scholarly journals Study of Contact Pressures in Total Hip Replacement

2020 ◽  
Author(s):  
Myron Czerniec ◽  
Jarosław Zubrzycki
Keyword(s):  
Contact Pressure ◽  
Hip Joint ◽  
Correct Selection ◽  
Radial Clearance ◽  
Total Hip ◽  
Metal Head ◽  
Hip Joint Endoprosthesis ◽  
Joint Load ◽  
The Impact ◽  
Maximum Contact

Total hip arthroplasty is a complex procedure. The achievements of implantology enabled the development of a faithful representation of hip joint physiology as well as the production of materials that can successfully replace damaged natural tissues. A very important issue is the correct selection of the geometry of the endoprosthesis adequate to the load of the joint. Materials used for endoprosthesis are a metal head and a polymer cup (e.g. PE-UHMW). The main interactions in the endoprosthesis are friction and surface pressure, which must be limited, exceeding them causes the destruction of the biomechanical system - plastic deformation of the polymer and the formation of too large and unacceptable radial clearances. Based on the author's developed calculation method of hip joint endoprosthesis contact parameters, the impact on maximum contact pressure and the angle of contact of the joint load was estimated depending on the diameter of the endoprosthesis and radial clearance. The correctness of changing the values of maximum contact pressure from the mentioned parameters was determined. Correspondingly: an increase in joint load causes a linear increase in the maximum contact pressure; increasing the diameter of the endoprosthesis head - their non-linear decrease, and increasing radial clearance - their increase

ANALYSIS OF CONTACT PRESSURE BETWEEN THE PARTS OF TOTAL HIP JOINT ENDOPROSTHESIS WITH SHAPE DEVIATIONS

2007 ◽  
Vol 40 ◽  
pp. S558 ◽  
Author(s):  
V. Fuis ◽  
T. Návrat ◽  
P. Hlavon ◽  
M. Koukal ◽  
M. Houfek
Keyword(s):  
Contact Pressure ◽  
Hip Joint ◽  
Total Hip ◽  
Shape Deviations ◽  
Hip Joint Endoprosthesis

scholarly journals Evaluating the Impact and Norming the Parameters of Partially Regular Texture on the Surface of the Articulating Ball Head in a Total Hip Joint Prosthesis

2016 ◽  
Vol 11 (4) ◽  
pp. 527-539 ◽  
Author(s):  
Vladimir Pakhaliuk ◽  
Alexander Polyakov ◽  
Mikhail Kalinin ◽  
Sergey Bratan
Keyword(s):  
Hip Joint ◽  
Joint Prosthesis ◽  
Total Hip ◽  
The Impact ◽  
Regular Texture

Analysis of contact mechanics in McKee-Farrar metal-on-metal hip implants

2003 ◽  
Vol 217 (5) ◽  
pp. 333-340 ◽  
Author(s):  
A Yew ◽  
M Jagatia ◽  
H Ensaff ◽  
Z M Jin
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Contact Region ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Contact Pressure Distribution ◽  
Acetabular Cup ◽  
Metal On Metal ◽  
Half Angle ◽  
Maximum Contact

Contact mechanics analysis for a typical McKee-Farrar metal-on-metal hip implant was carried out in this study. The finite element method was used to predict the contact area and the contact pressure distribution at the bearing surfaces. The study investigated the effects of the cement and underlying bone, the geometrical parameters such as the radial clearance between the acetabular cup and the femoral head, and the acetabular cup thickness, as well as other geometrical features on the acetabular cup such as lip and studs. For all the cases considered, the predicted contact pressure distribution was found to be significantly different from that based upon the classical Hertz contact theory, with the maximum value being away from the centre of the contact region. The lip on the cup was found to have a negligible effect on the predicted contact pressure distribution. The presence of the studs on the outside of the cup caused a significant increase in the local contact pressure distribution, and a slight decrease in the contact region. Reasonably good agreement of the predicted contact pressure distribution was found between a three-dimensional anatomical model and a simple two-dimensional axisymmetric model. The interfacial boundary condition between the acetabular cup and the underlying cement, modelled as perfectly fixed or perfectly unbonded, had a negligible effect on the predicted contact parameters. For a given radial clearance of 0.079 mm, the decrease in the thickness of the acetabular cup from 4.5 to 1.5 mm resulted in an increase in the contact half angle from 15° to 26°, and a decrease in the maximum contact pressure from 55 to 20 MPa. For a given acetabular cup thickness of 1.5 mm, a decrease in the radial clearance from 0.158 to 0.0395mm led to an increase in the contact half-angle from 20° to 30°, and a decrease in the maximum contact pressure from 30 to 10 MPa. For zero clearance, although the contact pressure was significantly reduced over most of the contact area, the whole acetabular cup came into contact with the femoral head, leading to stress concentration at the edge of the cup. Design optimization of the geometrical parameters, in terms of the acetabular cup thickness and the radial clearance, is important, not only to minimize the contact stress at the bearing surfaces, but also to avoid equatorial and edge contact.

