Chen, X.

Clifford, L.

Kish, Vincent

Noble, G.

Norman, Timothy L.

Pechey, C.

Porter, D. S.

Yener, Y. N.

English

Digital Commons

Cedarville UniversityDigitalCommons@CedarvilleEngineering and Computer Science FacultyPresentations School of Engineering and Computer Science3-2-2008Fracture Toughness is More Sensitive to BoneRemodeling Parameters than Strength andToughnessTimothy L. NormanCedarville University, tnorman@cedarville.eduX. ChenG. NobleD. S. PorterVincent KishSee next page for additional authorsFollow this and additional works at: http://digitalcommons.cedarville.edu/engineering_and_computer_science_presentationsPart of the Biomedical Engineering and Bioengineering CommonsThis Poster Session is brought to you for free and open access byDigitalCommons@Cedarville, a service of the Centennial Library. It hasbeen accepted for inclusion in Engineering and Computer Science FacultyPresentations by an authorized administrator ofDigitalCommons@Cedarville. For more information, please contactdigitalcommons@cedarville.edu.Recommended CitationNorman, Timothy L.; Chen, X.; Noble, G.; Porter, D. S.; Kish, Vincent; Pechey, C.; Clifford, L.; and Yener, Y. N., "Fracture Toughnessis More Sensitive to Bone Remodeling Parameters than Strength and Toughness" (2008). Engineering and Computer Science FacultyPresentations. 101.http://digitalcommons.cedarville.edu/engineering_and_computer_science_presentations/101AuthorsTimothy L. Norman, X. Chen, G. Noble, D. S. Porter, Vincent Kish, C. Pechey, L. Clifford, and Y. N. YenerThis poster session is available at DigitalCommons@Cedarville: http://digitalcommons.cedarville.edu/engineering_and_computer_science_presentations/101Poster No. 925 • 54th Annual Meeting of the Orthopaedic Research SocietyFracture Toughness is More Sensitive to Bone Remodeling Parameters than Strength and ToughnessTimothy L. Norman1,2, Xidong Chen1, Garrett Noble1, Dan Porter2, Vince Kish2, Carola Pechey3, Clifford Les3, Yener Yeni31Engineering and Computer Science, Cedarville University, Cedarville, OH; 2Orthopaedics, West Virginia University, Morgantown, WV; 3Boneand Joint Center, Henry Ford Hospital, Detriot, MItnorman@cedarville.eduIntroduction: Common mechanical measures of bone quality include bonestrength, fracture toughness and material toughness. Fracture toughness calculatedfrom linear elastic fracture mechanics refers to the fairly localized energy requiredto cause macrocrack initiation or propagation [1]. Material toughness (work tofracture) is an extrinsic property, calculated from the area of the load-displacementcurve and represents the energy absorbed prior to the generation of microcracksplus the energy required to start and drive the final macrocracks in order to breakthe material [2]. Both fracture and material toughness are frequently used indescribing material quality however their sensitivity to bone remodeling parame-ters has not been compared. It was hypothesized that intrinsic material properties,i.e. strength and fracture toughness, are more reflective of bone remodeling param-eters than are extrinsic material properties, e.g. work to fracture. The objective ofthis research was to investigate and compare the relationships between the com-mon bone mechanical measures and the microstructural and compositional vari-ables associated with bone remodeling and micro- and diffuse damage.Materials and Methods: Twenty-two femoral midshafts from 12 female and 10males ranging in age from 26 years to 92 years (average age = 62.5 ± 20.0 years)were used in this study. Mode I and Mode II compact tension and shear fracturetoughness specimens were machined from the femurs and tested [3]. Mode I (GI)and mode II (GII) fracture toughness (strain energy release rates) were determinedusing linear elastic fracture mechanics. In addition, two longitudinally orientedthree-point-bend specimens (30mm X 4mm X 2mm) were also removed from eachfemoral midshaft by a diamond wire saw [4]. Bending properties (ultimate load atfailure, Pult, and work to fracture or area under the load-displacement curve, WAUC)were determined by loading each specimen until failure on a three-point-bendloading configuration with unsupported span of 15 mm on roller edges. The load-ing rate was 5mm/min on a MTS machine model 812.21 (MTS SystemsCorporations, MN). The ultimate load at failure was the maximum load achievedduring the loading cycle and the work to fracture was found from the area underthe load-displacement curve (Fig. 1). After testing, thin sections were obtainedfrom each specimen, polished and stained with hemotoxylin-eosin for morpholog-ical evaluation [5]. Compositional variables were also obtained from remainingbone [3]. Diffuse and microscopic damage were also measured from stained bulksections obtained from the midshafts [6]. Microstructural and compositional vari-ables were correlated to the mechanical measurements using simple regressionanalysis. The statistical package JMPTM (SAS institute, Cary, NC) was used in thestatistical analysis. Significance was set at p<0.05.Fig. 1 Load-displacement test for calculating toughness (WAUC) and failure load (Pult) underthree-pt-bend.Results: GI and GII fracture toughness significantly correlated with six vari-ables and ultimate load at failure significantly correlated with three variables andmarginally (p<0.096) correlated with a fourth variable (Table 1). The work to frac-ture, WAUC, was not significantly related to remodeling associated parameters butdid significantly correlate with diffuse damage density.Table 1. Correlations between microstructural and compositional remodeling variables, dam-age and mechanical measurements (p (R)).Discussion: Strength and fracture toughness are calculated to include maxi-mum loads that are defined by the onset of failure or macroscopic cracking.According to these results, these intrinsic properties are more directly influenced bymicrostructural and compositional changes that occur with Haversian remodelingand bone damage than are the extrinsic property work-to-fracture. Therefore,strength and fracture toughness may be indicators that are more sensitive to boneadaptation than work to fracture. Based on the number of significant correlations,it may be concluded that fracture toughness is more sensitive to remodeling param-eters compared to strength measures. It is also interesting to note that of all thevariables investigated, work to fracture significantly correlated to ultrastructuraldamage only. Previous reports have found that the collagen network plays animportant role in the toughness of bone [7], however collagen was not measured inthis study. Based on the findings of this study, it is also concluded that bone tough-ness is independent of remodeling parameters but is significantly altered by ultra-structural damage.References: 1. Anderson, T.L., Fracture Mechanics, CRC Press, AnnArbor, 1991.2. Zioupos, P. and Currey, J.D., Bone, Vol. 22, No. 1, pp. 57-66, 1998.3. Yeni et al., Bone, Vol. 22. No. 1, pp. 79-84, 1998.4. Wang, X., Bone, Vol. 31, pp. 1-7, 2002.5. Yeni et al., Bone, Vol. 21, No. 5, pp. 453-459, 1997.6. Norman, T.L. and Little, 53rd Annual Meeting, Orthopaedic ResearchSociety, Feb. 11-14, 2007, No. 262.7. Wang X et al., J. Orthop. Res., 19(6), pp. 1021-6, 2001.Acknowledgements: The authors would like to thank Suzanne Smith,Department of Orthopaedics at West Virginia University, for histological prepara-tions.

Fracture Toughness is More Sensitive to Bone Remodeling Parameters than Strength and Toughness

https://digitalcommons.cedarville.edu/cgi/viewcontent.cgi?article=1100&context=engineering_and_computer_science_presentations

Fracture Toughness is More Sensitive to Bone Remodeling Parameters than Strength and Toughness

Abstract

Similar works

Full text

Available Versions

Digital Commons