Heat Generation and Dissipation Behavior of Various Orthopaedic Bearing Materials

2006 ◽  
Vol 309-311 ◽  
pp. 1281-1284 ◽  
Author(s):  
Stanley Tsai ◽  
Abraham Salehi ◽  
Patrick Aldinger ◽  
Gordon Hunter
Keyword(s):  
Femoral Head ◽  
Peak Load ◽  
Tetragonal Zirconia ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Interface Surface ◽  
Hip Simulator ◽  
Significant Difference ◽  
Femoral Heads ◽  
Oxidized Zirconium ◽  
Bearing Materials

It has been shown that with high interfacial temperatures in hip bearings, it is possible to precipitate proteins, greatly reduce the compressive creep properties of ultrahigh molecular weight polyethylene (UHMWPE), and change the phase content of monolithic tetragonal zirconia. These induced features may alter the wear rate of UHMWPE. It was the objective of this study to examine the interfacial temperatures of oxidized zirconium (OxZr) heads as compared with metallic and ceramic heads coupled with polyethylene in a hip simulator. The interface temperatures were measured by placing thermocouples within 0.5 mm of the interface surface of both femoral heads and acetabular liners, and then articulating the surfaces using a 12-station AMTI anatomic hip simulator. The alumina femoral heads had the lowest average interfacial temperature, followed in increasing order by OxZr, CoCr, and zirconia. The ranking corresponds to the thermal conductivity of each material. A statistically significant difference (p<0.05) was found between all four materials for the femoral head temperature. No difference was seen in liner temperature between the alumina and OxZr groups, but statistical differences were found between all other combinations. Additionally, increasing head diameter, peak load, cyclic frequency, and serum concentration all resulted in statistically significant increases in both femoral head and liner temperatures.

scholarly journals Atraumatic femoral head necrosis: a biomechanical, histological and radiological examination compared to primary hip osteoarthritis

2021 ◽  
Author(s):  
Hofmann Alexander ◽  
Fischer Benjamin ◽  
Schleifenbaum Stefan ◽  
Kurz Sascha ◽  
Edel Melanie ◽  
...  
Keyword(s):  
Bone Density ◽  
Femoral Head ◽  
Hip Osteoarthritis ◽  
Head Group ◽  
Common Disease ◽  
Stress Tests ◽  
Value Analysis ◽  
Femoral Neck Axis ◽  
Significant Difference ◽  
Femoral Heads

Abstract Introduction Atraumatic necrosis of the femoral head (AFHN) is a common disease with an incidence of 5000–7000 middle-aged adults in Germany. There is no uniform consensus in the literature regarding the configuration of the bone in AFHN. The clinical picture of our patients varies from very hard bone, especially in idiopathic findings, and rather soft bone in cortisone-induced necrosis. A better understanding of the underlying process could be decisive for establishing a morphology-dependent approach. The aim of this study is the closer examination of the condition of the bone in the AFHN compared to the primary hip osteo arthritis (PHOA). Materials and methods The preparations were obtained as part of elective endoprosthetic treatment of the hip joint. Immediately after sample collection, thin-slice CT of the preserved femoral heads was performed to determine the exact density of the bone in the necrosis zone. Reconstruction was done in 0.8–1 mm layers in two directions, coronary and axial, starting from the femoral neck axis. Density of the femoral heads was determined by grey value analysis. The value in Hounsfield units per sample head was averaged from three individual measurements to minimize fluctuations. For biomechanical and histomorphological evaluation, the samples were extracted in the load bearing zone perpendicular to the surface of the femoral head. Group-dependent statistical evaluation was performed using single factor variance analysis (ANOVA). Results A total of 41 patients with a mean age of 64.44 years were included. The mean bone density of the AFHN samples, at 1.432 g/cm3, was about 7% higher than in the PHOA group with a mean value of 1.350 g/cm3 (p = 0.040). The biomechanical testing in the AFHN group showed a 22% higher—but not significant—mean compressive strength (20.397 MPa) than in the PHOA group (16.733 MPa). On the basis of histological analysis, no differentiation between AFHN and PHOA samples was possible. Conclusions The present study (NCT, evidence level II) shows that AFHN has a very well detectable higher bone density compared to PHOA. However, neither biomechanical stress tests nor histomorphological evaluation did show any significant difference between the groups. The results allow the conclusion that there is no “soft” necrosis at all in the AFHN group.

