In Vivo Observations of Hydraulic Stiffening in the Canine Femoral Head

1997 ◽  
Vol 119 (1) ◽  
pp. 103-108 ◽  
Author(s):  
J. A. Ochoa ◽  
A. P. Sanders ◽  
T. W. Kiesler ◽  
D. A. Heck ◽  
J. P. Toombs ◽  
...  
Keyword(s):  
Femoral Head ◽  
Femoral Neck ◽  
Boundary Conditions ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Femoral Cortex ◽  
Hind Limbs ◽  
Femoral Heads ◽  
Fluid Boundary

The role that intertrabecular contents and their boundary conditions have on the dynamic mechanical response of canine femoral heads was investigated in vivo. Femoral heads from paired intact hind limbs of canine specimens were subjected to a sinusoidal strain excitation, at physiologic frequencies, in the cranio-caudal direction. The fluid boundary conditions for the contralateral limbs were changed by predrilling through the lateral femoral cortex and into the femoral neck. The drilling procedure did not invade the head itself. This femoral head fluid boundary alteration reduced the stiffness by 19 percent for testing at 1 Hz. The results of this study demonstrate that fluid stiffening occurs in vivo as previously observed ex vivo.

Use of computed tomography to compare two femoral head and neck excision ostectomy techniques as performed by two novice veterinarians

2015 ◽  
Vol 28 (05) ◽  
pp. 295-300 ◽  
Author(s):  
M. D. O’Donnell ◽  
G. Bobe ◽  
R. P. Scholz ◽  
J. E. Wiest ◽  
S. Nemanic ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Femoral Head ◽  
Femoral Neck ◽  
Head And Neck ◽  
Clinical Setting ◽  
Ex Vivo ◽  
Bone Volume ◽  
Bone Trauma ◽  
Before And After ◽  
Bone Fragments

Summary Objectives: To compare the results of femoral head and neck excision (FHNE) ostectomy performed by two novice veterinarians using an osteotome and mallet or microsagittal saw. Methods: In this ex vivo cadaveric study, hindlimbs of eight canine cadavers were randomized to FHNE with osteotome or micro sagittal saw as performed by two recently graduated veterinarians. The hindimbs were imaged by computed tomography (CT) before and after the osteotomy. Post FHNE CT images were evaluated by a board certified radiologist blinded to the ostectomy technique for assessment of the number of bone fragments, fissures, smoothness of osteotomy margination, and volume of residual fe-moral neck. Results: Femoral head and neck excision performed with the osteotome produced more peri-ostectomy bone fragments, cortical fissures, irregular margins, and residual femoral neck volume, compared with osteotomy using a saw. Clinical relevance: Compared to FHNE performed with a sagittal saw, osteotome FHNE resulted in a greater bone trauma and residual neck bone volume, which would require post-ostectomy modification in a clinical setting.

Viscoelastic Characterization of Perfused Liver: Indentation Testing and Preliminary Modeling

2007 ◽  
Author(s):  
Amy E. Kerdok ◽  
Robert D. Howe ◽  
Simona Socrate
Keyword(s):  
Constitutive Model ◽  
Multiple Testing ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Unknown Boundary ◽  
Abdominal Organs ◽  
Rheological Modeling ◽  
Unknown Boundary Conditions ◽  
Surgical Manipulation

Computer-aided medical technologies are currently restricted by the limited understanding of the mechanical response of solid abdominal organs to finite loading conditions typical of surgical manipulation [5]. This limitation is a result of the difficulty in acquiring the necessary data on whole organs. To develop a constitutive model capable of predicting complex surgical scenarios, multiple testing modalities need to be simultaneously obtained to capture the fundamental nature of the tissue’s behavior under such conditions. In vivo tests are essential to obtain a realistic response, but their inherent difficulty and unknown boundary conditions makes them an impractical approach. Ex vivo tests are easy to control, but the response is unrealistic. A perfusion apparatus was previously developed that obtained near in vivo conditions for whole livers while allowing the ease of ex vivo testing [3]. This work presents the results from complete viscoelastic testing of whole-perfused livers with surgically relevant time-dependant indentation loading profiles to 35% nominal strain. These results will aid in the development of a constitutive model for the liver whose parameters can be related to the physical constituents of the tissue. As an intermediate modeling step, a 1D rheological modeling tool was used to identify the form and initial parameters for a constitutive model.

scholarly journals Characterization of rat tail lymphatic contractility and biomechanics: incorporating nitric oxide-mediated vasoregulation

