Background: Anterior cruciate ligament (ACL) injury can lead to changes in tibiofemoral kinematics during gait, but the detailed short-term kinematic changes after ACL injury are still unknown.... Show moreBackground: Anterior cruciate ligament (ACL) injury can lead to changes in tibiofemoral kinematics during gait, but the detailed short-term kinematic changes after ACL injury are still unknown. Purpose: To measure tibiofemoral kinematics during gait in ACL-deficient (ACLD) knees over time after ACL injury. Study Design: Controlled laboratory study. Methods: The authors categorized 76 patients with unilateral ACLD knees into 4 groups based on the time from injury: <3 months (group 1), 3 to 6 months (group 2), >6 to 12 months (group 3), and >12 months (group 4). The controls were 20 participants with ACL-intact knees. Changes in the knee kinematics and range of motion during gait were compared among ACLD groups and those with ACL-intact knees. Results: Compared with controls, the range of motion of flexion in group 1 was significantly lower (6 degrees; P = .033), and the mean knee flexion was significantly increased (0.7 degrees-3.4 degrees) in groups 1 to 4 (all P <= .004). There was more internal tibial rotation (2.9 degrees-4.3 degrees) in group 1 and 2, and more anterior tibial translation (4.3 mm) in group 1 during the stance or swing phases than in controls (P <= .049 for all). The mean internal tibial rotation and anterior tibial translation significantly decreased from group 1 to group 4 (P < .001 for both). Compared with controls, the mean medial tibial translation was significantly greater (1.2-2.5 mm) in all groups, and more medial tibial translations (2.4-3.7 mm) were observed during the stance phase in groups 1, 3, and 4 (P <= .047 for all). Conclusion: ACLD knees displayed a motion impairment walking strategy within 3 months, and a higher-flexion walking strategy increased with time after injury. Excessive anterior translation and internal rotation of the tibia tended to return to normal, while excessive medial translation of the tibia increased in ACLD knees after 6 months postinjury. These results may provide new insight into the compensatory mechanisms and risk factors for premature osteoarthritis in ACLD knees. Show less
A rehabilitation program after anterior cruciate ligament reconstruction is of great importance to obtain a satisfactory prognosis after surgery. However, there is still an onging debate over... Show moreA rehabilitation program after anterior cruciate ligament reconstruction is of great importance to obtain a satisfactory prognosis after surgery. However, there is still an onging debate over whether closed kinetic chain or open kinetic chain exercises should be chosen. Our study was designed to compare the in vivo tibiofemoral kinematics during closed kinetic chain and open kinetic chain exercises. Eighteen healthy volunteers were asked to perform box squat and unloaded/10 kg-loaded seated knee extension. In vivo 3-dimensional analysis of tibiofemoral kinematics of different motions were determined using a dual fluoroscopic imaging system. The study found significantly more tibial anterior displacement during loaded seated knee extension than during unloaded seated knee extension from 25 degrees-50 degrees of knee flexion (p < 0.031). The knees exhibited significantly more internal tibial rotation and lateral tibial translation during the box squat than both seated knee extensions during mid-flexion. In addition, the knees showed less internal-external (IE) range of motion (ROM) from 20 degrees- 75 degrees of flexion (p < 0.001) and medial-lateral (ML) ROM from 75 degrees to full extension (p < 0.006) during box squat than both extensions. This knowledge may help optimize rehabilitation plans for patients post ACL reconstruction. Show less
Segmentation of medical images, particularly late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) used for visualizing diseased atrial structures, is a crucial first step for ablation... Show moreSegmentation of medical images, particularly late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) used for visualizing diseased atrial structures, is a crucial first step for ablation treatment of atrial fibrillation. However, direct segmentation of LGE-MRIs is challenging due to the varying intensities caused by contrast agents. Since most clinical studies have relied on manual, labor-intensive approaches, automatic methods are of high interest, particularly optimized machine learning approaches. To address this, we organized the 2018 Left Atrium Segmentation Challenge using 154 3D LGE-MRIs, currently the world's largest atrial LGE-MRI dataset, and associated labels of the left atrium segmented by three medical experts, ultimately attracting the participation of 27 international teams. In this paper, extensive analysis of the submitted algorithms using technical and biological metrics was performed by undergoing subgroup analysis and conducting hyper-parameter analysis, offering an overall picture of the major design choices of convolutional neural networks (CNNs) and practical considerations for achieving state-of-the-art left atrium segmentation. Results show that the top method achieved a Dice score of 93.2% and a mean surface to surface distance of 0.7 mm, significantly outperforming prior state-of-the-art. Particularly, our analysis demonstrated that double sequentially used CNNs, in which a first CNN is used for automatic region-of-interest localization and a subsequent CNN is used for refined regional segmentation, achieved superior results than traditional methods and machine learning approaches containing single CNNs. This large-scale benchmarking study makes a significant step towards much-improved segmentation methods for atrial LGE-MRIs, and will serve as an important benchmark for evaluating and comparing the future works in the field. Furthermore, the findings from this study can potentially be extended to other imaging datasets and modalities, having an impact on the wider medical imaging community. (C) 2020 Elsevier B.V. All rights reserved. Show less
Unfavorable clinical outcomes after medial patellofemoral ligament (MPFL) reconstruction, such as early osteoarthritis of the patellofemoral joint, were considered to be associate with tunnel... Show moreUnfavorable clinical outcomes after medial patellofemoral ligament (MPFL) reconstruction, such as early osteoarthritis of the patellofemoral joint, were considered to be associate with tunnel malpositioning. Length change studies have found that small changes in the femoral position can cause great changes in elongation trends. Further studying the MPFL kinematics may help us to understand the consequences of tunnel malpositioning and optimize the reconstruction techniques. Fifteen healthy subjects were studied with a combined computed tomography and biplane fluoroscopic imaging technique during a lunge motion. Five femoral and three patellar attachments were used to simulate different MPFL bundles. Kinematics of MPFL was defined as elongation and orientation changes (i.e., deviation angle and elevation angle). The mean deviation angle was 28.7 degrees (95% confidence interval, 28.0 degrees-29.4 degrees) at full extension and remained nearly unchanged up to 60 degrees of flexion, and increased to 56.5 degrees (54.1 degrees-58.9 degrees) at 110 degrees. The elevation angle decreased linearly from 12.6 degrees (9.3 degrees-15.9 degrees) at full extension to -86.2 degrees (-92.7-79.7 degrees) at 110 degrees of flexion. The MPFL was most stretched anteriorly and laterally relative to femur from full extension to 30 degrees of flexion and remained near isometric beyond 30 degrees. The current study found that proximal and anterior femoral attachments caused excessive lateral stretching of the MPFL at deeper flexion angles. Such abnormal MPFL kinematics may subsequently cause overconstraint and increased cartilage pressures of the medial patellofemoral joint. Show less
