Deformation pattern and load transfer of an uncemented femoral stem with modular necks. An experimental study in human cadaver femurs

Enoksen, Cathrine H.; Gjerdet, Nils Roar; Klaksvik, Jomar; Arthursson, Astvaldur J.; Schnell-Husby, Otto; Wik, Tina Strømdal

doi:10.1016/j.clinbiomech.2016.01.001

Cited by 10 publications

(4 citation statements)

References 94 publications

(105 reference statements)

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“…The influence of the offset variant used on load transmission in the proximal femur represents another essential aspect. A biomechanical comparison of different offset variants of a modular conventional straight stem demonstrated only minor changes on overall femoral load transmission [ 10 ], whereas varus implant positioning resulted in a significant increase in the distal load transfer [ 15 ]. Relevant changes in the proximal third of the implant, particularly in the calcar region, were not found in this biomechanical investigation.…”

Section: Discussionmentioning

confidence: 99%

Biomechanics of a calcar loading and a shortened tapered femoral stem: Comparative in-vitro testing of primary stability and strain distribution

Freitag¹,

Bieger²,

Kiefer³

et al. 2021

J EXP ORTOP

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Purpose The most common femoral short stems available on the market can, in principle, be divided with regard to their anchoring concepts into a calcar loading and a shortened tapered design. The purpose of this study was to compare the primary stability and stress-shielding of two short stems, which correspond to these two different anchoring concepts. Methods Using seven paired fresh frozen human cadaver femurs, primary axial and rotational stabilities under dynamic load (100–1600 N) were evaluated by miniature displacement transducers after 100,000 load cycles. Changes in cortical strains were measured before and after implantation of both stem types to detect implant-specific load transmission and possible stress-shielding effects. Results Reversible and irreversible micromotions under dynamic load displayed no significant differences between the two implants. Implantation of either stem types resulted in a reduction of cortical strains in the proximal femur, which was less pronounced for the calcar loading implant. Conclusions Both short stems displayed comparable micromotions far below the critical threshold above which osseointegration may disturbed. Neither short stem could avoid proximal stress-shielding. This effect was less pronounced for the calcar loading short stem, which corresponds to a more physiological load transmission.

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Section: Discussionmentioning

confidence: 99%

Biomechanics of a calcar loading and a shortened tapered femoral stem: Comparative in-vitro testing of primary stability and strain distribution

Freitag¹,

Bieger²,

Kiefer³

et al. 2021

J EXP ORTOP

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show abstract

“…28,29 Several stem designs have been developed in human medicine to improve proximal fixation and minimize complications. 23,30 Other factors have received great attention, especially related to implant rigidity (materials with different elasticity modules), stem length and location of the porous area. Usually, the design aims to allow for a load transfer from the femoral stem to the bone in a way that is as similar as possible to the physiological transfer, minimizing the decrease in mechanical stimulus.…”

Section: Discussionmentioning

confidence: 99%

Photoelastic Analysis of Two Different Cementless Femoral Stems for Total Hip Arthroplasty in a Canine Model

et al. 2019

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Objectives The aim of this article was to analyse and compare internal stress generated at different points of a femoral photoelastic model after insertion and axial load application using two different cementless femoral stems for total hip arthroplasty in dogs: a collared stem combined with limited textured surface and absence of grooves and a collarless stem with fully textured surface and grooves. Methods Ten femoral photoelastic models, divided into two groups, were created using two different designs of cementless femoral stems. The models were submitted to axial loading on the femoral head in a universal test machine. The internal stress (kPa) around the femoral stems was evaluated at seven predetermined points using a transmission polariscope. Results The internal stress at the femoral calcar was larger in the models with collared stem combined with limited textured surface and absence of grooves (p < 0.05). No differences were identified between the groups in the other points (p > 0.05), corresponding to the tip of the stems and proximal lateral region of the femur. Conclusions The collar of femoral stem combined with the absence of grooves and more limited textured surface increase the axial load transmission to the femoral calcar, and in vivo, it may act to reduce complications, such as subsidence and stress shielding. However, other biomechanical tests and clinical evaluations must be performed to determine other important aspects for the implantation of these prostheses.

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“…The microstructure associated with porous features, such as vascular channels, may have contributed influences to the stress concentrations and stress shielding around implants, yet the importance of these channels in the mechanical behaviour of cortical bone is not well understood. The design and integration of an implant and understanding of the bone‐prosthesis interface are important factors in prosthetic design, but the interaction between prosthesis and cortical bone at a fundamental microstructural level is relatively poorly understood . It is proposed that if one can characterize how the heterogeneity in the microstructure affects the macroscale stress, particularly periprosthetically, this may herald a greater potential for innovative, longer lasting prostheses designs.…”

Section: Introductionmentioning

confidence: 99%

A numerical investigation and experimental verification of size effects in loaded bovine cortical bone

Frame

Wheel

Riches

2017

Numer Methods Biomed Eng

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In this paper, we present 2-and 3-dimensional finite element-based numerical models of loaded bovine cortical bone that explicitly incorporate the dominant microstructural feature: the vascular channel or Haversian canal system. The finite element models along with the representation of the microstructure within them are relatively simple: 2-dimensional models, consisting of a structured mesh of linear elastic planar elements punctuated by a periodic distribution of circular voids, are used to represent beam samples of cortical bone in which the channels are orientated perpendicular to the sample major axis, while 3-dimensional models, using a corresponding mesh of equivalent solid elements, represent those samples in which the canals are aligned with the axis. However, these models are exploited in an entirely novel approach involving the representation of material samples of different sizes and surface morphology. The numerical results obtained for the virtual material samples when loaded in bending indicate that they exhibit size effects not forecast by either classical (Cauchy) or more generalized elasticity theories. However, these effects are qualitatively consistent with those that we observed in a series of carefully conducted experiments involving the flexural testing of bone samples of different sizes. Encouraged by this qualitative agreement, we have identified appropriate model parameters, primarily void volume fraction but also void separation and matrix modulus by matching the computed size effects to those we observed experimentally. Interestingly, the parameter choices that provide the most suitable match of these effects broadly concur with those we actually observed in cortical bone.KEYWORDS cortical bone, finite element analysis, generalized continuum, mechanical behaviour, micropolar (Cosserat) elasticity, size effect

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Deformation pattern and load transfer of an uncemented femoral stem with modular necks. An experimental study in human cadaver femurs

Abstract: The small differences of strain between the modular necks tested in this study are not expected to influence bone remodeling in the proximal femur.

Cited by 10 publications

References 94 publications

Biomechanics of a calcar loading and a shortened tapered femoral stem: Comparative in-vitro testing of primary stability and strain distribution

Biomechanics of a calcar loading and a shortened tapered femoral stem: Comparative in-vitro testing of primary stability and strain distribution

Photoelastic Analysis of Two Different Cementless Femoral Stems for Total Hip Arthroplasty in a Canine Model

A numerical investigation and experimental verification of size effects in loaded bovine cortical bone

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