Incorporation Of Interference Fit And Cyclic Loading In Simulation Algorithm For Better Prediction Of Micromotion Of Femoral Stems

2012 ◽  
Author(s):  
Mohammed Rafiq Abdul–Kadir ◽  
Ulrich N. Hansen
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Hip Arthroplasty ◽  
Bone Ingrowth ◽  
Fibrous Tissue ◽  
Interference Fit ◽  
Press Fit ◽  
Key Words Hip ◽  
Femoral Stems

Pelonggaran aseptik adalah salah satu daripada sebab utama pembedahan ulangan tulang paha. Ini berlaku disebabkan kegagalan untuk mendapatkan cengkaman pertama yang kuat. Pergerakan antara implan dengan tulang melebihi had tertentu menghalang pertumbuhan tulang dan mengakibatkan pembentukan tisu berbentuk fiber. Dalam kajian ini, satu algoritma dicadangkan untuk meramal pergerakan implan dan seterusnya ketidakstabilan implan. Dengan menggunakan beban fisiologi, pergerakan implan relatif kepada tulang dikira menggunakan algoritma. Implan yang menggunakan sistem cengkaman tekanan telah dibentuk dan beban ulangan dikenakan untuk memberi simulasi yang sebenar. Satu ujikaji ‘in–vitro’ telah dilaksanakan terhadap empat tulang paha manusia untuk mengesahkan algoritma yang dicadangkan. Keputusan ujikaji telah mengesahkan pergerakan implan yang dijangka oleh algoritma ini. Kata kunci: tulang paha, algoritma cengkaman, pengesahan ujikaji Aseptic loosening is one of the major causes for revision surgery in hip arthroplasty. This has been attributed to failure in achieving strong primary fixation. Interface micromotion beyond a certain threshold limit inhibits bone ingrowth and favours the formation of fibrous tissue. In this study, an algorithm was constructed to predict micromotion and therefore instability of femoral stems. Based on common physiological loading, micromotion is calculated throughout the bone–implant interface. Press fit stem insertion was modelled using interference fit and cyclic loading was used to better simulate actual loading configuration. An in–vitro micromotion experiment was carried out on four human cadaveric femurs to validate the micromotion algorithm. A good correlation was obtained between finite element predictions and the in–vitro micromotion experiment. Key words: hip arthroplasty, primary stability, micromotion algorithm, experimental validation, finite element

scholarly journals Global fit concept in revision hip arthroplasty for cementless press-fit femoral stems

2017 ◽  
Vol 103 (4) ◽  
pp. 579-581 ◽  
Author(s):  
F. Canovas ◽  
P. LeBeguec ◽  
J. Batard ◽  
F. Gaillard ◽  
L. Dagneaux
Keyword(s):  
Hip Arthroplasty ◽  
Revision Hip Arthroplasty ◽  
Press Fit ◽  
Femoral Stems ◽  
Global Fit

Enhancement of initial stability of press-fit femoral stems using injectable calcium phosphate cement: an in vitro study in dog bones

Biomaterials ◽  
2004 ◽  
Vol 25 (17) ◽  
pp. 3887-3894 ◽  
Author(s):  
E.M. Ooms ◽  
N. Verdonschot ◽  
J.G.C. Wolke ◽  
W.Van de Wijdeven ◽  
M.M.M. Willems ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Calcium Phosphate Cement ◽  
In Vitro Study ◽  
Vitro Study ◽  
Press Fit ◽  
Initial Stability ◽  
Femoral Stems

Experimental and Finite Element Investigation of Cementless Cup/Bone Interface After Total Hip Arthroplasty

2004 ◽  
Author(s):  
Ivan Zivkovic ◽  
Farid Amirouche ◽  
Francisco Romero ◽  
Mark Gonzalez
Keyword(s):  
Finite Element ◽  
Total Hip Arthroplasty ◽  
Hip Arthroplasty ◽  
Bone Ingrowth ◽  
Element Model ◽  
Loading Conditions ◽  
Acetabular Cup ◽  
Bone Interface ◽  
Total Hip ◽  
Cementless Cup

Permanent fixation of a cementless total hip arthroplasty requires bone ingrowth into the femoral and acetabular components. Early micromotion at the acetabular cup/bone interface can preclude ingrowth threatening long term fixation. To better characterize micromotion of the interface under loading conditions, an experimental and finite element (FE) study was undertaken. In this study cadaver hemi-pelvises were implanted with cementless acetabular cups and subjected to cyclical axial load and torque. Detailed finite element model, validated with experimental results, was developed to further analyze the conditions affecting the initial stability and loosening of the interface for different loading conditions.