2020 ◽  
Vol 17 (170) ◽  
pp. 20200598 ◽  
Author(s):  
Mohammad S. Razavi ◽  
J. Brandon Dixon ◽  
Rudolph L. Gleason
Keyword(s):  
Nitric Oxide ◽  
Mechanical Response ◽  
Contractile Function ◽  
Ex Vivo ◽  
Biomechanical Model ◽  
Biomechanical Models ◽  
Lymphatic Pumping ◽  
Rat Tail ◽  
Lymphatic Contractility

The lymphatic system transports lymph from the interstitial space back to the great veins via a series of orchestrated contractions of chains of lymphangions. Biomechanical models of lymph transport, validated with ex vivo or in vivo experimental results, have proved useful in revealing novel insight into lymphatic pumping; however, a need remains to characterize the contributions of vasoregulatory compounds in these modelling tools. Nitric oxide (NO) is a key mediator of lymphatic pumping. We quantified the active contractile and passive biaxial biomechanical response of rat tail collecting lymphatics and changes in the contractile response to the exogenous NO administration and integrated these findings into a biomechanical model. The passive mechanical response was characterized with a three-fibre family model. Nonlinear regression and non-parametric bootstrapping were used to identify best-fit material parameters to passive cylindrical biaxial mechanical data, assessing uniqueness and parameter confidence intervals; this model yielded a good fit ( R 2 = 0.90). Exogenous delivery of NO via sodium nitroprusside (SNP) elicited a dose-dependent suppression of contractions; the amplitude of contractions decreased by 30% and the contraction frequency decreased by 70%. Contractile function was characterized with a modified Rachev–Hayashi model, introducing a parameter that is related to SNP concentration; the model provided a good fit ( R 2 = 0.89) to changes in contractile responses to varying concentrations of SNP. These results demonstrated the significant role of NO in lymphatic pumping and provide a predictive biomechanical model to integrate the combined effect of mechanical loading and NO on lymphatic contractility and mechanical response.

scholarly journals The Characteristic Recovery Time as a Novel, Noninvasive Metric for Assessing In Vivo Cartilage Mechanical Function

2020 ◽  
Vol 48 (12) ◽  
pp. 2901-2910 ◽  
Author(s):  
Hattie C. Cutcliffe ◽  
Keithara M. Davis ◽  
Charles E. Spritzer ◽  
Louis DeFrate
Keyword(s):  
Mechanical Property ◽  
Relaxation Time ◽  
Recovery Time ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Cartilage Thickness ◽  
Mechanical Function ◽  
Mechanical State ◽  
T2 Relaxation

AbstractOsteoarthritis (OA) is a disease characterized by the degeneration of cartilage tissue, and is a leading cause of disability in the United States. The clinical diagnosis of OA includes the presence of pain and radiographic imaging findings, which typically do not present until advanced stages of the disease when treatment is difficult. Therefore, identifying new methods of OA detection that are sensitive to earlier pathological changes in cartilage, which may be addressed prior to the development of irreversible OA, is critical for improving OA treatment. A potentially promising avenue for developing early detection methods involves measuring the tissue’s in vivo mechanical response to loading, as changes in mechanical function are commonly observed in ex vivo studies of early OA. However, thus far the mechanical function of cartilage has not been widely assessed in vivo. Therefore, the purpose of this study was to develop a novel methodology that can be used to measure an in vivo mechanical property of cartilage: the characteristic recovery time. Specifically, in this study we quantified the characteristic recovery time of cartilage thickness after exercise in relatively young subjects with asymptomatic cartilage. Additionally, we measured baseline cartilage thickness and T1rho and T2 relaxation times (quantitative MRI) prior to exercise in these subjects to assess whether baseline MRI measures are predictive of the characteristic recovery time, to understand whether or not the characteristic recovery time provides independent information about cartilage’s mechanical state. Our results show that the mean recovery strain response across subjects was well-characterized by an exponential approach with a characteristic time of 25.2 min, similar to literature values of human characteristic times measured ex vivo. Further, we were unable to detect a statistically significant linear relationship between the characteristic recovery time and the baseline metrics measured here (T1rho relaxation time, T2 relaxation time, and cartilage thickness). This might suggest that the characteristic recovery time has the potential to provide additional information about the mechanical state of cartilage not captured by these baseline MRI metrics. Importantly, this study presents a noninvasive methodology for quantifying the characteristic recovery time, an in vivo mechanical property of cartilage. As mechanical response may be indicative of cartilage health, this study underscores the need for future studies investigating the characteristic recovery time and in vivo cartilage mechanical response at various stages of OA.

scholarly journals Optimization and Validation of a Human Ex Vivo Femoral Head Model for Preclinical Cartilage Research and Regenerative Therapies

