paraspinal muscle fat infiltration using T1- and T2-weighted MRI: Comparative analysis using water-fat MRI.

Background: Paraspinal muscle fat infiltration is associated with spinal degeneration and low back pain, however, quantifying muscle fat using clinical magnetic resonance imaging (MRI) techniques continues to be a challenge. Advanced MRI techniques, including chemical-shift encoding (CSE) based water-fat MRI, enable accurate measurement of muscle fat, but such techniques are not widely available in routine clinical practice. Methods: To facilitate assessment of paraspinal muscle fat using clinical imaging, we compared four thresholding approaches for estimating muscle fat fraction (FF) using T1- and T2-weighted images, with measurements from water-fat MRI as the ground truth: Gaussian thresholding, Otsu's method, K-mean clustering, and quadratic discriminant analysis. Pearson's correlation coefficients (r), mean absolute errors, and mean bias errors were calculated for FF estimates from T1- and T2-weighted MRI with water-fat MRI for the lumbar multifidus (MF), erector spinae (ES), quadratus lumborum (QL), and psoas (PS), and for all muscles combined. Results: We found that for all muscles combined, FF measurements from T1- and T2-weighted images were strongly positively correlated with measurements from the water-fat images for all thresholding techniques (r = 0.70-0.86, p < 0.0001) and that variations in inter-muscle correlation strength were much greater than variations in inter-method correlation strength. Conclusion: We conclude that muscle FF can be quantified using thresholded T1- and T2-weighted MRI images with relatively low bias and absolute error in relation to water-fat MRI, particularly in the MF and ES, and the choice of thresholding technique should depend on the muscle and clinical MRI sequence of interest.

Spatial distribution of fat infiltration within the paraspinal muscles: implications for chronic low back pain.

PURPOSE: Fat infiltration (FI) of the paraspinal muscles (PSMs) measured using MRI is an aspect of muscle quality and is considered to be worse in chronic low back pain (cLBP) patients. However, there is not a clear association between paraspinal muscle FI and cLBP, leaving the clinical importance of paraspinal muscle composition unestablished. The spatial distribution of FI in the PSMs may inform mechanistic understanding of non-specific cLBP as it relates to degenerative intervertebral disc (IVD) pathology. We hypothesized that paraspinal muscle fat-mapping would reveal distinct FI distribution patterns in relation to cLBP symptoms and proximity to symptomatic IVD degeneration. METHODS: From advanced-sequence water-fat MRI of 40 axial cLBP patients and 21 controls, we examined the spatial distribution of paraspinal muscle FI in relation to the center of rotation at the L4L5 disc. Using statistical parametric mapping, we compared FI patterns for multifidus (MF), erector spinae (ES), and psoas between patients and controls, and to the presence and severity of adjacent degenerative IVD pathology. RESULTS: The spatial distribution of PSMs FI differs between PSMs and according to symptoms and the adjacent degenerative IVD pathology. Furthermore, the region of MF closest to the disc center of rotation appears most susceptible to FI in the presence of symptomatic IVD degeneration. CONCLUSION: Our study identified spatial distribution patterns of FI in the PSMs as a potential diagnostic biomarker that may also provide granular mechanistic insights into spine biomechanics related to cLBP, as well as advancing the use of prior summary measures limited to overall muscle FI.

Compensatory biomechanics and spinal loading during dynamic maneuvers in patients with chronic low back pain.

PURPOSE: This study explores the biomechanics underlying the sit-to-stand (STS) functional maneuver in chronic LBP patients to understand how different spinal disorders and levels of pain severity relate to unique compensatory biomechanical behaviors. This work stands to further our understanding of the relationship between spinal loading and symptoms in LBP patients. METHODS: We collected in-clinic motion data from 44 non-specific LBP (NS-LBP) and 42 spinal deformity LBP (SD-LBP) patients during routine clinical visits. An RGB-depth camera tracked 3D joint positions from the frontal view during unassisted, repeated STS maneuvers. Patient-reported outcomes (PROs) for back pain (VAS) and low back disability (ODI) were collected during the same clinical visit. RESULTS: Between patient groups, SD-LBP patients had 14.3% greater dynamic sagittal vertical alignment (dSVA) and 10.1% greater peak spine torque compared to NS-LBP patients (p < 0.001). SD-LBP patients also had 11.8% greater hip torque (p < 0.001) and 86.7% greater knee torque (p = 0.04) compared to NS-LBP patients. There were no significant differences between patient groups in regard to anterior or vertical torso velocities, but anterior and vertical torso velocities correlated with both VAS (r = - 0.38, p < 0.001) and ODI (r = - 0.29, p = 0.01). PROs did not correlate with other variables. CONCLUSION: Patients with LBP differ in movement biomechanics during an STS transfer as severity of symptoms may relate to different compensatory strategies that affect spinal loading. Further research aims to establish relationships between movement and PROs and to inform targeted rehabilitation approaches.

