Application of Multi Criteria Optimization Method in Implant Design to Reduce Stress Shielding

The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve implant fixation.

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Long-term bone remodelling around ‘legendary’ cementless femoral stems

EFORT Open Reviews ◽

10.1302/2058-5241.3.170024 ◽

2018 ◽

Vol 3 (2) ◽

pp. 45-57 ◽

Cited By ~ 16

Author(s):

Charles Rivière ◽

Guido Grappiolo ◽

Charles A. Engh ◽

Jean-Pierre Vidalain ◽

Antonia-F. Chen ◽

...

Keyword(s):

Bone Loss ◽

Bone Remodelling ◽

Bone Ingrowth ◽

Stress Shielding ◽

Implant Design ◽

Periprosthetic Bone ◽

Femoral Stems ◽

Periprosthetic Bone Loss ◽

Load Pattern

Bone remodelling around a stem is an unavoidable long-term physiological process highly related to implant design. For some predisposed patients, it can lead to periprosthetic bone loss secondary to severe stress-shielding, which is thought to be detrimental by contributing to late loosening, late periprosthetic fracture, and thus rendering revision surgery more complicated. However, these concerns remain theoretical, since late loosening has yet to be documented among bone ingrowth cementless stems demonstrating periprosthetic bone loss associated with stress-shielding. Because none of the stems replicate the physiological load pattern on the proximal femur, each stem design is associated with a specific load pattern leading to specific adaptive periprosthetic bone remodelling. In their daily practice, orthopaedic surgeons need to differentiate physiological long-term bone remodelling patterns from pathological conditions such as loosening, sepsis or osteolysis. To aid in that process, we decided to clarify the behaviour of the five most used femoral stems. In order to provide translational knowledge, we decided to gather the designers’ and experts’ knowledge and experience related to the design rationale and the long-term bone remodelling of the following femoral stems we deemed ‘legendary’ and still commonly used: Corail (Depuy); Taperloc (Biomet); AML (Depuy); Alloclassic (Zimmer); and CLS-Spotorno (Zimmer).Cite this article: EFORT Open Rev 2018;3:45-57. DOI: 10.1302/2058-5241.3.170024

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A validated finite element study of stress shielding in a novel hybrid knee implant

10.32920/ryerson.14649990.v1 ◽

2021 ◽

Author(s):

Ziauddin Mahboob

Keyword(s):

Experimental Study ◽

Finite Element ◽

Finite Element Model ◽

Bone Tissue ◽

Stress Shielding ◽

Stress Transfer ◽

Element Model ◽

Implant Design ◽

Polyamide 12 ◽

Compressive Loads

This study (1) proposes a hybrid knee implant design to improve stress transfer to bone tissue in the distal femur by modifying a conventional femoral implant to include a layer of carbon fibre reinforced polyamide 12, and (2) develops a finite element model of the prosthetic knee joint, validated by comparison with a parallel experimental study. The Duracon knee system was used in the experimental study, and its geometry was modelled using CAD software. Synthetic bone replicas were used instead of cadaveric specimens in the experiments. The strains generated on the femur and implant surfaces were measured under axial compressive loads of 2000 N and 3000 N. A mesh of 105795 nodes was needed to obtain sufficient accuracy in the finite element model, which reproduced the experimental reading within 10-23% in six of the eight test locations. The model of the proposed hybrid design showed considerable improvements in stress transfer to the bone tissue at three test flexion angles of 0°, 20°, and 60°.

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Minimizing Stress Shielding and Cement Damage in Cemented Femoral Component of a Hip Prosthesis through Computational Design Optimization

Advances in Orthopedics ◽

10.1155/2017/8437956 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

Abdellah Ait Moussa ◽

Justin Fischer ◽

Rohan Yadav ◽

Morshed Khandaker

Keyword(s):

Hip Prosthesis ◽

Numerical Technique ◽

Stress Shielding ◽

Computational Design ◽

Functionally Graded ◽

Implant Design ◽

Homogeneous Material ◽

Element Analysis ◽

Term Survival

The average life expectancy of many people undergoing total hip replacement (THR) exceeds twenty-five years and the demand for implants that increase the load-bearing capability of the bone without affecting the short- or long-term stability of the prosthesis is high. Mechanical failure owing to cement damage and stress shielding of the bone are the main factors affecting the long-term survival of cemented hip prostheses and implant design must realistically adjust to balance between these two conflicting effects. In the following analysis we introduce a novel methodology to achieve this objective, the numerical technique combines automatic and realistic modeling of the implant and embedding medium, and finite element analysis to assess the levels of stress shielding and cement damage and, finally, global optimization, using orthogonal arrays and probabilistic restarts, were used. Applications to implants, fabricated using a homogeneous material and a functionally graded material, were presented.

