Coronal Orientation Research Articles

3D patient imaging and retrieval analysis help understand the clinical importance of rotation in knee replacements

PurposeThe purpose of the present study was to correlate highly accurate CT measurements of pre-revision total knee arthroplasty (TKA) implant position with findings of retrieval analysis post-revision, to understand the clinical relevance of TKA orientation.MethodsThis study involved 53 retrieved TKA implants with pre-revision 3D-CT scans used to determine coronal (varus–valgus), sagittal (tibial slope) and rotational (internal rotation–external rotation) TKA orientation as well as tibiofemoral leg axis. Differences between femoral and tibial angles to describe the "relative rotational mismatch" were also calculated. All tibial inserts were forensically analyzed using the Hood score. Statistical analysis was performed to investigate correlations between TKA component orientation and surface damage (p < 0.05).ResultsFemoral components were found to have axial rotations mainly within ± 3° (68%), whilst 45% of the tibial components and 66% of the relative rotational mismatches were > 3° and < − 3°, respectively. The majority of femoral and tibial components (87% in both cases), as well as the femorotibial angle (70%), showed coronal orientations within ± 3°. The 64% of the tibial components showed posterior tibial slopes out of both the 0°–3° and 5°–7° ranges. There was a significant correlation between tibial slope and damage score on polyethylene tibial inserts (r = 0.2856; p = 0.0382) as well as a significant correlation between implants’ position in the axial plane and damage score on polyethylene tibial inserts (r = 0.6537, p = 0.0240).ConclusionsThis is the first study to use accurate measurements from pre-revision 3DCT to compare tibial and femoral orientation in all three planes with retrieval findings in total knee replacements. A significant correlation between implant position and polyethylene surface damage was found. These results showed the importance of optimizing component position to minimize polyethylene damage. Further analysis involving more accurate polyethylene wear measurements are fundamental to fully understand the role of components’ orientation in TKAs.

Association of facet tropism and orientation with lumbar disc herniation in young patients

Facet tropism and orientation are thought to be associated with lumbar disc herniation (LDH), but the relationship is not well established. Moreover, the effect of facet joint on LDH has not been outlined in young patients. The objective of this study was to investigate the associations of facet joint tropism and orientation with LDH in young patients (18–35 years) by computed tomography (CT). Fifty-three patients with LDH and 129 with neither LDH nor low back pain (18–35 years) were included in this study. The facet joint angles were measured for each facet joint by CT as per the method described by Noren et al. We defined facet tropism as a bilateral angle difference > 5°. Young cases with neither LDH nor low back pain were used as the control group. The results showed that LDH was significantly associated with more coronal facet joint orientation at L1–2 (p = 0.009), L2–3 (p = 0.004), and L3–4 (p = 0.004). No association was established between facet tropism and LDH. This study revealed that facet joint orientation was associated with LDH in young patients (18–35 years); they were more of coronal facing at upper levels. Also, the facet tropism was not associated with LDH.

The Effects of Orientation of Lumbar Facet Joints on the Facet Joint Contact Forces: An In Vitro Biomechanical Study.

A biomechanical human cadaveric study. The aim of this study was to measure L2-L3 facet joint contact forces in a flexibility test using thin film electroresistive sensors, and facet joint orientation on computed tomographic (CT) scan images, to examine the effects of orientation of lumbar facet joint on the facet joint contact forces. Biomechanically, the bilateral facet joints play a critical role in maintaining stability of the lumbar spine. The effect of orientation of lumbar facet joints on the contact forces remains unknown. Eight human cadaveric lumbar spine specimens (L2-L3) were tested by applying a pure moment of ±7.5 Nm in three directions of loading (flexion-extension, lateral bending, and axial rotation) with and without a follower preload of 300 N. The orientation of the lumbar facet joints at the L2-L3 was measured on axial CT scans. Bilateral facet contact forces were measured during flexibility tests using thin film electroresistive sensors (Tekscan 6900). The average total peak facet loads was 66 N in axial rotation, 27 N in extension, and 20 N in lateral bending under a pure moment. Under a pure moment with a follower preload of 300 N, the average total peak facet loads was 53 N in axial rotation, 43 N in extension, and 24 N in lateral bending. The facet joint forces were correlated positively and significantly with the orientation in all directions with and without a compressive follower preload (P < 0.05). In addition, the facet joint contact forces at neutral position with a follower preload were correlated positively with the orientation (rs = 0.759, P = 0.001). This study identified that the greater coronal orientation of lumbar facet joints is, the higher the facet joint contact forces are. 3.

