scholarly journals Towards a New, Pre-Clinical, Subject-Independent Test Model for Kinematic Analysis after Total Knee Arthroplasty—Influence of the Proximo-Distal Patella Position and Patellar Tendon Stiffness

2021 ◽  
Vol 11 (21) ◽  
pp. 10322
Author(s):  
Adrian Sauer ◽  
Allan Maas ◽  
Svenja Ottawa ◽  
Alexander Giurea ◽  
Thomas M. Grupp
Keyword(s):  
Patellar Tendon ◽  
Test Method ◽  
Clinical Test ◽  
Research Approach ◽  
Fe Model ◽  
Test Model ◽  
Knee Prostheses ◽  
Tendon Stiffness ◽  
Patella Position

Although simulation models are heavily used in biomechanical research and testing of TKA implants, pre-clinical tools for a holistic estimation of implant performance under dynamic loading conditions are rare. The objective of this study was the development of an efficient pre-clinical test method for analyzing knee contact mechanics and kinematics based on a dynamic FE model and to evaluate the effects of the proximo-distal patella position and the patellar tendon stiffness on the patellar kinematics. A finite element-based workflow for knee prostheses designs was developed based on standardized in vivo load data, which included the tibial forces and moments. In a new research approach, the tibial forces are used as input for the model, whereas the tibial moments were used to validate the results. For the standardized sit down, stand up, and knee bend load cycles, the calculated tibial moments show only small deviations from the reference values—especially for high flexion angles. For the knee bend cycle, the maximum absolute value of patellar flexion decreases for higher patellar tendon stiffness and more distally placed patellar components. Therefore, patella-related clinical problems caused by patella baja may also arise if the patellar tendon is too weak for high tibiofemoral flexion angles.

Reproducibility and Workability of the European Test Standard EN 12791 Regarding the Effectiveness of Surgical Hand Antiseptics A Randomized, Multicenter Trial

2006 ◽  
Vol 27 (9) ◽  
pp. 935-939 ◽  
Author(s):  
Manfred Rotter ◽  
Michael Kundi ◽  
Miranda Suchomel ◽  
Hans-Peter Harke ◽  
Axel Kramer ◽  
...  
Keyword(s):  
Reduction Factor ◽  
Test Method ◽  
Test Model ◽  
Reference Formulation ◽  
In Vivo Test ◽  
Skin Flora ◽  
Hand Antisepsis ◽  
Viable Bacteria ◽  
The Mean

Objectives.To evaluate the reproducibility and workability of the in vivo test model of the European test standard EN 12791 regarding the effectiveness of surgical hand antiseptics and, as a secondary objective, to evaluate the power of the model to discriminate between the effectiveness of various formulations of surgical hand antiseptics.Design.Prospective, randomized, multicenter study with a Latin square design.Setting.Five laboratories at 2 universities, 2 disinfectant manufacturers, and 1 private testing institution.Participants.Twenty healthy adults in each laboratory.Intervention.Surgical hand antisepsis was performed by scrubbing with chlorhexidine gluconate 4% detergent (CHG) or by rubbing the hands with propan-2-OL (70% by volume; Iso 70) or ethanol 85% (E 85); rubbing the hands and forearms for 3 minutes with propan-1-OL (N 60) was used as the reference disinfection procedure. We deliberately chose to use these antiseptics at the given concentrations because they were intended to cover the range of typical antiseptics submitted for approval according to EN 12791.Methods.In once-weekly tests, the immediate effects of the 4 antiseptics were established according to the method laid down in EN 12791 by assessing the release of skin flora from the fingertips as viable bacteria counts per milliliter of sampling fluids before treatment and viable bacteria counts immediately after treatment, separately for both hands, such that after 4 weeks each volunteer had used every formulation once.Results.The mean log reduction factor (RF) for the release of bacterial skin flora (the log RF was calculated as the log count before treatment minus the log count after treatment) and corresponding standard deviations for the 4 hand antisepsis formulations were as follows: for CHG, 1.1 ± 0.3 colony-forming units (cfu) per milliliter of sampled fluid; for Iso 70, 1.7 ± 0.3 cfu/mL; for E 85, 2.1 ± 0.3 cfu/mL; and for N 60, 2.4 ± 0.4 cfu/mL. The differences between these values proved significant (P<.001) by analysis of variance and in Tukey's “honestly significantly different” (HSD) post hoc test. Although, with regard to their immediate antibacterial activity, the same ranking of these antiseptics was found at all laboratories, the levels of efficacy were significantly different across laboratories (P<.001); no statistical difference was found between left and right hands (P>.01). Relating the log RF values of the other 3 formulations to those of the reference formulation (N 60) abolished differences between laboratories (P = .16); in addition, the interclass correlation coefficient decreased from 9.1% to 4.5%. With 20 volunteers, a minimum difference of 0.47 log between the mean log RFs of the reference formulation and an inferior test formulation will be detected as significant at an α of .05 (1-sided) and a 1 — β value of .8.Conclusion.The test method described in EN 12791 yielded the same conclusion on the effectiveness of the tested formulations in every laboratory and proved, therefore, reproducible and workable.

