scholarly journals In Vivo Kinematics of the Extensor Mechanism of the Knee During Deep Flexion

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Koichi Kobayashi ◽  
Ali Hosseini ◽  
Makoto Sakamoto ◽  
Wei Qi ◽  
Harry E. Rubash ◽  
...  
Keyword(s):  
Patellar Tendon ◽  
Knee Flexion ◽  
Extensor Mechanism ◽  
Deep Flexion ◽  
Contact Points ◽  
Patellar Cartilage ◽  
Joint Contact ◽  
Joint Biomechanics ◽  
Few Data

While various factors have been assumed to affect knee joint biomechanics, few data have been reported on the function of the extensor mechanism in deep flexion of the knee. This study analyzed the patellofemoral joint contact kinematics and the ratio of the quadriceps and patellar tendon forces in living subjects when they performed a single leg lunge up to 150 deg of flexion. The data revealed that in the proximal-distal direction, the patellofemoral articular contact points were in the central one-third of the patellar cartilage. Beyond 90 deg of flexion, the contact points moved towards the medial-lateral edges of the patellar surface. At low flexion angles, the patellar tendon and quadriceps force ratio was approximately 1.0 but reduced to about 0.7 after 60 deg of knee flexion, implying that the patella tendon carries lower loads than the quadriceps. These data may be valuable for improvement of contemporary surgical treatments of diseased knees that are aimed to achieve deep knee flexion.

Effect of Patellar Tendon Shortening on Tracking of the Patella

2005 ◽  
Vol 33 (10) ◽  
pp. 1565-1574 ◽  
Author(s):  
Neil Upadhyay ◽  
Samuel R. Vollans ◽  
Bahaa B. Seedhom ◽  
Roger W. Soames
Keyword(s):  
Patellar Tendon ◽  
Contact Area ◽  
Knee Flexion ◽  
Patellofemoral Joint ◽  
Contact Stresses ◽  
Contact Areas ◽  
Before And After ◽  
Joint Contact ◽  
Joint Biomechanics ◽  
Patellar Tendon Shortening

Background Although 10% postoperative patellar tendon shortening after bone–patellar tendon–bone autograft reconstruction of the anterior cruciate ligament has been reported, there are no published studies assessing the effect of shortening on patellofemoral joint biomechanics under physiological loading conditions. Purpose To investigate the influence of patellar tendon shortening on patellofemoral joint biomechanics. Study Design Controlled laboratory study. Methods The authors evaluated the patellofemoral contact area, the location of contact, and the patellofemoral joint reaction force and contact stresses in 7 cadaveric knees before and after 10% patellar tendon shortening. Shortening was achieved using a specially designed device. Experimental conditions simulating those occurring during level walking were employed: physiological quadriceps loads and corresponding angles of tibial rotation were applied at 15 °, 30 °, and 60 ° flexion of the knee. Patellofemoral joint contact areas were measured before and after shortening using the silicone oil–carbon black powder suspension squeeze technique. Results After patellar tendon shortening, patellofemoral joint contact areas were displaced proximally on the patellar surface and distally on the femoral surface. Although the contact area increased by 18% at 15 ° of knee flexion (P=. 04), no significant change occurred at 30 ° or 60 ° of knee flexion (P>. 05). Patellofemoral contact stress remained unchanged after patellar tendon shortening (P>. 05) at each flexion angle. Conclusion Our results suggest that a 10% shortening of the patellar tendon does not alter patellar contact stresses during locomotion. It is not clear whether apparent changes in contact location in all positions and contact area at 15 ° would have clinical consequences.

scholarly journals Validation of an MRI-based method to assess patellofemoral joint contact areas in loaded knee flexion in vivo

2013 ◽  
Vol 39 (4) ◽  
pp. 978-987 ◽  
Author(s):  
Emily J. McWalter ◽  
Colm M. O'Kane ◽  
David P. FitzPatrick ◽  
David R. Wilson
Keyword(s):  
Knee Flexion ◽  
Patellofemoral Joint ◽  
Contact Areas ◽  
Joint Contact

scholarly journals In-vivo patellar tendon kinematics during weight-bearing deep knee flexion