Quantitative Contour Analysis as an Image-based Discriminator Between Benign and Malignant Renal Tumors

To investigate whether morphologic analysis can differentiate between benign and malignant renal tumors on clinically acquired imaging. Between 2009 and 2014, 3-dimensional tumor volumes were manually segmented from contrast-enhanced computerized tomography (CT) images from 150 patients with predominantly solid, nonmacroscopic fat-containing renal tumors: 100 renal cell carcinomas and 50 benign lesions (eg, oncocytoma and lipid-poor angiomyolipoma). Tessellated 3-dimensional tumor models were created from segmented voxels using MATLAB code. Eleven shape descriptors were calculated: sphericity, compactness, mean radial distance, standard deviation of the radial distance, radial distance area ratio, zero crossing, entropy, Feret ratio, convex hull area and convex hull perimeter ratios, and elliptic compactness. Morphometric parameters were compared using the Wilcoxon rank-sum test to investigate whether malignant renal masses demonstrate more morphologic irregularity than benign ones. Only CHP in sagittal orientation (median 0.96 vs 0.97) and EC in coronal orientation (median 0.92 vs 0.93) differed significantly between malignant and benign masses (P = .04). When comparing these 2 metrics between coronal and sagittal orientations, similar but nonsignificant trends emerged (P = .07). Other metrics tested were not significantly different in any imaging plane. Computerized image analysis is feasible using shape descriptors that otherwise cannot be visually assessed and used without quantification. Shape analysis via the transverse orientation may be reasonable, but encompassing all 3 planar dimensions to characterize tumor contour can achieve a more comprehensive evaluation. Two shape metrics (CHP and EC) may help distinguish benign from malignant renal tumors, an often challenging goal to achieve on imaging and biopsy.

Facet Tropism – An Anatomic and CT Scan Study

Facet joint tropism is defined as asymmetry in the facet joint angles, where one joint has a more coronal orientation than the other. Facet joint tropism is currently a subject of intense interest because it has the potential to markedly alter the motion patterns of the lumbar spine and ultimately contribute to low back pain. Objective: The aim of the study was to find out the frequency of facet tropism in the adult lumbar spine. Methods: Lumbar spines from 20 cadavers of adults (18 males and 2 females) aged between 20 and 45 years were dissected. The angle of facet orientation was measured at every level using the technique of Cyron and Hutton. Similarly, available CT scans of thirty six adults between the ages of 20 and 45 years (mean 30 years) were subjected to evaluation of the lumbar spine. The facet angles were measured using digitiser and AutoCAD software. Results: This study showed that the facet tropism occurs frequently in the lumbar spine in general population especially at L4-L5, L5-S1 and L2-L3 levels. There was also a relatively high incidence of facet asymmetry at L2-L3 level in both the cadaveric and the CT Scan study. Conclusion: Facet asymmetry is common at L4-L5, L5-S1 and L2-L3 levels. Advances in Knowledge: Since the lower two lumbar levels are the most mobile segments of the lumbar spine, it is possible that any abnormal geometry of the facet joints could play a part in the pathogenesis of lumbar spinal instability and disc degeneration at these levels.

Anatomical and technical factors associated with superior facet joint violation in lumbar fusion.