scholarly journals In vivo Evaluation of Patellar Tendon Stiffness in Individuals with Patellofemoral Pain Syndrome

2008 ◽  
Vol 5 (2) ◽  
pp. 59-63
Author(s):  
Hsin-Yi Liu ◽  
Michelle Boling ◽  
Darin Padua ◽  
R. Alexander Creighton ◽  
Paul Weinhold
Keyword(s):  
Patellar Tendon ◽  
Pain Syndrome ◽  
Patellofemoral Pain Syndrome ◽  
Knee Extension ◽  
Patellofemoral Pain ◽  
Knee Extensors ◽  
Ultrasonic Technique ◽  
In Vivo Evaluation ◽  
Tendon Stiffness

The objective of this study was to utilise an ultrasonic technique to assess the effect of patellofemoral pain syndrome (PFPS) on the mechanical properties of the patellar tendon. Seven subjects with PFPS and seven matched control subjects volunteered to participate in this study. Subjects were asked to perform isometric maximal voluntary contractions of the knee extensors while their knee extension torque was monitored and the displacement of the patellar tendon was recorded with an ultrasonic system. Our results showed significantly lower tendon stiffness (by ∼30%) in the PFPS subjects. Although tendon secant modulus was lower by 34% in the PFPS subjects, the difference was not statistically significant. Therefore, we conclude that the ultrasonic technique was able to detect a decrease in the structural stiffness of the patellar tendon associated with PFPS. The decrease in tendon stiffness was moderately correlated with the length of symptoms in these individuals.

scholarly journals In vivo evaluation of patellar tendon stiffness in individuals with patellofemoral pain syndrome

2008 ◽  
Vol 5 (2) ◽  
pp. 59-63
Author(s):  
Hsin-Yi Liu ◽  
Michelle Boling ◽  
Darin Padua ◽  
R. Alexander Creighton ◽  
Paul Weinhold
Keyword(s):  
Patellar Tendon ◽  
Pain Syndrome ◽  
Patellofemoral Pain Syndrome ◽  
Patellofemoral Pain ◽  
In Vivo Evaluation ◽  
Tendon Stiffness

scholarly journals Lower tendon stiffness in very old compared with old individuals is unaffected by short-term resistance training of skeletal muscle

2018 ◽  
Vol 125 (1) ◽  
pp. 205-214 ◽  
Author(s):  
Christian Skou Eriksen ◽  
Cecilie Henkel ◽  
Rene B. Svensson ◽  
Anne-Sofie Agergaard ◽  
Christian Couppé ◽  
...  
Keyword(s):  
Physical Activity ◽  
Mechanical Properties ◽  
Resistance Training ◽  
Patellar Tendon ◽  
Cross Sectional ◽  
Tendon Stiffness ◽  
Very Old ◽  
Reduced Physical Activity ◽  
Heavy Resistance Training

