Evaluation of Cement Stresses in Finite Element Analyses of Cemented Orthopaedic Implants

2001 ◽  
Vol 123 (6) ◽  
pp. 623-628 ◽  
Author(s):  
A. B. Lennon ◽  
P. J. Prendergast
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Load Transfer ◽  
Hip Prosthesis ◽  
Peak Stress ◽  
Longitudinal Direction ◽  
Orthopaedic Implants ◽  
Element Analysis ◽  
Stressed Volume ◽  
Tensile Stresses

Stress analysis of the cement fixation of orthopaedic implants to bone is frequently carried out using finite element analysis. However, the stress distribution in the cement layer is usually intricate, and it is difficult to report it in a way that facilitates comparison of implants for pre-clinical testing. To study this problem, and make recommendations for stress reporting, a finite element analysis of a hip prosthesis implanted into a synthetic composite femur is developed. Three cases are analyzed: a fully bonded implant, a debonded implant, and a debonded implant where the cement is removed distal to the stem tip. In addition to peak stresses, and contour and vector plots, a stressed volume and probability-of-failure analysis is reported. It is predicted that the peak stress is highest for the debonded stem, and that removal of the distal cement more than halves this peak stress. This would suggest that omission of the distal cement is good for polished prostheses (as practiced for the Exeter design). However, if the percentage of cement stressed above a certain threshold (say 3 MPa) is considered, then the removal of distal cement is shown to be disadvantageous because a higher volume of cement is stressed to above the threshold. Vector plots clearly demonstrate the different load transfer for bonded and debonded prostheses: A bonded stem generates maximum tensile stresses in the longitudinal direction, whereas a debonded stem generates most tensile stresses in the hoop direction, except near the tip where tensile longitudinal stresses occur due to subsidence of the stem. Removal of the cement distal to the tip allows greater subsidence but alleviates these large stresses at the tip, albeit at the expense of increased hoop stresses throughout the mantle. It is concluded that a thorough analysis of cemented implants should not report peak stress, which can be misleading, but rather stressed volume, and that vector plots should be reported if a precise analysis of the load transfer mechanism is required.

scholarly journals Finite Element analysis of stress state in the cement of total hip prosthesis with elastomeric stress barrier

2021 ◽  
Vol 15 (57) ◽  
pp. 281-290
Author(s):  
Allaoua Fadela ◽  
Lebbal Habib ◽  
Belarbi Abderrahmane
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Femoral Head ◽  
Load Transfer ◽  
Hip Prosthesis ◽  
Total Hip Prosthesis ◽  
Element Analysis ◽  
Acceptable Solution ◽  
Total Hip

In the total hip prosthesis, according to different positions of the patient, there are a variety of loads acting on femoral head which generate stress concentration in the cement called polymethylmethacrylat (PMMA) and consequently in the interfaces stem/cement/bone. This load transfer can provoke loosening of the implant from the femoral bone. This paper focused on optimal stress distribution in the total hip prosthesis and devoted to the development of a redesigned prosthesis type in order to minimize stress concentration in the cement. This study investigated the effect of elastomeric stress barrier incorporated between the stem and femoral head using 3D-finite element analysis. This proposed implant provoked lower load transfer in the cement due to the elastomeric effect as stress absorber.  However, the proposed model provided an acceptable solution for load transfer reduction to the cement. This investigation permitted to increase the service life of the total hip prosthesis avoiding the loosening.

scholarly journals Full Contoured Tooth-Implant Supported 3-Pointic All-Ceramic Denture During Occlusal Load Transfer in Lateral Region

2016 ◽  
Vol 61 (2) ◽  
pp. 843-846 ◽  
Author(s):  
J. Żmudzki ◽  
P. Malara ◽  
G. Chladek
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bone Tissue ◽  
Load Transfer ◽  
Element Analysis ◽  
Lateral Region ◽  
The Finite Element Analysis ◽  
All Ceramic ◽  
Dental Professional ◽  
Wide Zone

Abstract Implant and a tooth supported dentures are avoided by dentists because of uneven distribution of occlusal loads between a stiffer implant and a more pliable tooth. The hypothesis was that a 3-point all-ceramic bridge supported on a natural second premolar tooth and a two-pieces typical implant bears safely mastication loads. The finite element analysis showed that the implant splinted by all-ceramic zirconium bridge with the second premolar was safe under lateral mastication load, but there was found an overload at wide zone of bone tissue around the implant under the load of 800 N. The patients can safely masticate, but comminution of hard food should be avoided and they should be instructed that after such an indiscretion they need to contact a dental professional, because, in spite of integrity of the prosthesis, the bone tissue around the implant may fail and there is a hazard of intrusion of the tooth.