2012 ◽  
Vol 30 (10) ◽  
pp. 1596-1603 ◽  
Author(s):  
Koichi Kobayashi ◽  
Makoto Sakamoto ◽  
Ali Hosseini ◽  
Harry E. Rubash ◽  
Guoan Li
Keyword(s):  
Patellar Tendon ◽  
Knee Flexion ◽  
Weight Bearing

Influence of the Level of Muscular Redundancy on the Validity of a Musculoskeletal Model

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Florent Moissenet ◽  
Laurence Chèze ◽  
Raphaël Dumas
Keyword(s):  
Gait Pattern ◽  
Musculoskeletal Model ◽  
Contact Forces ◽  
Generic Model ◽  
Grand Challenge ◽  
Contact Points ◽  
Lateral Contact ◽  
Musculoskeletal Models ◽  
Joint Contact

While recent literature has clearly demonstrated that an extensive personalization of the musculoskeletal models was necessary to reach high accuracy, several components of the generic models may be further investigated before defining subject-specific parameters. Among others, the choice in muscular geometry and thus the level of muscular redundancy in the model may have a noticeable influence on the predicted musculotendon and joint contact forces. In this context, the aim of this study was to investigate if the level of muscular redundancy can contribute or not to reduce inaccuracies in tibiofemoral contact forces predictions. For that, the dataset disseminated through the Sixth Grand Challenge Competition to Predict In Vivo Knee Loads was applied to a versatile 3D lower limb musculoskeletal model in which two muscular geometries (i.e., two different levels of muscular redundancy) were implemented. This dataset provides tibiofemoral implant measurements for both medial and lateral compartments and thus allows evaluation of the validity of the model predictions. The results suggest that an increase of the level of muscular redundancy corresponds to a better accuracy of total tibiofemoral contact force whatever the gait pattern investigated. However, the medial and lateral contact forces ratio and accuracy were not necessarily improved when increasing the level of muscular redundancy and may thus be attributed to other parameters such as the location of contact points. To conclude, the muscular geometry, among other components of the generic model, has a noticeable impact on joint contact forces predictions and may thus be correctly chosen even before trying to personalize the model.

Knee Kinematics During an In Vitro Simulated Deep Flexion Squat

2007 ◽  
Author(s):  
Chadd W. Clary ◽  
Amit M. Mane ◽  
Amber N. Reeve ◽  
Kevin A. Dodd ◽  
Lorin P. Maletsky
Keyword(s):  
Knee Flexion ◽  
Weight Bearing ◽  
Knee Kinematics ◽  
Knee Prostheses ◽  
Deep Flexion ◽  
Total Knee ◽  
Design Characteristics ◽  
Insight Into

Understanding the behavior of the natural knee in deep flexion can offer insight into the necessary design characteristics of a total knee implant. Andriacchi et al. [1] measured the in vivo characteristics of knee motion down to ∼150° knee flexion during a weight bearing squat. Likewise, Li et al. [2] investigated deep knee flexion in vitro using robotic technology during passive knee flexion. Both of these studies offer insight into the behavior of the knee in deep knee flexion; however, they have some limitations with regards to assessing physiological activities in a controlled manner. The purpose of this study was to measure the kinematics of the knee during a simulated in vitro deep knee squat so that in the future a dynamic, load-bearing, simulated deep knee squat could be used as a tool in the design of total knee prostheses.