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Optimization of custom cementless stem using finite element analysis and elastic modulus distribution for reducing stress-shielding effect

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/0954411916686125 ◽

2017 ◽

Vol 231 (2) ◽

pp. 149-159 ◽

Cited By ~ 10

Author(s):

Gurunathan Saravana Kumar ◽

Subin Philip George

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Elastic Modulus ◽

Stress Shielding ◽

Von Mises Stress ◽

Shielding Effect ◽

Implant Design ◽

Element Analysis ◽

Von Mises ◽

Reducing Stress

This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress–strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.

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Mathematical Optimization of Elastic Properties: Application to Cementless Hip Stem Design

Journal of Biomechanical Engineering ◽

10.1115/1.2796076 ◽

1997 ◽

Vol 119 (2) ◽

pp. 166-174 ◽

Cited By ~ 49

Author(s):

J. H. Kuiper ◽

R. Huiskes

Keyword(s):

Bone Loss ◽

Design Optimization ◽

Elastic Properties ◽

Stress Shielding ◽

Proximal Part ◽

Optimization Method ◽

Arbitrary Distribution ◽

Interface Failure ◽

Stem Design ◽

Finite Element Program

The designer of a cementless hip stem in total hip replacement must find a balance between two conflicting demands. On the one hand, a stiff stem shields the surrounding bone from mechanical loading (stress shielding), which may lead to bone loss, particularly around the proximal part of the stem. Reducing the stem stiffness decreases the amount of stress shielding and hence the amount of bone loss. However, this measure inevitably promotes higher proximal interface stresses and thereby increases the risk of proximal interface failure. The designer’s task therefore is to optimize the stem stiffness in order to find the best compromise in the conflict. Yet, a better compromise might be found when the stem material was nonhomogeneous, in other words when an arbitrary distribution of the elastic properties inside the stem was allowed. The number of conceivable designs would increase enormously, making the designer’s task almost impossible. In the present paper, we develop a numerical design optimization method to determine the optimal stiffness characteristics for a hip stem. A finite element program is coupled with a numerical optimization method, thus producing a design optimization scheme. The scheme minimizes the probability for interface failure while limiting the amount of bone loss, by adapting the parameters describing the nonhomogeneous elastic modulus distribution. As an example, a simplified model of a hip stem is made, whose modulus distribution is optimized. Assuming equal long-term bone loss, the maximum interface stress can be reduced by over 50 percent when compared to a homogeneous flexible stem, thus demonstrating the value of the new approach.

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Stress shielding following stemless anatomic total shoulder arthroplasty

Shoulder & Elbow ◽

10.1177/17585732211058804 ◽

2021 ◽

pp. 175857322110588

Author(s):

William R Aibinder ◽

Fares Uddin ◽

Ryan T Bicknell ◽

Ryan Krupp ◽

Markus Scheibel ◽

...

Keyword(s):

Shoulder Arthroplasty ◽

Functional Outcomes ◽

Total Shoulder Arthroplasty ◽

Case Series ◽

Stress Shielding ◽

Implant Design ◽

Level Of Evidence ◽

Lesser Tuberosity ◽

Significant Difference

Background Finite element analysis has suggested that stemless implants may theoretically decrease stress shielding. The purpose of this study was to assess the radiographic proximal humeral bone adaptations seen following stemless anatomic total shoulder arthroplasty. Methods A retrospective review of 152 prospectively followed stemless total shoulder arthroplasty utilizing a single implant design was performed. Anteroposterior and lateral radiographs were reviewed at standard time points. Stress shielding was graded as mild, moderate, and severe. The effect of stress shielding on clinical and functional outcomes was assessed. Also, the influence of subscapularis management on the occurrence of stress shielding was determined. Results At 2 years postoperatively, stress shielding was noted in 61 (41%) shoulders. A total of 11 (7%) shoulders demonstrated severe stress shielding with 6 occurring along the medial calcar. There was one instance of greater tuberosity resorption. At the final follow-up, no humeral implants were radiographically loose or migrated. There was no statistically significant difference in clinical and functional outcomes between shoulders with and without stress shielding. Patients undergoing a lesser tuberosity osteotomy had lower rates of stress shielding, which was statistically significant ( p = 0.021) Discussion Stress shielding does occur at higher rates than anticipated following stemless total shoulder arthroplasty, but was not associated with implant migration or failure at 2 years follow-up. Level of evidence IV, Case series.