Cartilage ◽  
2020 ◽  
pp. 194760352093453
Author(s):  
Katarzyna Styczynska-Soczka ◽  
Anish K. Amin ◽  
A. Hamish W. Simpson ◽  
Andrew C. Hall
Keyword(s):  
Surface Roughness ◽  
Femoral Head ◽  
Alcian Blue ◽  
Cartilage Repair ◽  
Ex Vivo ◽  
Chondrocyte Viability ◽  
Femoral Heads ◽  
Regenerative Therapies ◽  
Picrosirius Red ◽  
And Cartilage

Objective Articular cartilage is incapable of effective repair following injury or during osteoarthritis. While there have been developments in cartilage repair technologies, there is a need to advance biologically relevant models for preclinical testing of biomaterial and regenerative therapies. This study describes conditions for the effective ex vivo culture of the whole human femoral head. Design Fresh, viable femoral heads were obtained from femoral neck fractures and cultured for up to 10 weeks in (a) Dulbecco’s modified Eagle’s medium (DMEM); (b) DMEM + mixing; (c) DMEM + 10% human serum (HS); (d) DMEM + 10% HS + mixing. The viability, morphology, volume, and density of fluorescently labelled in situ chondrocytes and cartilage surface roughness were assessed by confocal microscopy. Cartilage histology was studied for glycosaminoglycan content using Alcian blue and collagen content using picrosirius red. Results Chondrocyte viability remained at >95% in DMEM + 10% HS. In DMEM alone, viability remained high for ~4 weeks and then declined. For the other conditions, superficial zone chondrocyte viability fell to <35% at 10 weeks with deeper zones being relatively unaffected. In DMEM + 10% HS at 10 weeks, the number of chondrocytes possessing cytoplasmic processes increased compared with DMEM ( P = 0.017). Alcian blue labeling decreased ( P = 0.02) and cartilage thinned ( P ≤ 0.05); however, there was no change to surface roughness, chondrocyte density, chondrocyte volume, or picrosirius red labeling ( P > 0.05). Conclusions In this ex vivo model, chondrocyte viability was maintained in human femoral heads for up to 10 weeks in culture, a novel finding not previously reported. This human model could prove invaluable for the exploration, development, and assessment of preclinical cartilage repair and regenerative therapies.

scholarly journals Mechanical Response Changes in Porcine Tricuspid Valve Anterior Leaflet Under Osmotic-Induced Swelling

2019 ◽  
Vol 6 (3) ◽  
pp. 70 ◽  
Author(s):  
Samuel D. Salinas ◽  
Margaret M. Clark ◽  
Rouzbeh Amini
Keyword(s):  
Tricuspid Valve ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Control Group ◽  
Anterior Leaflet ◽  
Buffer Solution ◽  
Tissue Samples ◽  
The Impact

Since many soft tissues function in an isotonic in-vivo environment, it is expected that physiological osmolarity will be maintained when conducting experiments on these tissues ex-vivo. In this study, we aimed to examine how not adhering to such a practice may alter the mechanical response of the tricuspid valve (TV) anterior leaflet. Tissue specimens were immersed in deionized (DI) water prior to quantification of the stress–strain responses using an in-plane biaxial mechanical testing device. Following a two-hour immersion in DI water, the tissue thickness increased an average of 107.3% in the DI water group compared to only 6.8% in the control group, in which the tissue samples were submerged in an isotonic phosphate buffered saline solution for the same period of time. Tissue strains evaluated at 85 kPa revealed a significant reduction in the radial direction, from 34.8% to 20%, following immersion in DI water. However, no significant change was observed in the control group. Our study demonstrated the impact of a hypo-osmotic environment on the mechanical response of TV anterior leaflet. The imbalance in ions leads to water absorption in the valvular tissue that can alter its mechanical response. As such, in ex-vivo experiments for which the native mechanical response of the valves is important, using an isotonic buffer solution is essential.

scholarly journals A biphasic multilayer computational model of human skin

2021 ◽  
Author(s):  
David Sachs ◽  
Adam Wahlsten ◽  
Sebastian Kozerke ◽  
Gaetana Restivo ◽  
Edoardo Mazza
Keyword(s):  
Human Skin ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Direct Consequence ◽  
Tensile Tests ◽  
Deformation Pattern ◽  
Reticular Dermis ◽  
Biphasic Model ◽  
Dermal Thickness

AbstractThe present study investigates the layer-specific mechanical behavior of human skin. Motivated by skin’s histology, a biphasic model is proposed which differentiates between epidermis, papillary and reticular dermis, and hypodermis. Inverse analysis of ex vivo tensile and in vivo suction experiments yields mechanical parameters for each layer and predicts a stiff reticular dermis and successively softer papillary dermis, epidermis and hypodermis. Layer-specific analysis of simulations underlines the dominating role of the reticular dermis in tensile loading. Furthermore, it shows that the observed out-of-plane deflection in ex vivo tensile tests is a direct consequence of the layered structure of skin. In in vivo suction experiments, the softer upper layers strongly influence the mechanical response, whose dissipative part is determined by interstitial fluid redistribution within the tissue. Magnetic resonance imaging-based visualization of skin deformation in suction experiments confirms the deformation pattern predicted by the multilayer model, showing a consistent decrease in dermal thickness for large probe opening diameters.