OBJECTIVE The aim of this study was to evaluate the anatomical and surgical risk factors for screw-related facet joint violation at the superior level in lumbar fusion. METHODS The authors conducted a retrospective review of a consecutive series of posterior lumbar instrumented fusions performed by a single surgeon. Inclusion criteria were primary lumbar fusion of 1 or 2 levels for degenerative disorders. The following variables were analyzed as possible risk factors: surgical technique (percutaneous vs open screw placement), depth of surgical field, degree of anterior slippage of the superior level, pedicle and facet angle, and facet degeneration of the superior level. Postoperative CT scans were evaluated by 2 independent reviewers. Axial, sagittal, and coronal views were reviewed. Pedicle screws were graded as intra-articular if they clearly interposed between the superior and inferior facet joints of the superior level. Multivariate logistic regression analyses were conducted to assess the factors associated with this complication. RESULTS One hundred thirty-one patients were included. Interobserver reliability for facet joint violation assessment was high (κ = 0.789). The incidence of superior facet joint violation was 12.59% per top-level screw (33 of 262 proximal screws). The rate of facet violation was 28.0% in the percutaneous technique group (14 of 50 patients) and 12.3% in the open surgery group (10 of 81 patients) (OR 2.26, 95% CI 1.09-4.21; p = 0.024). In multivariate logistic regression analysis, independent predictors of facet violation were percutaneous screw placement (adjusted OR 3.31, 95% CI 1.42-7.73; p = 0.006), right-side pedicle screw (adjusted OR 3.14, 95% CI 1.29-7.63; p = 0.011), and facet angle > 45° (adjusted OR 10.95, 95% CI 4.64-25.84; p < 0.0001). CONCLUSIONS The incidence of facet joint violation was higher in percutaneous minimally invasive than in open technique for posterior lumbar spine surgery. Also, coronal orientation of the facet joint is a significant risk factor independent of the surgical technique.

Using the Coronal Evolution to Successfully Forward Model CMEs' In Situ Magnetic Profiles

AbstractPredicting the effects of a coronal mass ejection (CME) impact requires knowing if impact will occur, which part of the CME impacts, and its magnetic properties. We explore the relation between CME deflections and rotations, which change the position and orientation of a CME, and the resulting magnetic profiles at 1 AU. For 45 STEREO‐era, Earth‐impacting CMEs, we determine the solar source of each CME, reconstruct its coronal position and orientation, and perform a ForeCAT (Forecasting a CME's Altered Trajectory) simulation of the coronal deflection and rotation. From the reconstructed and modeled CME deflections and rotations, we determine the solar cycle variation and correlations with CME properties. We assume no evolution between the outer corona and 1 AU and use the ForeCAT results to drive the ForeCAT In situ Data Observer (FIDO) in situ magnetic field model, allowing for comparisons with ACE and Wind observations. We do not attempt to reproduce the arrival time. On average FIDO reproduces the in situ magnetic field for each vector component with an error equivalent to 35% of the average total magnetic field strength when the total modeled magnetic field is scaled to match the average observed value. Random walk best fits distinguish between ForeCAT's ability to determine FIDO's input parameters and the limitations of the simple flux rope model. These best fits reduce the average error to 30%. The FIDO results are sensitive to changes of order a degree in the CME latitude, longitude, and tilt, suggesting that accurate space weather predictions require accurate measurements of a CME's position and orientation.

Can Preoperative CT Scans Be Used to Predict Facial Nerve Stimulation Following CI?

1) To determine the ability of preoperative computed tomography (CT) to predict facial nerve stimulation (FNS) after cochlear implantation (CI). 2) To recognize the limitations of CT in predicting FNS. Patient control study. Tertiary care academic medical center. Adult patients with CI from 2003 to 2015. Patients with severe FNS (n = 4) were compared with randomly selected CI patients (n = 28). Three blinded reviewers evaluated preoperative temporal bone CT scans to measure the distance from the labyrinthine segment of the facial nerve to the basal turn of the cochlea and attempted to predict whether or not the subject had FNS after CI. In total, 32 CT scans were evaluated representing 49 ears that underwent CI.The distances (mm) measured from the labyrinthine segment of the facial nerve to the basal turn of the cochlea in both the axial (0.3 ± 0.3 versus 0.6 ± 0.3) and coronal (0.4 ± 0.2 versus 0.6 ± 0.2) orientation were significantly different between the two groups (p = 0.0001 and p = 0.0034) respectively. The intraclass correlation coefficient demonstrated good (K > 0.7) reviewer correlation in both the reviewers' measurements and predictions. The sensitivity, specificity, positive predictive value, and negative predictive value for preoperative CT scans to predict FNS were 38.5, 85.1, 19.2, and 93.8% respectively. The reviewers were 23% accurate in predicting FNS. Based on a blinded retrospective patient-control study, CT scan measurements show a significantly reduced distance between the labyrinthine facial nerve and the basal turn of the cochlea in patients with FNS. However, it is difficult to predict who will have FNS based on these measurements.