Finite element analysis of bone and implant stresses for customized 3D-printed orthopaedic implants in fracture fixation

2020 ◽  
Vol 58 (5) ◽  
pp. 921-931 ◽  
Author(s):  
Lina Yan ◽  
Joel Louis Lim ◽  
Jun Wei Lee ◽  
Clement Shi Hao Tia ◽  
Gavin Kane O’Neill ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fracture Fixation ◽  
Orthopaedic Implants ◽  
Element Analysis ◽  
3D Printed

Key Parameters Evaluation for Hip Prosthesis with Finite Element Analysis

2007 ◽  
Author(s):  
Hongqiang Guo ◽  
Dichen Li ◽  
Qin Lian ◽  
Xiang Li ◽  
Zhongmin Jin ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Hip Prosthesis ◽  
Element Analysis

ACETABULAR LOAD-TRANSFER AND MECHANICAL STABILITY: A FINITE ELEMENT ANALYSIS COMPARING DIFFERENT CEMENTLESS SOCKETS

2014 ◽  
Vol 14 (05) ◽  
pp. 1450063 ◽  
Author(s):  
D. F. M. PAKVIS ◽  
D. JANSSEN ◽  
B. W. SCHREURS ◽  
N. VERDONSCHOT
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Load Transfer ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Stress Shielding ◽  
Physiological Strain ◽  
Element Analysis ◽  
Strain Pattern ◽  
Component Interface

Acetabular stress shielding may be a failure mechanism of acetabular constructs promoting osteolysis, aseptic loosening and failure. We used three-dimensional finite element analysis (FEA) to evaluate the effect of flexible sockets on acetabular stress shielding. The sockets were made of (1) full polyethylene (PE), (2) PE with a metal bearing and (3) a PE insert with a metal backing was used as a traditional stiff implant. We compared the strain energy density and interfacial micro-motions between bone and cementless sockets during walking. In our FEA model, the most elastic socket (case 1) showed the highest levels of micro-motion during walking (400 μm). The most rigid socket (case 3) showed smaller areas of high micro-motions. Assuming a threshold for ingrowth of 50 microns, the flexible cup showed an ingrowth area of almost 40%, whereas the other two cases showed stable areas covering 60% of the total bone–component interface. Furthermore, we found that the introduction of an implant generates a very different strain pattern directly around the implant as compared with the intact case, which has a horse-shoe shaped cartilage layer in the acetabulum. This difference was not affected much by the stiffness of the implant; a more flexible implant resulted in only slightly higher strain levels. Bone strains over 1.5 mm from the cup showed physiological values and were not affected by the stiffness of the implant. Hence, this study shows that the physiological strain patterns are not obtained in the direct periprosthetic bone, regardless of the stiffness of the material.

Preliminary Evaluation of a New Dental Implant Design with Finite Element Analysis

2005 ◽  
Vol 288-289 ◽  
pp. 657-660
Author(s):  
Xue Jun Wang ◽  
R. Wang ◽  
J.M. Luo ◽  
Ji Yong Chen ◽  
Xing Dong Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dental Implant ◽  
Peak Stress ◽  
Implant Design ◽  
Preliminary Evaluation ◽  
Element Analysis ◽  
Mechanical Coupling ◽  
Stress Transmission ◽  
Reducing Stress

It is important to obtain mechanical coupling between dental implants and bone, because the lack of mechanical coupling may cause bone loss around implants. In this research, a new cylindrical dental implant composed of three parts was designed to offer favored mechanical environment for the bone. A special gap structure changed the means of the stress transmission and decreased the stress in the cortical bone around the neck of the implant. Through finite element analysis (FEA) of stress distribution in bone around implant-bone interface, the advantages of this new implant (reducing stress concentration in cervical cortex and satisfying varieties of clinical needs) were verified. The peak stress for the new design was about 30 percent less than that of the traditional implant and the flexibility of the design was also confirmed by changing the gap depth and the wall thickness.

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