Medical Engineering & Physics 31 (2009) 1228–1234 Contents lists available at ScienceDirect Medical Engineering & Physics journal homepage: www.elsevier.com/locate/medengphy A study on the mechanical properties of beagle femoral head using the digital speckle correlation method Qinghua Wang a , Huimin Xie a,∗ , Peifu Tang b , Qi Yao c , Peng Huang b , Pengwan Chen d , Fenglei Huang d a AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China b Orthopedic, 301 Chinese PLA General Hospital, Beijing 100853, China c Orthopedic, Beijing Shijitan Hospital, Beijing 100038, China d State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China article info Article history: Received 4 January 2009 Received in revised form 24 July 2009 Accepted 29 July 2009 Keywords: Femoral head Deformation DSCM Young’s modulus Poisson’s ratio abstract The mechanical properties of the femoral head are known to play an important role in the athletic per- formance of animals. In this paper, the full-field displacement and strain distributions of beagle femoral head samples in the U and V fields under loading were measured using the digital speckle correlation method (DSCM), and some deformation characteristics were analyzed. Young’s modulus and Poisson’s ratio were calculated to demonstrate the notable axial anisotropy of the femoral head. The axial compres- sive Young’s modulus varies from 361 MPa to 583 MPa, and the transverse one is 213 MPa. The Poisson’s ratio in the axial–transverse direction ranges from 0.14 to 0.29, and the one in the transverse–axial direction is 0.07. Experimental results validated the accuracy of this measurement, providing a potential reference for investigating the deformation performance of the femoral head. © 2009 IPEM. Published by Elsevier Ltd. All rights reserved. 1. Introduction With more and more people afflicted with necrosis of the femoral head, the development of artificial femoral heads attracts greater attention. The head of the femur has the capacity of rebuild- ing, a phenomenon of functional adaptation, endowed by the unique configuration of the trabecular bone. The micro-structure of the trabecular bone affects its mechanical properties, such as strength and stiffness, which directly decide the magnitude of the strain, and finally the process of functional adaptation [1,2]. Struc- ture bionics [3,4] is stimulating scientists’ interest owing to its wide applications in biology, medicine, military, aerospace, and other fields, and imitation of the femoral head as a virtual tool to design and develop new smart structures draws great attention as well. Subsequently, evaluating the mechanical properties of the femoral head to design artificial and smart structures becomes a focal researching point. However, much work on the femoral head concentrates on finite element analysis and numerical simulation [5,6]. Few studies have determined the mechanical properties and loading behaviors of the femoral head from experimental aspects, so little knowledge is known about these to date. Although a testing machine enables us to obtain the force– displacement curves and thus the Young’s moduli of the tested ∗ Corresponding author. Tel.: +86 10 62792286; fax: +86 10 62781824. E-mail address: xiehm@mail.tsinghua.edu.cn (H. Xie). samples, local micro-scale variations are necessarily ignored. A full- field optical technique, electronic speckle pattern interferometry (ESPI) [7,8], has been proposed to determine the full-field defor- mation of materials under loading. The accuracy of deformation measurement is greatly improved using this technique, but the experimental set-up and procedure are very complicated and limit its application. In addition, this technique requires a very strictly controlled experimental environment such as vibration isolation, and fringe processing is also a challenging and difficult issue. Micro- and nano-indentation have been reported to measure the Young’s constants of the cortical bone at the micro-structural level [9,10]. However, micro- and nano-indentation are irrelevant for deter- mining the overall Young’s modulus of the cancellous bone, as the region of interest (ROI) is too small [11,12]. Fortunately, the digital speckle correlation method (DSCM), originally advocated in 1982 [13], has been developed into an effective and popular optical tech- nique that allows the full-field estimation of displacements and strains on a surface under loading [14–16]. Recently, DSCM has shown its merits in the deformation measurement of materials: it is full-field, non-contact, sensitive to illumination and vibration, and has a simple optical set-up and preparation of the samples and test environment requirements. Its wide range of success- ful applications in scientific research and engineering, including biomechanics [17–20], has clearly demonstrated its versatility and effectiveness. This study aims to measure the full-field distribution of defor- mation, the Young’s modulus, as well as the Poisson’s ratio of the 1350-4533/$ – see front matter © 2009 IPEM. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.medengphy.2009.07.021