Strain distribution in the porcine lumbar laminae under asymmetric loading.

If the articular facets of the vertebra grow in an asymmetric manner, the developed geometry causes an asymmetry of loading. When the loading environment is altered by way of increased activity, the likelihood of acquiring a stress fracture may be increased. The combination of geometric asymmetry and increased activity is hypothesised to be the precursor to the stress fracture under investigation in this study, spondylolysis. This vertebral defect is an acquired fracture with 7% prevalence in the paediatric population. This value increases to 21% among athletes who participate in hyperextension sports. Tests were carried out on porcine lumbar vertebrae, on which the effect of facet angle asymmetry was simulated by offsetting the load laterally by 7 mm from the mid-point. The aim of the study is to investigate whether an increase in the coronal orientation of one facet leads to an increase in strain in the corresponding vertebral lamina. Strain in the laminae was recorded using six 3-element stacked rosette strain gauges placed bilaterally. Results show that a significant linear predictive relationship exists between load offset and average strain level in the vertebral laminae with p values of 0.006 and 0.045 for principal strains ε1 and ε2 on the right-hand side, and p-values of 0.009 and 0.001 for principal strains ε1 and ε2 on the left-hand side ( R2 all >0.9). This study concludes that facet angle asymmetry does lead to a difference in strain in the vertebral laminae. Change in principal strain as a result of facet asymmetry has a linear relationship and an asymmetry threshold exists beyond which compressive strain on the more coronally oriented facet can be increased by up to 15%.

Multiecho pseudo-golden angle stack of stars thermometry with high spatial and temporal resolution using k-space weighted image contrast.

Implement and evaluate a 3D MRI method to measure temperature changes with high spatial and temporal resolution and large field of view. A multiecho pseudo-golden angle stack-of-stars (SOS) sequence with k-space weighted image contrast (KWIC) reconstruction was implemented to simultaneously measure multiple quantities, including temperature, initial signal magnitude M(0), transverse relaxation time ( T2*), and water/fat images. Respiration artifacts were corrected using self-navigation. KWIC artifacts were removed using a multi-baseline library. The phases of the multiple echo images were combined to improve proton resonance frequency precision. Temperature precision was tested through in vivo breast imaging (N = 5 healthy volunteers) using both coronal and sagittal orientations and with focused ultrasound (FUS) heating in a pork phantom using a breast specific MR-guided FUS system. Temperature measurement precision was significantly improved after echo combination when compared with the no echo combination case (spatial average of the standard deviation through time of 0.3-1.0 and 0.7-1.9°C, respectively). Temperature measurement accuracy during heating was comparable to a 3D seg-EPI sequence. M(0) and T2* values showed temperature dependence during heating in pork adipose tissue. A self-navigated 3D multiecho SOS sequence with dynamic KWIC reconstruction is a promising thermometry method that provides multiple temperature sensitive quantitative values. Magn Reson Med 79:1407-1419, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Averaging rotational landmarks during total knee arthroplasty reduces component malrotation caused by femoral asymmetry