A PHOTOELASTIC MODEL OF THE PATELLOFEMORAL JOINT TO STUDY PATELLAR HEIGHT

2020 ◽  
Vol 20 (07) ◽  
pp. 2050049
Author(s):  
GUSTAVO APARICIO
Keyword(s):  
Knee Flexion ◽  
Patellofemoral Joint ◽  
Contact Point ◽  
Reaction Force ◽  
Patellar Height ◽  
Extensor Mechanism ◽  
Moment Arm ◽  
Moment Arms ◽  
Contact Points ◽  
Ligamentum Patellae

Background: Patellar height has been related to anterior knee pain and Osgood–Schlatter disease. To study the influence of patellar height on knee biomechanics, a bidimensional photoelastic prototype of the patellofemoral joint was developed. Methods: Nine tests were performed at different knee flexion angles and patellar heights. A free body diagram was constructed for each test. The following parameters were calculated: lengths (patella, patella thickness and ligamentum patellae); patellar height index; angles (knee flexion, patellar flexion, quadriceps and ligamentum patellae force and reaction force at the ankle); moment arms (extensor, quadriceps and ligamentum patellae in relation to both the tibiofemoral and patellofemoral contact points), effective moment arm and forces around the extensor mechanism relative to the applied force. Results: Femoropatellar and femorotibial reaction forces were greater with increased knee flexion and a fixed patellar height. With fixed knee flexion and different patellar heights, these forces were greater if the patella was elevated. A decrease in the angle between the tibial axis and ligamentum patellae was observed when patellar height increased. Patellar flexion angle increased when patellar height increased. This was accompanied by an increase in the angle of action of the quadriceps force. Extensor moment arm decreased with increased patellar height when knee flexion and the tibiofemoral contact point were fixed. Conclusion: A new application of photoelasticity is presented. The preliminary findings obtained confirm the influence of patellar height on patellar biomechanics, and specifically on forces around the extensor mechanism of the knee.

PATELLA TRACKING WITH PERIPATELLAR SOFT TISSUE STABILIZERS AS A FUNCTION OF DYNAMIC SUBJECT-SPECIFIC KNEE FLEXION

2011 ◽  
Vol 11 (05) ◽  
pp. 1025-1043 ◽  
Author(s):  
J. H. MÜLLER ◽  
C. SCHEFFER ◽  
A. ELVIN ◽  
P. J. ERASMUS ◽  
E. M. DILLON
Keyword(s):  
Knee Flexion ◽  
Load Ratio ◽  
Quadriceps Tendon ◽  
Musculoskeletal Modeling ◽  
Musculoskeletal Models ◽  
Subject Specific ◽  
Joint Biomechanics ◽  
Load Component ◽  
Patella Tracking

Musculoskeletal modeling has found wide application in joint biomechanics investigations. This technique has been improved by incorporating subject-specific skeletal elements and passive patellofemoral stabilizers in a dynamic analysis. After trochlear engagement, the volunteers' patellae displaced laterally, whereas tilt was subject specific. Comparison of the tilt and mediolateral position values to in vivo MRI values at 30° knee flexion showed a mean accuracy of 84.4% and 96.9%, respectively. Medial patellofemoral ligament tension decreased with knee flexion, while the patellar tendon–quadriceps tendon ratio ranged from 0.4 to 1.2. The patellofemoral contact load–quadriceps tendon load ratio ranged from 0.7 to 1.3, whereas the mediolateral load component–resultant load ratio ranged from 0 to 0.4. Three validated subject-specific musculoskeletal models facilitated the analysis of patellofemoral biomechanics: Subject-specific patella tracking and passive stabilizer response was analyzed as a function of dynamic knee flexion.