Aging negatively affects collagen-rich tissue, like tendons, but in vivo tendon mechanical properties and the influence of physical activity after the 8th decade of life remain to be determined. This study aimed to compare in vivo patellar tendon mechanical properties in moderately old (old) and very old adults and the effect of short-term resistance training. Twenty old (9 women, 11 men, >65 yr) and 30 very old (11 women, 19 men, >83 yr) adults were randomly allocated to heavy resistance training (HRT) or no training (CON) and underwent testing of in vivo patellar tendon (PT) mechanical properties and PT dimensions before and after a 3-mo intervention. Previous measurements of muscle properties, blood parameters, and physical activity level were included in the analysis. Data from 9 old HRT, 10 old CON, 14 very old CON, and 12 old HRT adults were analyzed. In addition to lower quadriceps muscle strength and cross-sectional area (CSA), we found lower PT stiffness and Young’s modulus ( P < 0.001) and a trend toward the lower mid-portion PT-CSA ( P = 0.09) in very old compared with old subjects. Daily step count was also lower in very old subjects ( P < 0.001). Resistance training improved muscle strength and cross-sectional area equally in old and very old subjects ( P < 0.05) but did not affect PT mechanical properties or dimension. We conclude that PT material properties are reduced in very old age, and this may likely be explained by reduced physical activity. Three months of resistance training however, could not alter PT mechanical properties in very old individuals. NEW & NOTEWORTHY This research is the first to quantify in vivo tendon mechanical properties in a group of very old adults in their eighties. Patellar tendon stiffness was lower in very old (87 yr on average) compared with moderately old (68 yr on average) individuals. Reduced physical activity with aging may explain some of the loss in tendon stiffness, but regular heavy resistance training for 3 mo was not sufficient to change tendon mechanical properties.

Hemophilic Bledding Evaluated by Blood Pool Scanning

1981 ◽  
Vol 45 (03) ◽  
pp. 208-210 ◽  
Author(s):  
D Green ◽  
S M Spies ◽  
N A Rana ◽  
J W Milgram ◽  
R Mintzer
Keyword(s):  
Blood Volume ◽  
Blood Pool ◽  
Invasive Technique ◽  
Scintillation Camera ◽  
Knee Prostheses ◽  
Hemophilic Patient ◽  
Chronic Arthropathy ◽  
Image Density ◽  
Regional Blood Volume

SummaryThe technique of blood pool scanning was used to examine 15 hemophilic subjects. Employing an in vivo method for erythrocyte labeling with Technetium-99 m, a dynamic perfusion sequence is obtained using a scintillation camera positioned over the area to be examined. This demonstrates the vascularity of the tissue. Subsequently, equilibrium blood pool images of the area are obtained and analyzed with a densitometer to assess relative regional blood volume. In patients who were not bleeding but had chronic arthropathy, vascularity was not increased, and the blood volume of comparable joints was similar. By contrast, marked increases in vascularity and image density were observed in studies of acutely bleeding joints. Chronic hemarthroses were associated with persistent, but less marked increases in joint perfusion. Transient increases in joint vascularity were demonstrated after insertion of knee prostheses. In a patient with a thigh hematoma, the dimensions of the hemorrhage were clearly delineated. Since only a tracer dose of nuclide is infused intravenously, there are no allergic reactions or other side effects of the procedure. Blood pool scanning is a safe, non-invasive technique that augments clinical and radiographic evaluations, and provides a new dimension in the assessment of the hemophilic patient.

scholarly journals Computational Investigation of Transmural Differences in Left Ventricular Contractility

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Hua Wang ◽  
Xiaoyan Zhang ◽  
Shauna M. Dorsey ◽  
Jeremy R. McGarvey ◽  
Kenneth S. Campbell ◽  
...  
Keyword(s):  
Myocardial Contractility ◽  
Ex Vivo ◽  
Experimental Studies ◽  
Contractile Force ◽  
Left Ventricular ◽  
Lv Function ◽  
Fe Model ◽  
Myocardial Layers ◽  
Best Fit

Myocardial contractility of the left ventricle (LV) plays an essential role in maintaining normal pump function. A recent ex vivo experimental study showed that cardiomyocyte force generation varies across the three myocardial layers of the LV wall. However, the in vivo distribution of myocardial contractile force is still unclear. The current study was designed to investigate the in vivo transmural distribution of myocardial contractility using a noninvasive computational approach. For this purpose, four cases with different transmural distributions of maximum isometric tension (Tmax) and/or reference sarcomere length (lR) were tested with animal-specific finite element (FE) models, in combination with magnetic resonance imaging (MRI), pressure catheterization, and numerical optimization. Results of the current study showed that the best fit with in vivo MRI-derived deformation was obtained when Tmax assumed different values in the subendocardium, midmyocardium, and subepicardium with transmurally varying lR. These results are consistent with recent ex vivo experimental studies, which showed that the midmyocardium produces more contractile force than the other transmural layers. The systolic strain calculated from the best-fit FE model was in good agreement with MRI data. Therefore, the proposed noninvasive approach has the capability to predict the transmural distribution of myocardial contractility. Moreover, FE models with a nonuniform distribution of myocardial contractility could provide a better representation of LV function and be used to investigate the effects of transmural changes due to heart disease.