BackgroundFemoral component malrotation is a common cause of patient dissatisfaction after total knee arthroplasty. The sulcus line (SL) is more accurate than Whiteside’s line as it corrects for variation in the coronal orientation of the groove. The hypothesis is that averaging the SL and posterior condylar axis (PCA) will reduce femoral malrotation.MethodsThe component was inserted at a position between the SL and PCA in 91 patients. An intraoperative photograph was taken showing the landmarks. These were compared to the component position achieved relative to the surgical epicondylar axis (SEA) on a postoperative CT scan. The component position was compared to the position achieved using the individual landmarks.ResultsRelative to the SEA, the final component position was 0.6° (SD 1.4°, range −3.8° to +4.0°), the coronally corrected SL position was −0.7° (SD 2.3°, −5.5° to +4.6°), the PCA position was 0.9° (SD 1.9°, −6.1° to +5.0°). Averaging the landmarks significantly decreased the variance of the component position compared to using the SL and PCA individually. The number of outliers (>3° from SEA) was also significantly less (p < 0.05) for the average position (2/84) when each was compared to the SL (16/84) and PCA (14/84) individually. In 21/84 (25%) of cases, there was more than 4° of divergence between the SL and PCA.ConclusionsAveraging the SL and the PCA decreases femoral component malrotation. Femora are frequently asymmetrical in the axial plane. Referencing posterior condyles alone to set rotation is likely to cause high rates of patellofemoral malalignment.

An in vitro evaluation of the maxillary occlusal plane orientation obtained with an electronic application: A preliminary investigation

Statement of problemIn the evaluation and fabrication of dental prostheses, maxillary occlusal plane orientation in the sagittal and coronal planes may affect functional and esthetic outcomes. The accuracy of a recently developed electronic application in transferring this orientation to a semiadjustable articulator has not been evaluated. PurposeThe purpose of this in vitro study was to evaluate the coronal and sagittal orientation of the occlusal plane on maxillary casts mounted with an electronic application facebow system onto a corresponding semiadjustable arcon articulator. Material and methodsA maxillary typodont was placed into a phantom head (control) oriented with the Frankfort horizontal plane parallel to the horizon. A digital protractor was used to measure the angle between the occlusal plane of the maxillary arch of the phantom head and the Frankfort horizontal plane along the sagittal and coronal planes. The commercial system (test group) was used to make 15 facebow records of the maxillary typodont within the phantom head. The system records were used to mount diagnostic casts of the maxillary typodont onto a semiadjustable arcon articulator. The same measurements were made on the mounted diagnostic casts and were compared with the control. Statistical differences between the occlusal plane of the control and the occlusal plane of the mounted maxillary casts were determined using the 1-sample t test (α=.05). ResultsThe coronal orientation of the occlusal plane was significantly different (P<.001) between test group and control. No significant differences (P>.05) were found in the sagittal orientation of the occlusal plane. ConclusionsWithin the limitations of this study, variations in the coronal plane orientation were observed with the system. Variations in this plane may lead to adverse evaluation and clinical outcomes.

Value of the cumulative sum test for the assessment of a learning curve: Application to the introduction of patient-specific instrumentation for total knee arthroplasty in an academic department

BackgroundThe purpose of the study was to use the cumulative summation (CUSUM) test to assess the learning curve during the introduction of a new surgical technique (patient-specific instrumentation) in total knee arthroplasty (TKA) in an academic department. MethodsThe first 50TKAs operated on at an academic department using patient-specific templates (PSTs) were scheduled to enter the study. All patients had a preoperative computed tomography scan evaluation to plan bone resections. The PSTs were positioned intraoperatively according to the best-fit technique and their three-dimensional orientation was recorded by a navigation system. The position of the femur and tibia PST was compared to the planned position for four items for each component: coronal and sagittal orientation, medial and lateral height of resection. Items were summarized to obtain knee, femur and tibia PST scores, respectively. These scores were plotted according to chronological order and included in a CUSUM analysis. The tested hypothesis was that the PST process for TKA was immediately under control after its introduction. ResultsCUSUM test showed that positioning of the PST significantly differed from the target throughout the study. There was a significant difference between all scores and the maximal score. No case obtained the maximal score of eight points. The study was interrupted after 20 cases because of this negative evaluation. ConclusionThe CUSUM test is effective in monitoring the learning curve when introducing a new surgical procedure. Introducing PST for TKA in an academic department may be associated with a long-lasting learning curve.The study was registered on the clinical.gov website (Identifier NCT02429245).

Evaluation of Transplanted Kidneys and Comparison with Healthy Volunteers and Kidney Donors with Diffusion-Weighted Magnetic Resonance Imaging: Initial Experience.