The Pattern of Ventricular Remodeling Influences the Level of Oxidative Stress in Heart Failure Patients

2017 ◽  
Vol 68 (7) ◽  
pp. 1506-1511
Author(s):  
Cerasela Mihaela Goidescu ◽  
Anca Daniela Farcas ◽  
Florin Petru Anton ◽  
Luminita Animarie Vida Simiti
Keyword(s):  
Oxidative Stress ◽  
Heart Failure ◽  
Ventricular Remodeling ◽  
Clinical Laboratory ◽  
Left Ventricular ◽  
Control Group ◽  
Reactive Protein ◽  
Lv Mass ◽  
Few Data

Oxidative stress (OS) is increased in chronic diseases, including cardiovascular (CV), but there are few data on its effects on the heart and vessels. The isoprostanes (IsoP) are bioactive compounds, with 8-iso-PGF25a being the most representative in vivo marker of OS. They correlate with the severity of heart failure (HF), but because data regarding OS levels in different types of HF are scarce, our study was aimed to evaluate it by assessing the urinary levels of 8-iso-PGF2aand its correlations with various biomarkers and parameters. Our prospective study included 53 consecutive patients with HF secondary to ischemic heart disease or dilative cardiomyopathy, divided according to the type of HF (acute, chronic decompensated or chronic compensated HF). The control group included 13 hypertensive patients, effectively treated. They underwent clinical, laboratory - serum NT-proBNP, creatinine, uric acid, lipids, C reactive protein (CRP) and urinary 8-iso-PGF2a and echocardiographic assessment. HF patients, regardless the type of HF, had higher 8-iso-PGF2a than controls (267.32pg/�mol vs. 19.82pg/�mol, p[0.001). The IsoP level was directly correlated with ejection fraction (EF) (r=-0.31, p=0.01) and NT-proBNP level (r=0.29, p=0.019). The relative wall thickness (RWT) was negatively correlated with IsoP (r=-0.55, p[0.001). Also 8-iso-PGF25a was higher by 213.59pg/�mol in the eccentric left ventricular (LV) hypertrophy subgroup comparing with the concentric subgroup (p=0.014), and the subgroups with severe mitral regurgitation (MR) and moderate/severe pulmonary hypertension (PAH) had the highest 8-iso-PGF2a levels. Male sex, severe MR, moderate/severe PAH, high LV mass and low RWT values were predictive for high OS level in HF patients.Eccentric cardiac remodeling, MR severity and PAH severity are independent predictors of OS in HF patients.

scholarly journals Quantitative analysis on the wear of monolithic zirconia crowns on antagonist teeth

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Zhenyu Tang ◽  
Xinyi Zhao ◽  
Hui Wang
Keyword(s):  
Epoxy Resin ◽  
Tetragonal Zirconia ◽  
Fatigue Wear ◽  
Posterior Teeth ◽  
Contact Points ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Natural Teeth ◽  
Monolithic Zirconia

Abstract Background The present study aimed to quantitate the wear of the highly transparent Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) ceramic monolithic zirconia crown on the enamel in vivo and discuss the prone position of the wear and the underlying mechanism. Methods A total of 43 patients with 43 posterior teeth were selected for full zirconia crown restoration and examined immediately, at 6 months, and at 1 year after restoration. During the follow-up visit, the fine impression of the patients’ monolithic zirconia crowns, the antagonist teeth, the corresponding contralateral natural teeth, the super plaster cast, and epoxy resin model was ontained. The model of epoxy resin was observed under a stereo microscope, and the microstructure parts were observed under a scanning electron microscope. Results After 1 year, the mean depth and volume of wearing of the monolithic zirconia crown were the smallest (all P < 0.01), while those of the antagonist teeth were significantly larger than those of the natural teeth (P < 0.0001), and no significant difference was found among the natural teeth (P = 0.3473, P = 0.6996). The amount of wear after one year was remarkably higher than that at 6 months (P < 0.0001). The microscopic observation revealed the tendency of wearing of the monolithic zirconia crown on the antagonist teeth at the protruding early contact points. Electron micrographs of tooth scars showed that the wearing mechanism of the monolithic zirconia crown on natural teeth was mainly abrasive and fatigue wear. Conclusions Although the self-wearing is insignificant, the monolithic zirconia crown can cause wear of the antagonist teeth via occlusal or early contact significantly; the amount of wearing is higher than that of natural teeth and increases over time. The wearing mechanism is mainly abrasive and fatigue wear.

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