Biomechanical changes in the lumbar spine following spaceflight and factors associated with postspaceflight disc herniation.

BACKGROUND CONTEXT: For chronic low back pain, the causal mechanisms between pathological features from imaging and patient symptoms are unclear. For instance, disc herniations can often be present without symptoms. There remains a need for improved knowledge of the pathophysiological mechanisms that explore spinal tissue damage and clinical manifestations of pain and disability. Spaceflight and astronaut health provides a rare opportunity to study potential low back pain mechanisms longitudinally. Spaceflight disrupts diurnal loading on the spine and several lines of evidence indicate that astronauts are at a heightened risk for low back pain and disc herniation following spaceflight. PURPOSE: To examine the relationship between prolonged exposure to microgravity and the elevated incidence of postflight disc herniation, we conducted a longitudinal study to track the spinal health of twelve NASA astronauts before and after approximately 6 months in space. We hypothesize that the incidence of postflight disc herniation and low back complaints associates with spaceflight-included muscle atrophy and pre-existing spinal pathology. STUDY DESIGN: This is a prospective longitudinal study. PATIENT SAMPLE: Our sample included a cohort of twelve astronaut crewmembers. OUTCOME MEASURES: From 3T MRI, we quantified disc water content (ms), disc degeneration (Pfirrmann grade), vertebral endplate irregularities, facet arthropathy and/ fluid, high intensity zones, disc herniation, multifidus total cross-sectional area (cm2), multifidus lean muscle cross-sectional area (cm2), and muscle quality/composition (%). From quantitative fluoroscopy we quantified, maximum flexion-extension ROM (°), maximum lateral bending ROM (°), and maximum translation (%). Lastly, patient outcomes and clinical notes were used for identifying postflight symptoms associated with disc herniations from 3T MRI. METHODS: Advanced imaging data from 3T MRI were collected at three separate time points in relation to spending six months in space: (1) within a year before launch ("pre-flight"), (2) within a week after return to Earth ("post-flight"), and (3) between 1 and 2 months after return to Earth ("recovery"). Fluoroscopy of segmental kinematics was collected at preflight and postflight timepoints. We assessed the effect of spaceflight and postflight recovery on longitudinal changes in spinal structure and function, as well as differences between crew members who did and did not present a symptomatic disc herniation following spaceflight. RESULTS: Half of our astronauts (n=6) experienced new symptoms associated with a new or previously asymptomatic lumbar disc protrusion or extrusion following spaceflight. We observed decreased multifidus muscle quality following spaceflight in the lower lumbar spine, with a reduced percentage of lean muscle at L4L5 (-6.2%, p=.009) and L5S1 (-7.0%, p=.006) associated with the incidence of new disc herniation. Additionally, we observed reduced lumbar segment flexion-extension ROM for L2L3 (-17.2%, p=.006) and L3L4 (-20.5%, p=.02) following spaceflight, and furthermore that reduced ROM among the upper three lumbar segments (-24.1%, p=.01) associated with the incidence of disc herniation. Existing endplate pathology was most prevalent in the upper lumbar spine and associated with reduced segmental ROM (-20.5%, p=.02). CONCLUSIONS: In conclusion from a 10-year study investigating the effects of spaceflight on the lumbar spine and risk for disc herniation, we found the incidence of lumbar disc herniation following spaceflight associates with compromised multifidus muscle quality and spinal segment kinematics, as well as pre-existing spinal endplate irregularities. These findings suggest differential effects of spinal stiffness and muscle loss in the upper versus lower lumbar spine regions that may specifically provoke risk for symptomatic disc herniation in the lower lumbar spine following spaceflight. Results from this study provide a unique longitudinal assessment of mechanisms and possible risk factors for developing disc herniations and related low back pain. Furthermore, these findings will help inform physiologic countermeasures to maintain spinal health in astronauts during long-duration missions in space.