The aim of this study was to evaluate the feasibility of diffusion-weighted magnetic resonance, by comparing imaging in renal allograft recipients for functional assessment of kidney transplants versus imaging of these features in healthy volunteers and kidney donors with native kidneys. Seventy renal transplant recipients (group A) with stable graft function at postoperative month 1, 40 healthy volunteers (group B), and 40 kidney donors (group C) underwent diffusion-weighted magnetic resonance imaging. An echo-planar diffusion-weighted imaging sequence was performed in coronal orientation by using 6 b values (0, 200, 400, 600, 800, 1000 s/mm²). The apparent diffusion coefficients were determined for the upper and lower poles of the kidney cortex and medulla. Relations between apparent diffusion coefficients and allograft function, determined by the estimated glomerular filtration rate (comparing rates > 60 mL/min/1.73 m² [group A1] versus < 60 mL/min/1.73 m² [group A2]), were investigated in renal transplant recipients, and apparent diffusion coefficients in groups A, B, and C were compared. Apparent diffusion coefficients were statistically higher in group A1 than in group A2 (P < .05) and statistically higher in group A than in groups B and C (P < .001). There were no significant differences between groups B and C (P > .05). We observed that apparent diffusion coefficients of transplanted kidneys at postoperative month 1 were higher than values in native kidneys of healthy volunteers and kidney donors. In addition, apparent diffusion coefficients of transplanted kidneys with estimated glomerular filtration rates > 60 mL/min/1.73 m² were higher than transplanted kidneys with rates < 60 mL/min/1.73 m².

Patient-specific instrumentation for total knee arthroplasty.

To assess the accuracy of total knee replacements (TKRs) performed using CT-based patient-specific instrumentation by postoperative CT scan. Approval from the Ethics Committee was granted prior to commencement of this study. Fifty prospective and consecutive patients who had undergone TKR (Evolis, Medacta International) using CT-based patient-specific instrumentation (MY KNEE, Medacta International) were assessed postoperatively using a CT scan and the validated Perth protocol measurement technique. The hip-knee-ankle (HKA) angle of the lower limb in the coronal plane; the coronal, sagittal, and rotational orientation of the femoral component; and the coronal and sagittal orientation of the tibial component were measured. These results were then compared to each patient's preoperative planning. The percentage of patients found to be less than or equal to 3° of planned alignment was calculated. One patient was excluded as the femoral cutting block did not fit the femur as predicted by planning and therefore underwent a conventional TKR. Ninety-eight percent of patients were within 3° of planned alignment in the coronal plane reproducing the predicted HKA angle. Predicted coronal plane orientation of the tibial and femoral component was achieved in 100% and 96% of patients, respectively. The sagittal orientation of the femoral component was within 3° in 98% of patients. The planned sagittal positioning of the tibial component was achieved in 92% of patients. Furthermore, 90% of patients were found to have a femoral rotation within 3° of planning. Eighty-six percent of patients achieved good-to-excellent outcome at 12 months (Oxford Knee Score > 34). We have found that TKR using this patient-specific instrumentation accurately reproduces preoperative planning in all six of the parameters measured in this study.

Heads you win, tails you lose: filtration processing for the microscopical examination of sperm heads.

The sperm head plays a key role in many fertilisation events and determining the precise location of molecules within the head region is important in mechanistically dissecting the fertilisation process. Such molecules may be present in low copy number and many sperm head profiles must be examined to localise them to particular subcellular structures with confidence. Filtration has traditionally been used for the purpose of concentrating biological material, such as free-living cells, spores, and subcellular fractions, and little attempt has been made to extend the procedure to encompass the entire processing schedule, mainly due to the incompatibility of intermediate dehydrating solvents with membrane filters. The novel and simple technique of filtration processing that we describe produced a dense mat of cells, with several sperm heads being visible in coronal orientation in a high-power field at the light microscopic level, and allowed positive immunocytochemical staining to be identified with confidence. This new technique exploits the low viscosity of LR White acrylic resin to allow the entire processing procedure to be undertaken in the filtration apparatus. In contrast, conventional techniques for preparing free-living cells, namely pre-embedding in a supportive matrix prior to processing, and centrifugation at each stage of the processing procedure, proved suboptimal, partly due to the final concentration that could be achieved, but mainly due to the random orientation of cells that these techniques afforded.