scholarly journals Evaluation of in vivo wear of vitamin E-diffused highly crosslinked polyethylene at five years

2018 ◽  
Vol 100-B (12) ◽  
pp. 1592-1599 ◽  
Author(s):  
V. P. Galea ◽  
J. W. Connelly ◽  
B. Shareghi ◽  
J. Kärrholm ◽  
O. Sköldenberg ◽  
...  
Keyword(s):  
Vitamin E ◽  
Femoral Head ◽  
Clinical Results ◽  
Patient Reported Outcome Measures ◽  
Patient Reported Outcome ◽  
Wear Properties ◽  
Ceramic Femoral Head ◽  
Patient Reported ◽  
Femoral Heads

Aims The primary aim of this study was to compare the wear properties of vitamin E-diffused, highly crosslinked polyethylene (VEPE) and one formulation of moderately crosslinked and mechanically annealed ultra-high molecular weight polyethylene (ModXLPE) in patients five years after primary total hip arthroplasty (THA). The secondary aim was to assess the clinical results of patients treated with VEPE by evaluating patient-reported outcome measures (PROMs), radiological evidence of fixation, and the incidence of mechanical failure. Patients and Methods A total of 208 patients (221 THAs) from four international centres were recruited into a prospective study involving radiostereometric analysis (RSA) and the assessment of clinical outcomes. A total of 193 hips (87%) were reviewed at the five-year follow-up. Of these, 136 (70%) received VEPE (vs ModXLPE) liners and 68 (35%) received ceramic (vs metal) femoral heads. PROMs and radiographs were collected preoperatively and at one, two, and five years postoperatively. In addition, RSA images were collected to measure PE wear postoperatively and at one, two, and five years after surgery. Results We observed similar bedding in one year postoperatively and wear two years postoperatively between the two types of liner. However, there was significantly more penetration of the femoral head in the ModXLPE cohort compared with the VEPE cohort five years postoperatively (p < 0.001). The only variables independently predictive of increased wear were ModXLPE (vs VEPE) liner type (β = 0.22, p = 0.010) and metal (vs ceramic) femoral head (β = 0.21, p = 0.013). There was no association between increased wear and the development of radiolucency (p = 0.866) or PROMs. No patient had evidence of osteolysis. Conclusion Five years postoperatively, patients with VEPE (vs ModXLPE) and ceramic (vs metal) femoral heads had decreased wear. The rates of wear for both liners were very low and have not led to any osteolysis or implant failure due to aseptic loosening.

Early acetabular cartilage wear following hemiarthroplasty: An ovine model

2016 ◽  
Vol 29 (02) ◽  
pp. 125-130
Author(s):  
Stuart Callary ◽  
Lucian Solomon ◽  
Roumen Stamenkov ◽  
Margaret McGee ◽  
Donald Howie ◽  
...  
Keyword(s):  
Femoral Head ◽  
Ex Vivo ◽  
Standard Technique ◽  
Histological Evaluation ◽  
Radiographic Measurement ◽  
Acetabular Cartilage ◽  
Radiostereometric Analysis ◽  
Ovine Model ◽  
Cartilage Wear

SummaryObjectives: Hemiarthroplasty induces degenerative changes in the hip joint, which are difficult to evaluate in vivo. Radiostereometric analysis (RSA) is a radiographic measurement technique that has recently been used to measure acetabular cartilage wear in vivo. The aim of the study was to measure acetabular cartilage wear, using this technique, in an ovine model during the first 14 weeks post-implantation.Methods: Measurements of three-dimensional femoral head migration, combined with visual assessments at necropsy and safranin O staining for cartilage integrity, were undertaken.Results: Mean femoral head migration during the first six weeks was 0.525 mm in the medial, 0.144 mm in the cranial, and 0.517 mm in the dorsal direction. The majority of this migration was confirmed to be cartilage wear in the medial and dorsal aspects of the acetabulum at necropsy and with subsequent histological evaluation depicting significant cartilage degeneration.Clinical significance: Radiostereometric analysis is the current gold standard technique for in vivo assessment of implant migration following total hip replacement. This study has utilized RSA to quantify the amount of early cartilage wear in vivo, which was supported by ex vivo evaluations. Accurately measuring the amount of cartilage wear will allow future studies to compare component material and design characteristics prior to clinical use.

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

Sign in / Sign up

Export Citation Format

Share Document