scholarly journals Insufficient blood supply of fovea capitis femoris, a risk factor of femoral head osteonecrosis

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Keyang Zhao ◽  
Fangfang Zhang ◽  
Kun Quan ◽  
Bin Zhu ◽  
Guangyi Li ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Femoral Head ◽  
Blood Supply ◽  
Maximum Diameter ◽  
Head Group ◽  
Minimum Diameter ◽  
Nutrient Foramen ◽  
Nutrient Foramina ◽  
Significant Difference ◽  
Femoral Heads

Abstract Background A defective nutrient foramen in the fovea capitis femoris was hypothesized to reflect the blood circulation pattern of the femoral head, leading to insufficient blood supply and causing osteonecrosis of the femoral head. Methods Normal and necrotic femoral head specimens were collected. The necrotic femoral head group was divided into a non-traumatic and traumatic subgroup. 3D scanning was applied to read the number, the diameter, and the total cross-sectional area of the nutrient foramina in the fovea capitis femoris. Chi-squared tests and independent t-tests were used to detect any differences in the categorical and continuous demographic variables. Logistic regression models were used to estimate the odds ratio (OR) for non-traumatic and traumatic osteonecrosis in different characteristic comparisons. Results A total of 249 femoral head specimens were collected, including 100 normal femoral heads and 149 necrotic femoral heads. The necrotic femoral head group revealed a significantly higher percentage of no nutrient foramen (p < 0.001), a smaller total area of nutrient foramina (p < 0.001), a smaller mean area of nutrient foramina (p = 0.014), a lower maximum diameter of the nutrient foramen (p < 0.001), and a lower minimum diameter of the nutrient foramen (p < 0.001) than the normal femoral head group. The logistic regression model demonstrated an increasing number of nutrient foramina (crude OR, 0.51; p < 0.001), a larger total area of nutrient foramina (crude OR, 0.58; p < 0.001), a larger mean area of nutrient foramina (crude OR, 0.52; p = 0.023), a greater maximum diameter of the nutrient foramen (crude OR, 0.26; p < 0.001), and greater minimum diameter of the nutrient foramen (crude OR, 0.20; p < 0.001) significantly associated with reduced odds of osteonecrosis of the femoral head (ONFH). The necrotic femoral head group was further divided into 118 non-traumatic and 31 traumatic necrotic subgroups, and no significant difference was observed in any characteristics between them. Conclusions Characteristics of the nutrient foramen in the fovea capitis femoris showed a significant defect of necrotic than normal femoral heads, and significantly reduced odds were associated with the higher abundance of the nutrient foramen in ONFH. Therefore, the condition of the nutrient foramen might be the indicator of ONFH.

Holding Power of Orthopaedic Screws in Bovine Femoral Heads

1993 ◽  
Vol 06 (03) ◽  
pp. 160-162 ◽  
Author(s):  
M. J. Ulm ◽  
D. G. Wilson
Keyword(s):  
Femoral Head ◽  
Cannulated Screws ◽  
Cancellous Screw ◽  
Holding Power ◽  
Cortical Screw ◽  
Femoral Heads ◽  
Cancellous Screws ◽  
Physeal Fractures

SummaryFemoral capital physeal fractures have been successfully repaired using 7.0 mm cannulated screws. The holding power of 7.0 mm cannulated screws was compared to the holding power of 5.5 mm cortical screws and 6.5 mm cancellous screws using paired bovine femoral heads. The 7.0 mm cannulated screw’s holding power was superior to the 6.5 mm cancellous screw and similar to that of the 5.5 mm cortical screw.When placed in the bovine femoral head, 7.0 mm cannulated screws have holding power greater than 6.5 mm cancellous screws and similar to 5.5 mm cortical screws.