A DATA-DRIVEN ANALYTIC MODEL FOR PROTON ACCELERATION BY LARGE-SCALE SOLAR CORONAL SHOCKS

ABSTRACT We have recently studied the development of an eruptive filament-driven, large-scale off-limb coronal bright front (OCBF) in the low solar corona, using remote observations from the Solar Dynamics Observatory’s Advanced Imaging Assembly EUV telescopes. In that study, we obtained high-temporal resolution estimates of the OCBF parameters regulating the efficiency of charged particle acceleration within the theoretical framework of diffusive shock acceleration (DSA). These parameters include the time-dependent front size, speed, and strength, as well as the upstream coronal magnetic field orientations with respect to the front’s surface normal direction. Here we present an analytical particle acceleration model, specifically developed to incorporate the coronal shock/compressive front properties described above, derived from remote observations. We verify the model’s performance through a grid of idealized case runs using input parameters typical for large-scale coronal shocks, and demonstrate that the results approach the expected DSA steady-state behavior. We then apply the model to the event of 2011 May 11 using the OCBF time-dependent parameters derived by Kozarev et al. We find that the compressive front likely produced energetic particles as low as 1.3 solar radii in the corona. Comparing the modeled and observed fluences near Earth, we also find that the bulk of the acceleration during this event must have occurred above 1.5 solar radii. With this study we have taken a first step in using direct observations of shocks and compressions in the innermost corona to predict the onsets and intensities of solar energetic particle events.

Increased Pelvic Incidence is Associated With a More Coronal Facet Orientation in the Lower Lumbar Spine: A Cadaveric Study of 599 Lumbar Spines.

An anatomic study of facet angle orientation and morphology of the lumbar spine was performed. The aim of this study was to determine how age, gender, race, and pelvic incidence (PI) correlate with facet orientation in the lumbar spine. Lumbar facet orientation has important implications in the development of numerous pathologies of the spine, including arthritis, spondylolisthesis, and adult spinal deformity. Preliminary reports have suggested that sagittal balance of the spine may contribute to facet joint orientation. We therefore designed an anatomic study to investigate the relationship between PI and facet orientation, within the context of age, gender, and race. Five hundred ninety-nine cadaveric lumbar spines were obtained from the Hamann-Todd osteological collection. It was determined that facet angle was most reliably assessed by measuring the angle between the superior articular facet and the spinous process. Facet angles were measured bilaterally at each level from T12-L1 through L5-S1 in every specimen. Multivariate regression analysis was used to determine independent predictors of facet angle at each level. Facet angle increased rostrally to caudally, from 22.6 ± 8.3° at T12-L1 to 49.1 ± 12.4° at L5-S1. Cadaver age was an independent predictor of a more sagittal facet angle at lower spinal levels. Caucasian race was an independent predictor of increasing facet angle. Increased PI had no effect on facet angle at T12-L1, L1-L2, L2-L3, or L3-L4, although was a significant predictor of more coronally oriented facet joints at L4-L5 (standardized beta 0.096, P = 0.009) and L5-S1 (standardized beta 0.079, P = 0.032). The results of this study provide important data regarding differences in facet angle that exists between individuals. Moreover, the results of this study suggest that facet joints do possess the ability to remodel over time, perhaps in response to perturbations of sagittal balance, osteophyte formation, or other yet to be determined factors. N/A.

Ilizarov tibial lengthening in the skeletally immature patient.