Thorn Implant: A Novel Mechanism for Interamedullary Stem Fixation

2002 ◽  
Author(s):  
M. Kasra ◽  
M. D. Grynpass
Keyword(s):  
Bone Formation ◽  
Vascular System ◽  
Bone Ingrowth ◽  
Fixation Method ◽  
Close Apposition ◽  
Interference Fit ◽  
Bone Implant ◽  
Press Fit ◽  
Initial Stability ◽  
Coated Implant

Existing non-cemented prostheses fixation mechanisms use press-fit techniques to obtain initial stability between bone and implant. For example, the primary fixation of non-cemented total hip stem prosthesis is achieved by carefully impacting the implant to the broached, contoured proximal femur. A successful primary fixation will be followed by the secondary fixation caused by bone ingrowth into the porous surface of implant. However, the primary postoperative fixation of the implants is usually far from ideal [1, 2]. Theoretically, for bone ingrowth to occur, a porous coated implant must be rigidly fixed with close apposition to the bone, without causing excessive stresses and stains at the bone-implant interface. However, this would require the medullar cavity to be prepared to very tight tolerances. In practice, this press fit technique requires interference fit between the prosthesis and the bone, thus creating large stresses and strains. In this case severe impacts for fitting the prosthesis may also fracture the bone. Therefore, it is important that the broaching and contouring of the femur be carried out carefully and exactly. This results in operations being lengthier and more complex. Furthermore, reaming and broaching damage bone vascular system delaying bone formation. The objective of this study was to introduce a novel fixation method, which can achieve immediate initial stability at the operation without having the mentioned problems of contemporary prosthetic designs. In this method, instead of waiting for the bone ingrowth to occur, pins from the inside of a hollow prosthesis stem are driven into the bone making a thorn implant. Therefore, fixation is achieved by so-called metal ingrowth into the bone instead of bone ingrowth into metal.

scholarly journals Finite Element Analysis of Uncemented Total Hip Replacement: the Effect of Bone-Implant Interface

2018 ◽  
Vol 7 (4.26) ◽  
pp. 230 ◽  
Author(s):  
Nur Faiqa Ismail ◽  
Solehuddin Shuib ◽  
Muhd Azman Yahaya ◽  
Ahmad Zafir Romli ◽  
Amran Ahmed Shokri
Keyword(s):  
Finite Element ◽  
Coefficient Of Friction ◽  
Implant Design ◽  
Implant Loosening ◽  
Interference Fit ◽  
Bone Implant ◽  
Hip Implant ◽  
Total Hip ◽  
Finite Element Software ◽  
Press Fit

Most uncemented total hip replacements (THR) rely on press-fit for the initial stability and thus lead to the secondary fixation which is biological fixation. Choosing the accurate interference fit may have a great effect on implant stability and implant loosening prevention. Implant loosening is the most reported problem where it leads the increasing of micromotion at the bone-implant interface due to insufficient primary fixation. By having sufficient stability or fixation after surgery, minimal relative motion between the prosthesis and bone interfaces allows osseointegration to occur. Therefore, it will provide a strong prosthesis-to-bone biological attachment. The aim of this study was to evaluate the effect of bone-implant interface for uncemented hip implant. In this study, a three-dimensional model of hip implant was designed and analysed by using commercial Finite Element Software namely, ANSYS WORKBENCH V15 software in order to investigate the bone-implant interface effect using the chosen implant design. The value of interference fit (δ= 0.01, 0.05, 0.10 and 0.50 mm) and coefficient of friction (δ= 0.15, 0.40 and 1.00) were used to simulate the bone-implant interface. It was found that the interference fit of 0.50 mm was sufficient to achieve the primary fixation and also the best fitting; thus, the implant loosening can be minimized. The interference fit of 0.50 mm was the minimal value to achieve fixation, while the coefficient of friction did not affect the bone-implant interface. 

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