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A validated finite element study of stress shielding in a novel hybrid knee implant

10.32920/ryerson.14649990 ◽

2021 ◽

Author(s):

Ziauddin Mahboob

Keyword(s):

Experimental Study ◽

Finite Element ◽

Finite Element Model ◽

Bone Tissue ◽

Stress Shielding ◽

Stress Transfer ◽

Element Model ◽

Implant Design ◽

Polyamide 12 ◽

Compressive Loads

This study (1) proposes a hybrid knee implant design to improve stress transfer to bone tissue in the distal femur by modifying a conventional femoral implant to include a layer of carbon fibre reinforced polyamide 12, and (2) develops a finite element model of the prosthetic knee joint, validated by comparison with a parallel experimental study. The Duracon knee system was used in the experimental study, and its geometry was modelled using CAD software. Synthetic bone replicas were used instead of cadaveric specimens in the experiments. The strains generated on the femur and implant surfaces were measured under axial compressive loads of 2000 N and 3000 N. A mesh of 105795 nodes was needed to obtain sufficient accuracy in the finite element model, which reproduced the experimental reading within 10-23% in six of the eight test locations. The model of the proposed hybrid design showed considerable improvements in stress transfer to the bone tissue at three test flexion angles of 0°, 20°, and 60°.

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Transitional Stiffness Intramedullary Stems to Reduce Periprosthetic Pain

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-175997 ◽

2007 ◽

Author(s):

R. D. Crowninshield ◽

D. Wentz ◽

W. Paprosky ◽

A. Rosenberg ◽

A. Stoller

Keyword(s):

Load Transfer ◽

Stress Shielding ◽

Implant Design ◽

Transitional Region ◽

Interface Pressure ◽

Bone Stress ◽

Intramedullary Canal ◽

Prosthetic Component ◽

Distribution Of Stress ◽

Surrounding Bone

The intramedullary canal presence of a stemmed prosthetic component can be expected to change the distribution of stress from the joint loading to the adjacent skeleton. The reconstructed skeletal stiffening that results for relatively rigid prosthetic components can result in periprosthetic stress shielding. The abrupt change in reconstruction stiffness that can occur at the implant stem terminus can be associated with periprosthetic pain. A stem end “clothes pin” slot, intended to make a stem end more flexible, produces a substantially asymmetric and abrupt alteration of stem stiffness. The present work is directed to analyzing ways that the structural stiffness of the terminus region of a prosthetic stem can be controlled to provide a symmetrical transitional region of controllable load transfer to the surrounding bone. It is hypothesized that through implant design, prosthesis-to-bone interface pressure and periprosthetic bone stress levels at a prosthetic stem terminus can be reduced and that this will be associated with a reduced occurrence and severity of “end of stem pain” in a variety of prosthetic applications.

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Topology Optimisation for Compliant Hip Implant Design and Reduced Strain Shielding

Materials ◽

10.3390/ma14237184 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7184

Author(s):

Nathanael Tan ◽

Richard van Arkel

Keyword(s):

Load Transfer ◽

Stress Shielding ◽

Implant Design ◽

Topology Optimisation ◽

Hip Implant ◽

Implant Survivorship ◽

Hip Stems ◽

Bone Structures ◽

Optimisation Techniques ◽

Strain Shielding

Stiff total hip arthroplasty implants can lead to strain shielding, bone loss and complex revision surgery. The aim of this study was to develop topology optimisation techniques for more compliant hip implant design. The Solid Isotropic Material with Penalisation (SIMP) method was adapted, and two hip stems were designed and additive manufactured: (1) a stem based on a stochastic porous structure, and (2) a selectively hollowed approach. Finite element analyses and experimental measurements were conducted to measure stem stiffness and predict the reduction in stress shielding. The selectively hollowed implant increased peri-implanted femur surface strains by up to 25 percentage points compared to a solid implant without compromising predicted strength. Despite the stark differences in design, the experimentally measured stiffness results were near identical for the two optimised stems, with 39% and 40% reductions in the equivalent stiffness for the porous and selectively hollowed implants, respectively, compared to the solid implant. The selectively hollowed implant’s internal structure had a striking resemblance to the trabecular bone structures found in the femur, hinting at intrinsic congruency between nature’s design process and topology optimisation. The developed topology optimisation process enables compliant hip implant design for more natural load transfer, reduced strain shielding and improved implant survivorship.

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