Effect of Tapered Geometry on the Load Transfer of an Idealized Cemented Hip Implant

2002 ◽  
Author(s):  
N. Nun˜o
Keyword(s):  
Residual Stresses ◽  
Bone Cement ◽  
Chemical Bond ◽  
Polymethyl Methacrylate ◽  
Load Transfer ◽  
Hip Implants ◽  
Cement Interface ◽  
Grouting Material ◽  
Surrounding Bone ◽  
Causes Of Failure

Implant looseining of cemented hip implants is one of the major causes of failure of the arthroplasty. In cemented hip implants, the polymethyl methacrylate (PMMA), also called bone cement, is used as grouting material between the stem and the surrounding bone. During polymerisation of the cement, residual stresses are generated in the bulk cement. The bone cement does not have a chemical bond with the stem nor the bone; however, it fills completely the space between the two and serves to distribute the load being transferred from the stem to the bone. Numerical analyses on the load transfer of cemented hip implants usually do not include the residual stresses due to cement curing at the stem-cement interface [1–2].

Effect of Tapered Geometry on the Load Transfer of an Idealized Cemented Hip Implant

2002 ◽  
Author(s):  
N. Nun˜o
Keyword(s):  
Residual Stresses ◽  
Bone Cement ◽  
Chemical Bond ◽  
Load Transfer ◽  
Hip Implants ◽  
Implant Loosening ◽  
Cement Interface ◽  
Grouting Material ◽  
Surrounding Bone ◽  
Causes Of Failure

Implant loosening of cemented hip implants is one of the major causes of failure of the arthroplasty. In cemented hip implants, the polymethyl methacrylate (PMMA), also called bone cement, is used as grouting material between the stem and the surrounding bone. During polymerisation of the cement, residual stresses are generated in the bulk cement. The bone cement does not have a chemical bond with the stem nor the bone; however, it fills completely the space between the two and serves to distribute the load being transferred from the stem to the bone. Numerical analyses on the load transfer of cemented hip implants usually do not include the residual stresses due to cement curing at the stem-cement interface [1–2].

Transient and Residual Stresses and Displacements in Self-Curing Bone Cement—Part II: Thermoelastic Analysis of the Stem Fixation System

1982 ◽  
Vol 104 (1) ◽  
pp. 28-37 ◽  
Author(s):  
A. M. Ahmed ◽  
R. Nair ◽  
D. L. Burke ◽  
J. Miller
Keyword(s):  
Adverse Effects ◽  
Residual Stresses ◽  
Bone Cement ◽  
Cancellous Bone ◽  
Thermal Stresses ◽  
Curing Process ◽  
Hardening Material ◽  
Cement Interface ◽  
Fixation System ◽  
Curing Cement

In this second part of a two-part report, an idealized model of the stem fixation system is analyzed to determine the adverse effects of the thermal stresses and displacements of bone cement during its curing process. The Shaffer-Levitsky stress-rate strain-rate law for chemically hardening material has been used. The results show that if the cement is surrounded by cancellous bone, as opposed to cortical bone, then transient tensile circumferential stresses in the cement and similar radial stresses at the stem/cement interface are generated. The former may cause flaws and voids within the still curing cement, while the latter may cause gaps at the interface.

MODELLING THE BONE-CEMENT INTERFACE IN CEMENTED HIP IMPLANTS

2008 ◽  
Vol 41 ◽  
pp. S68
Author(s):  
M.A. Pérez ◽  
J.M. García-Aznar ◽  
M. Doblaré
Keyword(s):  
Bone Cement ◽  
Hip Implants ◽  
Cement Interface

Bone-Cement Interface Micromechanical Model under Cyclic Loading

2011 ◽  
Vol 488-489 ◽  
pp. 391-394
Author(s):  
J.A. Sanz-Herrera ◽  
H. Esteban ◽  
M.P. Ariza
Keyword(s):  
Bone Cement ◽  
Hip Replacement ◽  
Mechanical Characterization ◽  
Micromechanical Model ◽  
Volume Element ◽  
Implant Loosening ◽  
Cement Interface ◽  
Causes Of Failure ◽  
Interface Geometry

Total hip replacement is one of the most common techniques in orthopaedic surgery, and one of the most important surgical advances of the last XX century. Normally, implant is fixed to bone by means of a polymer material known as bone cement, building an interface between implant and bone regions. Microscopically, two interfaces can be distinguished, namely, bone-cement and implant-cement interfaces. One of the main causes of failure is implant loosening due to fatigue of one of the two microscopic interfaces. In this work, a micromechanical analysis of bone-cement interface under cyclic forces is introduced. Both bone and cement are considered using different models based on fatigue damage over a statistically representative volume element (RVE) of the microstructure. This technique allows to homogenize mechanical stresses of the RVE yielding the effective macroscopic behavior of the bone-cement interface, avoiding experimental fitting case to case, once the interface geometry and mechanical characterization of the involved phases are known.

scholarly journals Damage of the Bone-Cement Interface in Finite Element Analyses of Cemented Orthopaedic Implants