Surgical site infections in pediatric spinal surgery after implementation of a quality assurance program.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To assess the effectiveness of two infection-reducing programs in mitigating the incidence of post-operative surgical site infections (SSI) in pediatric patients after spinal deformity surgery at our institution. Infections following spinal deformity surgery are associated with higher morbidity as well as significantly increased healthcare costs. SSI in patients with neuromuscular etiologies is especially high, exceeding 8 percent for myelodysplasia patients and 6 percent for cerebral palsy patients. METHODS: Manual chart review was conducted for 1934 pediatric spine procedures in 1200 patients at our institution between 2008 and 2018. Patients between the ages of 0 and 21 having any spinal surgical procedure including lengthening of growing rods were included. RESULTS: Institution of two separate infection-reducing programs reduced risk of SSI in this population by 65.4%, when adjusted for age and number of instrumentation levels (risk ratio [RR] = 0.3, 95% confidence interval [CI] = 0.2; 0.6, p = 0.001). Patients undergoing Initial Instrumentation demonstrated 68.8% less risk of SSI compared to those who had other types of surgical procedures, after adjusting for age and the number of level instrumented (RR = 0.3, 95% CI 0.2; .6, p = 0.002). It was observed that the effect of each of these infection-reducing programs diminished with time. This effect was also observed with prior programs implemented at our institution. CONCLUSION: The incidence of SSI decreased following the implementation of two infection-reducing programs especially in patients undergoing Initial Instrumentation procedures. However, time-series analysis suggests these programs may have maximal effect immediately following institution that diminishes with time. LEVEL OF EVIDENCE: Level III.

Ankle Fractures: The Current State of Online Patient Information.

Background. We assessed the quality, accuracy, and readability of websites for ankle fractures. Methods. Ankle Fracture, Broken Ankle, and Fibular Fracture were entered into 3 search engines. The first 25 results from each search were collected. Quality, accuracy, and readability were assessed by a custom rubric, 3 surgeons, and Fleisch-Kincaid grade level (FKGL), respectively. Results. A total of 57 websites were included: 24 were assigned to Ankle Fracture, 26 to Broken Ankle, and 7 to Fibular Fracture. The average quality score out of 36, accuracy score out of 12, and FKGL for all websites were 13.1 ± 6.8, 10.8 ± 1.2, and 9.6 ± 1.7, respectively. Websites assigned to the term Broken Ankle had a significantly lower New Dale-Chall score. Websites of lower FKGL and appearing earlier in results had significantly higher quality scores. Physician specialty societies (PSSs) had a significantly lower FKGL than websites of other types. Conclusion. The readability of patient materials is above the recommended level for ankle fractures. Encouragingly, a trade-off between readability and quality was not found. Patients should use search terms they are familiar with and prioritize websites that appear earlier in search results, are easier to read, and produced by PSSs.Level of Evidence: Level 3.

Kienböck Disease: Quality, Accuracy, and Readability of Online Information.

Background: Patients with limited health literacy require online educational materials to be written below a sixth grade level for optimal understanding. We assessed the quality, accuracy, and readability of online materials for Kienböck disease (KD). Methods: "Kienbock's Disease" and "Lunate Avacular Necrosis" were entered into 3 search engines. The first 25 Web sites from each search were collected. Quality was assessed via a custom grading rubric, accuracy by 2 residents and a fellow, and readability by Flesch-Kincaid grade level (FKGL) and New Dale-Chall test. Web sites were stratified according to the search term, FKGL, order of appearance, and authorship type. Results: A total of 38 unique Web sites were included, of which 22 were assigned to "KD" and 16 to "Lunate Avascular Necrosis." The average quality score out of 30, accuracy score out of 12, and FKGL for all Web sites were 13.3 ± 7.3, 10.4 ± 1.9, and 10.5 ± 1.4, respectively. Web sites assigned to the term "Kienbock's Disease" had a significantly higher FKGL. Web sites of higher FKGL had significantly worse accuracy scores. Order of appearance had no influence. Physician specialty societies (PSS) had a significantly lower FKGL than Web sites of other authorship types. Conclusions: Despite concerted efforts by national organizations, the readability of online patient materials is above the recommended level for KD. Patients with limited health literacy will be most affected by this reality. Until readability improves, patients should continue to consult their physicians when uncertain and prioritize Web sites that are easier to read and produced by PSS.