Ct-based finite element models can be used to estimate experimentally measured failure loads in the proximal femur

Koivumäki, Janne; Thevenot, Jérôme; Pulkkinen, Pasi; Kühn, Volker; Link, Thomas M.; Eckstein, F.; Jämsä, Timo

doi:10.1016/j.bone.2012.01.012

Cited by 116 publications

(75 citation statements)

References 40 publications

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“…were comparable to what models of intact human femurs in stance configuration achieve (R 2 = 0.82-0.95) [2,4,7,8,10,16]. QCT-based computer models were also able to catch the weakening of ovine femurs observed in vitro, even if the resection size had a larger influence on the FE predictions than it did experimentally.…”

Section: Discussionsupporting

confidence: 58%

“…Each scan was converted to BMD from the Hounsfield units (HU) through linear regressions established from our phantom's inserts (0, 100, 200, 400, 600, 800 mg HA/cm 3 ). While phantoms often feature a smaller number of low-density inserts (only up to 200 mg/ cc) [2,8], ours was custom-made to minimize the error in the linear HU/BMD relationship. To deal with multiple regions of interest (ROIs), ImageJ's ROI manager [23] (National Institutes of Health, Bethesda, MD, USA) was used.…”

Section: Methodsmentioning

confidence: 99%

“…Ideally, the resulting femoral strength after osteochondroplasty could be predicted preoperatively using computer simulations based on finite element (FE) methods. These computer models are generated from quantitative CT (QCT) after conversion of the Hounsfield units to bone mineral density (BMD) values [2,4,7,8,10,16] and provide an accurate measure of bone strength [31], a criterion that can discriminate patients at risk for hip fracture [6]. However, unlike numerous FE models predicting human femoral strength [2,4,7,8,10,16], the one study dealing with FAI correction [20] relied on a single femur with simplified linear elastic material properties (ie, no microcracks) and no direct experimental validation.…”

Section: Introductionmentioning

confidence: 99%

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Head-Neck Osteoplasty has Minor Effect on the Strength of an Ovine Cam-FAI Model: In Vitro and Finite Element Analyses

Maquer

Bürki

Nuss

et al. 2016

Clinical Orthopaedics &Amp; Related Research

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Background Osteochondroplasty of the head-neck region is performed on patients with cam femoroacetabular impingement (FAI) without fully understanding its repercussion on the integrity of the femur. Cam-type FAI can be surgically and reproducibly induced in the ovine femur, which makes it suitable for studying corrective surgery in a consistent way. Finite element models built on quantitative CT (QCT) are computer tools that can be used to predict femoral strength and evaluate the mechanical effect of surgical correction. Questions/purposes We asked: (1) What is the effect of a resection of the superolateral aspect of the ovine femoral head-neck junction on failure load? (2) How does the failure load after osteochondroplasty compare with reported forces from activities of daily living in sheep? (3) How do failure loads and failure locations from the computer simulations compare with the experiments? Methods Osteochondroplasties (3, 6, 9 mm) were performed on one side of 18 ovine femoral pairs with the contralateral intact side as a control. The 36 femurs were scanned via QCT from which specimen-specific computer models were built. Destructive compression tests then were conducted experimentally using a servohydraulic testing system and numerically via the computer models. Safety factors were calculated as the ratio of the maximal force measured in vivo by telemeterized hip implants during the sheep's walking and running activities to the failure load. The simulated failure loads and failure locations from the computer models were compared with the experimental results. Results Failure loads were reduced by 5% (95% CI, 2%-8%) for the 3-mm group (p = 0.0089), 10% (95% CI, 6%-14%) for the 6-mm group (p = 0.0015), and 19% (95% CI, 13%-26%) for the 9-mm group (p = 0.0097) compared with the controls. Yet, the weakest specimen still supported more than 2.4 times the peak load during running. Strong correspondence was found between the simulated and experimental failure loads (R 2 = 0.83; p \ 0.001) and failure locations. Conclusions The resistance of ovine femurs to fracture decreased with deeper resections. However, under in vitro testing conditions, the effect on femoral strength remains small even after 9 mm correction, suggesting that femoral

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Section: Discussionsupporting

confidence: 58%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Head-Neck Osteoplasty has Minor Effect on the Strength of an Ovine Cam-FAI Model: In Vitro and Finite Element Analyses

Maquer

Bürki

Nuss

et al. 2016

Clinical Orthopaedics &Amp; Related Research

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“…Although the prediction accuracy is considerably high both for strains (R 2 >0.95, (Schileo et al, 2008;Yosibash et al, 2007)) and femoral strength (standard error of estimation(SEE)<400 N, (Koivumäki et al, 2012)), FE models have not yet been introduced in clinical practice. This is due to several reasons including concerns about validation (Henninger et al, 2010;Viceconti et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

How accurately can subject-specific finite element models predict strains and strength of human femora? Investigation using full-field measurements

Grassi

Väänänen

Ristinmaa

et al. 2016

Journal of Biomechanics

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Subject-specific finite element models have been proposed as a tool to improve fracture risk assessment in individuals. A thorough laboratory validation against experimental data is required before introducing such models in clinical practice. Results from digital image correlation can provide full-field strain distribution over the specimen surface during in vitro test, instead of at a few pre-defined locations as with strain gauges. The aim of this study was to validate finite element models of human femora against experimental data from three cadaver femora, both in terms of femoral strength and of the full-field strain distribution collected with digital image correlation. The results showed a high accuracy between predicted and measured principal strains (R 2 =0.93, RMSE=10%, 1600 validated data points per specimen). Femoral strength was predicted using a rate dependent material model with specific strain limit values for yield and failure. This provided an accurate prediction (<2% error) for two out of three specimens.In the third specimen, an accidental change in the boundary conditions occurred during the experiment, which compromised the femoral strength validation. The achieved strain accuracy was comparable to that obtained in state-of-the-art studies which validated their prediction accuracy against 10-16 strain gauge measurements. Fracture force was accurately predicted, with the predicted failure location being very close to the experimental fracture rim. Despite the low sample size and the single loading condition tested, the present combined numerical-experimental method showed that finite element models can predict femoral strength by providing a thorough description of the local bone mechanical response.

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“…Several recent approaches have been developed to assign the anisotropic orientation of bone as a function of its cortical and trabecular structural morphology and mechanical behavior. These approaches include orientation methods using anatomical directions corresponding to the bone shape [7,26,38,90], variation in the CT Hounsfield unit values based on micromechanical considerations [30,66,73,76], bone remodeling simulation prior to fracture prediction to obtain the bone orthotropic orientation and elastic assignment [11,17,20,40,51], and a procedure to orientate orthotropic properties in a proximal femur FE model using the directions of the principal stresses produced by a physiological load scheme [64]. Empirical relations between the orthotropic constants and bone density have been suggested by several authors [29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

A quasi-brittle continuum damage finite element model of the human proximal femur based on element deletion

Hambli

2012

Med Biol Eng Comput

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Ct-based finite element models can be used to estimate experimentally measured failure loads in the proximal femur

Cited by 116 publications

References 40 publications

Head-Neck Osteoplasty has Minor Effect on the Strength of an Ovine Cam-FAI Model: In Vitro and Finite Element Analyses

Head-Neck Osteoplasty has Minor Effect on the Strength of an Ovine Cam-FAI Model: In Vitro and Finite Element Analyses

How accurately can subject-specific finite element models predict strains and strength of human femora? Investigation using full-field measurements

A quasi-brittle continuum damage finite element model of the human proximal femur based on element deletion

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