2018 ◽  
Author(s):  
Toufik Bousnane ◽  
Smail Benbarek ◽  
Abderahmen Sahli ◽  
Boualem Serier ◽  
Bel Abbes Bachir Bouiadjra
Keyword(s):  
Bone Cement ◽  
Load Transfer ◽  
Cement Mantle ◽  
Damage Scenario ◽  
Cement Interface ◽  
Total Hip ◽  
Long Term Stability ◽  
Prosthetic Implants ◽  
Cement Penetration

In orthopedic surgery and particularly in total hip arthroplasty, fixation of femoral implant is generally made by the surgical cement. Bone–cement interface has long been implicated in failure of cemented total hip replacement (THA), it is actually a critical site that affect the long-term stability and survival of prosthetic implants after implantation. The main purpose of this study is to investigate the effect of cement penetration into the bone on damage scenario at the interface. Previously most researchers have been performed to study damage accumulation in the cement mantle for different amount of cement penetration. In this work, bone–cement interface integrity has been studied for different mechanical properties. Cohesive traction separation law is used to detect contact damage between cement and bone. Results showed that a larger debonded area was predicted proximally and distally. Adhesion between bone and cement is affected mainly by cement penetration into the bone. Higher cement penetration into the bone leads to a good load transfer. A lower strength of the bone–cement interface due to a lower mechanical property results in faster interface damage. So we advise surgeons to well perpetrate the bone for long-term durability of cemented THA.

Flow characteristics of curing polymethyl methacrylate bone cement

1998 ◽  
Vol 212 (3) ◽  
pp. 199-207 ◽  
Author(s):  
N J Dunne ◽  
J F Orr
Keyword(s):  
Shear Rate ◽  
Bone Cement ◽  
Polymethyl Methacrylate ◽  
Cancellous Bone ◽  
Power Index ◽  
Flow Characteristics ◽  
Flow Index ◽  
Shear Stresses ◽  
Bone Cements ◽  
Cement Interface

During polymerization, polymethyl methacrylate bone cements have complex viscoelastic characteristics. Within a short working time they transform from dough-like consistencies to solid cements. Therefore, the time at which a cement is introduced to cancellous bone surfaces and subjected to pressure is important, to achieve optimum flow and mechanical interdigitation. Achieving adequate mechanical interlock increases the area for load transfer and reduces localized bone-cement interface stresses. The aim of this study was to measure the flow characteristics for commercial bone cements as a function of time and calculate the apparent viscosities for the curing bone cements The capillary extrusion method was used to measure the rate of flow of the curing cement, by means of a melt flow index apparatus, which was manufactured in-house. The tests were conducted using nozzles of different lengths and under two loads. This enabled the power index value, n, and the pressure at the die entry, Po, to be calculated for each material with respect to time. Once the flow characteristics were determined, a series of formulae were used to calculate the shear rates, y, the shear stresses, r, and the apparent viscosities, na, of the curing bone cements. The results indicated that acrylic bone cements are non-Newtonian, pseudoplastic materials, since the power index values are less than 1.0 during the curing stage. The consistency indices, K, were calculated from the shear stress versus shear rate data. The apparent viscosities of the cements were found to increase with respect to increases in time. Clinically, it was considered desirable to inject and pressurize the cement into the medullary canal while its viscosity is relatively low in order to obtain maximum interdigitation into cancellous bone, provided adequate containment and a means of pressurization can be achieved. The pseudoplastic character of bone cements is responsible for their reduction in viscosity with increased shear rate, a property that may be exploited to enhance penetration with appropriate delivery.

scholarly journals Computational Study on Interfacial Interactions between Polymethyl Methacrylate-Based Bone Cement and Hydroxyapatite in Nanoscale

2021 ◽  
Vol 11 (7) ◽  
pp. 2937
Author(s):  
Hongdeok Kim ◽  
Byeonghwa Goh ◽  
Sol Lee ◽  
Kyujo Lee ◽  
Joonmyung Choi
Keyword(s):  
Bone Cement ◽  
Polymethyl Methacrylate ◽  
Load Transfer ◽  
Computational Study ◽  
Thermomechanical Properties ◽  
External Loading ◽  
Crosslinking Reaction ◽  
Mechanical Stiffness ◽  
Joint Replacement Surgery ◽  
Pull Out

Polymethyl methacrylate (PMMA)-based bone cement (BC) is a key material in joint replacement surgery that transfers external forces from the implant to the bone while allowing their robust binding. To quantitatively evaluate the effect of polymerization on the thermomechanical properties of the BC and on the interaction characteristics with the bone ceramic hydroxyapatite (HAp), molecular dynamics simulations were performed. The mechanical stiffness of the BC material under external loading increased gradually with the crosslinking reaction occurrence, indicating increasing load transfer between the constituent molecules. In addition, as the individual Methyl Methacrylate (MMA) segments were interconnected in the system, the freedom of the molecular network was largely suppressed, resulting in more thermally stable structures. Furthermore, the pull-out tests using HAp/BC bilayer models under different constraints (BC at 40% and 85%) revealed the cohesive characteristics of the BC with the bone scaffold in molecular detail. The stiffness and the fracture energy increased by 32% and 98%, respectively, with the crosslink density increasing.

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