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

A comparison of 2 cementing techniques in hip resurfacing using human femoral heads

2021 ◽  
pp. 112070002199706
Author(s):  
Sarah J Shiels ◽  
Martin Williams ◽  
Gordon C Bannister ◽  
Richard P Baker
Keyword(s):  
Femoral Head ◽  
Femoral Component ◽  
Bubble Formation ◽  
Young Male ◽  
Cement Mantle ◽  
Hip Resurfacing ◽  
Air Bubble ◽  
Low Viscosity ◽  
Femoral Heads ◽  
Group 2

Introduction: Hip resurfacing remains a valid option in young male patients. The creation of the optimum cement mantle aids fixation of the femoral component. If the cement mantle is too thick the prosthesis can remain proud leading to early failure or if it penetrates too far into the femoral head, it may cause osteonecrosis. Method: 18 of 96 femoral heads collected from patients undergoing total hip arthroplasty were matched for their surface porosity. They were randomly allocated into 2 different cementing groups. Group 1 had the traditional bolus of cement technique, while group 2 had a modified cementing technique (swirl) where the inside of the femoral component was lined with an even layer of low viscosity cement. Results: The traditional bolus technique had significantly greater cement mantle thickness in 3 of 4 zones of penetration ( p = 0.002), greater and larger air bubble formation (6 of 9 in bolus technique vs. 1 in 9 in swirl technique, p = 0.05) and more incomplete cement mantles compared with the swirl technique. There was no relationship to femoral head porosity. Conclusion: The swirl technique should be used to cement the femoral component in hip resurfacing. Long-term clinical studies would conform if this translates into increased survivorship of the femoral component.

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.

scholarly journals Metacarpal shaft fixation: a biomechanical comparison of dorsal plating, lag screws, and headless compression screws

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Felix G. E. Dyrna ◽  
Daniel M. Avery ◽  
Ryu Yoshida ◽  
David Lam ◽  
Simon Oeckenpöhler ◽  
...  
Keyword(s):  
Peak Load ◽  
Rigid Fixation ◽  
Advantages And Disadvantages ◽  
Shaft Fractures ◽  
Metacarpal Shaft ◽  
Significant Difference ◽  
Load To Failure ◽  
Headless Compression Screws ◽  
Diaphyseal Fractures ◽  
Dorsal Plating

Abstract Background Metacarpal shaft fractures are common and can be treated nonoperatively. Shortening, angulation, and rotational deformity are indications for surgical treatment. Various forms of treatment with advantages and disadvantages have been documented. The purpose of the study was to determine the stability of fracture fixation with intramedullary headless compression screws in two types of metacarpal shaft fractures and compare them to other common forms of rigid fixation: dorsal plating and lag screw fixation. It was hypothesized that headless compression screws would demonstrate a biomechanical stronger construct. Methods Five matched paired hands (age 60.9 ± 4.6 years), utilizing non-thumb metacarpals, were used for comparative fixation in two fracture types created by an osteotomy. In transverse diaphyseal fractures, fixation by headless compression screws (n = 7) and plating (n = 8) were compared. In long oblique diaphyseal fractures, headless compression screws (n = 8) were compared with plating (n = 8) and lag screws (n = 7). Testing was performed using an MTS frame producing an apex dorsal, three point bending force. Peak load to failure and stiffness were calculated from the load-displacement curve generated. Results For transverse fractures, headless compression screws had a significantly higher stiffness and peak load to failure, means 249.4 N/mm and 584.8 N, than plates, means 129.02 N/mm and 303.9 N (both p < 0.001). For long oblique fractures, stiffness and peak load to failure for headless compression screws were means 209 N/mm and 758.4 N, for plates 258.7 N/mm and 518.5 N, and for lag screws 172.18 N/mm and 234.11 N. There was significance in peak load to failure for headless compression screws vs plates (p = 0.023), headless compression screws vs lag screws (p < 0.001), and plates vs lag screws (p = 0.009). There was no significant difference in stiffness between groups. Conclusion Intramedullary fixation of diaphyseal metacarpal fractures with a headless compression screw provides excellent biomechanical stability. Coupled with lower risks for adverse effects, headless compression screws may be a preferable option for those requiring rapid return to sport or work. Level of evidence Basic Science Study, Biomechanics.