We wished to examine the effectiveness of tibial lengthening using a two ring Ilizarov frame in skeletally immature patients. This is a potentially biomechanically unstable construct which risks the loss of axial control. We retrospectively reviewed a consecutive series of 24 boys and 26 girls, with a mean age of 8.6 years (4 to 14), who underwent 52 tibial lengthening procedures with a mean follow-up of 4.3 years (4.0 to 16.9). Tibial alignment was measured before and after treatment using joint orientation lines from the knee and a calculation of the oblique plane axis. The mean percentage length gain was 20% (13 to 31) with a mean bone-healing index (BHI) of 34 days per centimetre (20 to 54). Age at surgery and location of the osteotomy site showed a strong relationship as the location of the osteotomy migrated more proximally with age. However, no significant correlation was found between BHI and the position of the osteotomy. The coronal and sagittal joint orientation of the lengthened tibias were within the normal range in 67% and 92% of cases, respectively. The oblique plane angulation calculation revealed a statistically significant change pre- to post-operatively in both magnitude (p < 0.05) and direction (p < 0.01), but without clinical consequence. The majority of complications were minor (n = 40 in 27 patients; 1.48 complications per segment lengthened) with no residual disability reported. Two-ring tibial lengthening is effective in maintaining segmental alignment, efficient in callous production and relatively comfortable for the patient with few significant complications. Cite this article: Bone Joint J 2016;98-B:1276-82.

Metal Artifact Reduction MRI of Total Ankle Arthroplasty

Category: Ankle Arthritis Introduction/Purpose: Total ankle arthroplasty (TAA) is an often successful treatment for end-stage ankle arthritis; however, a subset of patient presents with ankle pain following TAA and concern for early failure. Although radiographs are often diagnostic, patients with normal radiographs and continued pain pose a diagnostic challenge. In those patients, magnetic resonance imaging (MRI) may be helpful to evaluate periprosthetic bone and soft tissues. Traditional high-bandwidth (high-BW) metal artifact reduction sequence (MARS) MRI lessens metal artifacts, but image distortions remain with Cobalt-Chromium implants. Slice- Encoding-Metal-Artifact-Correction (SEMAC) is a recently FDA-approved, advanced MARS technique that promises more powerful metal suppression. Therefore, we prospectively tested the hypothesis that SEMAC MARS MRI facilitates better metal reduction and visibility of periprosthetic structures than does traditional MARS MRI in patients with TAA. Methods: In this IRB-approved study, 20 volunteers [10 females/10 males; age, 59 (41-73) years, 15 (3-24) months post- operatively] with TAA were prospectively enrolled. The research protocol consisted of high-BW and SEMAC MARS MRI using a clinical 1.5 Tesla MRI scanner and a dedicated boot-shaped MRI coil. For each technique, intermediate-weighted and fat- suppressed MR images were obtained in axial, sagittal and coronal orientation. Three observes (2 foot/ankle surgeons and 1 musculoskeletal radiologist) evaluated the high-BW and SEMAC MR images in an independent, random and blinded fashion. Equidistance 5-point Likert scales (1=non-diagnostic, 5=very good) were used to grade image quality as well as the quality of metal suppression and visibility of bone-metal interfaces, tendons, ligaments, bone and joints. Differences between the two MARS techniques were assessed with a Kruskall-Wallis test, and interobserver agreement was graded with Intraclass-Correlation- Coefficient (ICC). Bonferroni-corrected p-values ≤ 0.01 were considered significant. Results: All 20 subjects completed the research protocol. There was good agreement between observers (ICC = 0.79; 95% CI, 0.78-0.80). Image quality of high-BW and SEMAC MR images was similar for tissue contrast, fat suppression, and fluid brightness, whereas image sharpness was one interval higher on high-BW images than on SEMAC images (p &lt; 0.01). Metal reduction of TAA components was significantly better (p &lt; 0.01) on SEMAC images (very good) than on high-BW images (poor-to-adequate). At level of the implants, long flexor and peroneal tendons, deep deltoid, syndesmotic and lateral collateral ligaments, and medial and lateral gutters were significantly better seen (p &lt; 0.01) on SEMAC images (good-to-very good) than on high-BW images (poor-to- adequate). Similar visibility (good-to-very good) was found for the remainder of the tendons, ligaments, bones and joints. Conclusion: Based on the results of our study, we accept the hypothesis that SEMAC MARS MRI outperforms traditional high- BW MARS MRI in the degree of metal artifact reduction as well as visibility of bone implant interfaces and periprosthetic tendons and ligaments at level of the joint line. We believe advanced MARS MRI can be a valuable clinical tool to assess osseous integration and soft tissue lesions in patients following TAA.