Effect of Head Surface Roughness and Sterilization Method on Wear of UHMWPE Acetabular Cups: Preliminary Hip Joint Simulator Results

2006 ◽  
Author(s):  
Anneli Jedenmalm ◽  
Walther Leardini ◽  
Mara Zavalloni ◽  
Saverio Affatato
Keyword(s):  
Surface Roughness ◽  
Hip Joint ◽  
Calf Serum ◽  
The Body ◽  
Acetabular Cup ◽  
Sterilization Method ◽  
Metal Head ◽  
Head Surface ◽  
The Impact ◽  
Hip Joint Simulator

More than one million hip joint replacements are performed each year in the world. However, the implants do not last forever due to material limitations, even though the operation is successful. The most common material combination used today is a CoCr head articulating against an UHMWPE (Ultra High Molecular Weight Polyethylene) acetabular cup. Several investigations have shown that the metal head is roughened inside the body and thus accelerating wear of the polymer cup. The sterilization method is also known to have effect on the wear properties. In vitro wear tests are however usually performed with as new implants. This investigation aimed at study the impact of head surface roughness on wear of both sterilized and non-sterilized acetabular cups. A total of nine acetabular cup and head pairs were wear tested in a hip joint simulator for 2Million cycles (Mc) with bovine calf serum as lubricant. Wear was determined by weighing of all cups. The heads were of CoCrMo and the average initial head surface roughness was 15nm (Ra), measured with a white light interference profilometer. The roughening was produced with a SiC paper producing circular multidirectional wear tracks to a surface roughness of about 400nm (Ra). The cups were of UHMWPE and the sterilized cups were 3Mrad gamma-radiated in nitrogen. The surface roughness after wear test was unchanged for the roughened heads, while the initially smooth heads were slightly roughened. Preliminary results show that the rough heads increase the wear of the cups 2-fold. The γ-irradiation affected both wear- and soak rate.

Stress Analysis of the Hip Joint Endoprosthesis Ceramic Head for Different Values of Shape Deviations

2014 ◽  
Vol 936 ◽  
pp. 770-775 ◽  
Author(s):  
Vladimír Fuis ◽  
Premysl Janicek
Keyword(s):  
Tensile Stress ◽  
Hip Joint ◽  
Computational Modelling ◽  
Ceramic Head ◽  
Weakest Link ◽  
Shape Deviations ◽  
Hip Joint Endoprosthesis ◽  
Link Theory ◽  
Conical Surfaces ◽  
The Impact

The paper deals with the problems of ceramic head of hip joint endoprosthesis destructions, and with assessing the impact of shape deviations of conical surfaces on the tensile stress under ISO 7206-5 loading. The failure of the hip joint endoprosthesis ceramic head has always traumatic consequences for the patient, since a part of or even the whole endoprosthesis has to be reoperated. Hence, it is desired to reduce the number of implant re-operations to the minimum. Therefore the computational modelling of the stress of the head was realised. The shape deviations of the ideal contact cone areas of the head and stem are parameters that significantly influence the tensile stress in the head and its reliability. The assumed shape deviations of the head’s and stem’s cones are macro shape deviations (different cone taper) and micro shape deviations (unevennes) measured using the IMS-UMPIRE equipment. The stress state in the ceramic heads was solved using the FEM and head’s failure probability is based on the Weibull weakest link theory [4, 5 and 9].

scholarly journals The local concentration of Ca2+ correlates with BMP7 expression and osseointegration in patients with total hip arthroplasty

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaodong Fu ◽  
Weili Wang ◽  
Xiaomiao Li ◽  
Yingjian Gao ◽  
Hao Li ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Femoral Head ◽  
Total Hip Arthroplasty ◽  
Hip Joint ◽  
Hip Arthroplasty ◽  
Local Concentration ◽  
Gruen Zone ◽  
Osteoclast Activity ◽  
Total Hip ◽  
The Impact

Abstract Background A successful osseointegration of total hip arthroplasty (THA) relies on the interplay of implant surface and bone marrow microenvironment. This study was undertaken to investigate the impact of perioperative biochemical molecules (Ca2+, Mg2+, Zn2+, VD, PTH) on the bone marrow osteogenetic factors (BMP2, BMP7, Stro-1+ cells) in the metaphyseal region of the femoral head, and further on the bone mineral density (BMD) of Gruen R3. Methods Bone marrow aspirates were obtained from the discarded metaphysis region of the femoral head in 51 patients with THA. Flow cytometry was used to measure the Stro-1+ expressing cells. ELISA was used to measure the concentrations of bone morphologic proteins (BMP2 and BMP7) and the content of TRACP5b in serum. TRAP staining was used to detect the osteoclast activity in the hip joint. The perioperative concentrations of the biochemical molecules above were measured by radioimmunoassay. The BMD of Gruen zone R3 was examined at 6 months after THA, using dual-energy X-ray absorptiometry (DEXA). Results Our data demonstrated that the concentration of Ca2+ was positively correlated with BMP7 expression, and with the postoperative BMD of Gruen zone R3. However, the concentration of Mg2+ had little impact on the R3 BMD, although it was negatively correlated with the expression of BMP7. Osteoclast activity in hip joint tissue of patients with femoral neck fractures was increased. Compared with the patients before THA, the levels of TRACP5b in serum of patients after THA were decreased. The data also suggested that the other biochemical molecules, such as Zn2+, VD, and PTH, were not significantly correlated with any bone marrow osteogenetic factors (BMP2, BMP7, Stro-1+ cells). The postoperative R3 BMD of patients of different gender and age had no significant difference. Conclusions These results indicate the local concentration of Ca2+ may be an indicator for the prognosis of THA patients.

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