TECHNICAL ARTICLE A Portable Small-Scale Mechanical Loading and Testing Device: Validation and Application to a Mouse Tibia Loading Model V.A. Bhatia 1 and K.L. Troy 1,2 1 Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60612, USA 2 Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA Keywords Test Methods, Biomechanics, Validation, In Vivo Loading, Material Testing Correspondence K.L. Troy, Department of Kinesiology & Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA Email: klreed@uic.edu Received: November 10, 2011; accepted: May 31, 2012 doi:10.1111/j.1747-1567.2012.00843.x Abstract A small scale mechanical loading and testing device was designed and fabricated to apply in vivo loads to mouse tibiae and to mechanically test the bones in three-point bending. A linear actuator and load cell were used to apply accurately controlled forces to the samples. The device was tested and validated using standard materials of known properties to quantify accuracy and precision. The device had accuracy and precision errors of less than 5% for most of the material tests, an accuracy error of less than 10% and precision error of less than 5% for in vivo loading, and a precision error of less than 5% for ex vivo bone testing. Our results showed that the device was capable of implementing loading interventions and could be used as a tool to assess the response of these interventions. This device represents one solution to the lack of portability and a high setup cost that prevent some research groups from adopting in vivo animal loading. Introduction The mechanical properties of bones have been mea- sured and studied with the goal of understanding the influence of mechanical loading environment on biological processes that affect bone structure and quality. The mouse tibia 1,2 and rat ulna 3,4 load- ing models are well suited to address mechanobi- ological questions. These models require application of controlled in vivo loads, and often, quantification of mechanically important outcomes. In small rodents, this necessitates a small-scale and high resolution mechanical testing set-up. Some commercially available mechanical testing devices are partially portable and have the necessary specifications for in vivo loading and testing small sized samples. These are often used with additional modifications and attachments for applying in vivo loads in small rodent models. However, these devices often have a substantial setup cost. Lack of portability and a high setup cost present a barrier to some research groups that might otherwise adopt in vivo animal loading. Fritton et al. 1 used a non-commercial device for a mouse tibial loading model, but did not describe the device in detail. Webster et al. 5 developed a custom setup to load mouse tail vertebrae, whereas, Leppanen et al., 6 Peng et al., 7 and Jamsa et al. 8 used setups for three-point mechanical testing of rodent long bones. To our knowledge, there are no portable designs that have the versatility to apply in vivo loads and to test the mechanical properties of the bone. Therefore, our purposes were (1) to design and fabricate a portable low cost mechanical load- ing and testing device to apply in vivo loads to mouse tibiae and, for mechanical testing of mouse tibiae, (2) to create and tune the control system for accurate in vivo loading of a mouse tibia, (3) to val- idate the device using standard materials, (4) and to use the device on mice. Methods Device specifications The device was designed with the goal of measuring mechanical stiffness values with less than 5% error, having a precision error of less than 5%, and applying in vivo loads within 10% of a specified target value. A Experimental Techniques (2012) © 2012, Society for Experimental Mechanics 1