scholarly journals Modelling human skull growth: a validated computational model

2017 ◽  
Vol 14 (130) ◽  
pp. 20170202 ◽  
Author(s):  
Joseph Libby ◽  
Arsalan Marghoub ◽  
David Johnson ◽  
Roman H. Khonsari ◽  
Michael J. Fagan ◽  
...  
Keyword(s):  
Computational Model ◽  
Three Dimensional ◽  
Basic Knowledge ◽  
Fe Model ◽  
Adult Size ◽  
Fe Method ◽  
Percentage Difference ◽  
Skull Growth

During the first year of life, the brain grows rapidly and the neurocranium increases to about 65% of its adult size. Our understanding of the relationship between the biomechanical forces, especially from the growing brain, the craniofacial soft tissue structures and the individual bone plates of the skull vault is still limited. This basic knowledge could help in the future planning of craniofacial surgical operations. The aim of this study was to develop a validated computational model of skull growth, based on the finite-element (FE) method, to help understand the biomechanics of skull growth. To do this, a two-step validation study was carried out. First, an in vitro physical three-dimensional printed model and an in silico FE model were created from the same micro-CT scan of an infant skull and loaded with forces from the growing brain from zero to two months of age. The results from the in vitro model validated the FE model before it was further developed to expand from 0 to 12 months of age. This second FE model was compared directly with in vivo clinical CT scans of infants without craniofacial conditions ( n = 56). The various models were compared in terms of predicted skull width, length and circumference, while the overall shape was quantified using three-dimensional distance plots. Statistical analysis yielded no significant differences between the male skull models. All size measurements from the FE model versus the in vitro physical model were within 5%, with one exception showing a 7.6% difference. The FE model and in vivo data also correlated well, with the largest percentage difference in size being 8.3%. Overall, the FE model results matched well with both the in vitro and in vivo data. With further development and model refinement, this modelling method could be used to assist in preoperative planning of craniofacial surgery procedures and could help to reduce reoperation rates.

scholarly journals The combined effects of obesity and ageing on skeletal muscle function and tendon properties in vivo in men

Endocrine ◽  
2021 ◽  
Author(s):  
David J. Tomlinson ◽  
Robert M. Erskine ◽  
Christopher I. Morse ◽  
Joseph M. Pappachan ◽  
Emmanuel Sanderson-Gillard ◽  
...  
Keyword(s):  
Body Mass ◽  
Older Men ◽  
Normal Weight ◽  
Skeletal Muscle Function ◽  
Cross Sectional ◽  
Tendon Stiffness ◽  
Tnf Α ◽  
Combined Impact ◽  
Negative Relationships

Abstract Purpose We investigated the combined impact of ageing and obesity on Achilles tendon (AT) properties in vivo in men, utilizing three classification methods of obesity. Method Forty healthy, untrained men were categorised by age (young (18–49 years); older (50–80 years)), body mass index (BMI; normal weight (≥18.5–<25); overweight (≥25–<30); obese (≥30)), body fat% (normal adipose (<28%); high adiposity (≥28%)) and fat mass index (FMI; normal (3–6); excess fat (>6–9); high fat (>9). Assessment of body composition used dual-energy X-ray absorptiometry, gastrocnemius medialis (GM)/AT properties used dynamometry and ultrasonography and endocrine profiling used multiplex luminometry. Results Older men had lower total range of motion (ROM; −11%; P = 0.020), GM AT force (−29%; P < 0.001), stiffness (−18%; P = 0.041), Young’s modulus (−22%; P = 0.011) and AT stress (−28%; P < 0.001). All three methods of classifying obesity revealed obesity to be associated with lower total ROM (P = 0.014–0.039). AT cross sectional area (CSA) was larger with higher BMI (P = 0.030). However, after controlling for age, higher BMI only tended to be associated with greater tendon stiffness (P = 0.074). Interestingly, both AT CSA and stiffness were positively correlated with body mass (r = 0.644 and r = 0.520) and BMI (r = 0.541 and r = 0.493) in the young but not older adults. Finally, negative relationships were observed between AT CSA and pro-inflammatory cytokines TNF-α, IL-6 and IL-1β. Conclusions This is the first study to provide evidence of positive adaptations in tendon stiffness and size in vivo resulting from increased mass and BMI in young but not older men, irrespective of obesity classification.

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