Effect of Micro-Manufacturing Processes on Surface Behavior

2007 ◽  
Author(s):  
Tiffany Davis ◽  
Jian Cao ◽  
Wei Chen ◽  
Q. Jane Wang ◽  
Cedric Xia ◽  
...  
Keyword(s):  
Surface Texture ◽  
Surface Texturing ◽  
Steel Sample ◽  
Laser Surface ◽  
Laser Surface Texturing ◽  
Copper Sheet ◽  
Property Variation ◽  
Nano Indentation ◽  
Interface Surface ◽  
Significant Difference

Surface texturing has become a valuable technique for reducing friction and wear in contacting parts; laser surface texturing is one such method used to create micro-dimples on the interface surface. This work investigates the surface material property variation caused by laser surface texturing. The hardness and modulus of elasticity of a steel laser surface texture sample were evaluated near the dimples and away from the dimpled zone through nano-indentation. Resulting data shows that no significant difference exists between the material properties from the two positions. An alternate technique for surface texture generation was also explored, involving the use of micro-punches to create surface features in a metal sample. Computational simulations were performed using a second material underneath a thin copper sheet. The second material was present to serve as a support and to allow extensive deformation of the top material. The choice of the support material and ratio of material thicknesses was optimized to minimize pile up. Trials were conducted for three base supporting materials: PTFE, PMMA, and aluminum. Results show that PMMA performed better than the other materials. Positive deflection was minimized when the PMMA thickness was at least fifteen times that of the copper sheet. Physical experiments were completed with a thin copper sheet to verify the results. An array of micro-indentations was also created in a bulk steel sample. In order to assess the effect of dimpling via micro-forming, nano-indentation was performed near and far from the deformed material of the dimples. Similar to the laser textured sample, no significant differences were found between the two locations.

scholarly journals Microvascular Density of Rapidly Destructive Arthropathy of the Hip Joint

2005 ◽  
Vol 13 (1) ◽  
pp. 40-45 ◽  
Author(s):  
T Yamakawa ◽  
A Sudo ◽  
M Tanaka ◽  
A Uchida
Keyword(s):  
Femoral Head ◽  
Hip Joint ◽  
Joint Destruction ◽  
Bone Destruction ◽  
Microvascular Density ◽  
Blood Capillaries ◽  
Secondary Osteoarthritis ◽  
Femoral Heads ◽  
Formalin Fixed Paraffin Embedded ◽  
Destructive Arthropathy

Purpose. To assess the vascularity of the femoral head and determine how it is related to the destruction of the arthritic hip joint. The process of destructive arthropathy in arthritic hip joints is variable. Some patients with osteoarthritis of the hip have rapidly progressive destructive changes resulting in the disappearance of the femoral head. Method. Six femoral heads from patients diagnosed with rapidly destructive arthropathy and 6 femoral heads from patients with secondary osteoarthritis caused by acetabular dysplasia were analysed to reveal the association between blood capillaries and osteoclasts. The von Willebrand Factor immunostaining and counterstaining with Mayer's haematoxylin were used to label the microvessels and osteoclasts in formalin-fixed, paraffin-embedded specimens of femoral heads. The numbers of immunostained microvessels and osteoclasts in selected regions were counted. Result. The microvascular density of the bone surfaces of rapidly progressive arthritic hips was hypervascular. Osteoclasts were also found in increased numbers on the bone surfaces of rapidly progressive arthritic hips. The higher microvascular density coincided with extensive bone destruction and with the increased osteoclast count. Conclusion. These findings suggested that hypervascularity of the granulation in the femoral head may be associated with bone and joint destruction.

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