Medical Engineering & Physics 36 (2014) 774–778 Contents lists available at ScienceDirect Medical Engineering & Physics jo ur nal home p ag e: www.elsevier.com/locate/medengphy Technical note Comparison of in vitro techniques to controllably decrease bone mineral density of cancellous bone for biomechanical compressive testing Francesca R. Nichols a , Kent N. Bachus a,b,c,∗ a Orthopaedic Research Laboratory, University of Utah Orthopaedic Center, 590 Wakara Way, Suite A100, Salt Lake City, UT 84108, USA b Bone and Joint Research Laboratory, George E. Wahlen Department of Veterans Affairs, Medical Center, Salt Lake City, UT 84148, USA c Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA a r t i c l e i n f o Article history: Received 10 January 2013 Received in revised form 7 January 2014 Accepted 5 February 2014 Keywords: Bone mineral density Compressive strength Demineralization pDEXA a b s t r a c t It is not surprising that an orthopedic device used with poorly mineralized bone can have lower mechani- cal fixation strength than the same device with well-mineralized bone. As new devices are being designed and tested, it is important to develop a controllable technique to decrease the bone mineral density of bone in vitro, so the fixation strength of the devices can be better modeled. Several different bone dem- ineralization techniques have been established, but some use caustic chemicals and comparisons of their rates of demineralization have not been performed. In this study, a total of 120 cancellous bone cores were excised from ovine vertebra, scanned using a pico dual energy X-ray absorptiometry system to determine bone mineral density, then placed into one of five solutions (0.9% saline, 0.5 M hydrochloric acid, 0.5 M ethylenediaminetetraacetic acid, 0.5 M formic acid, and 5% acetic acid). For each solution, 12 time periods ranging from 0 to 144 h were investigated. After demineralization, all cores were rescanned and biomechanically loaded in compression to failure. Based on the rate of demineralization, the ease of use, the availability, and the correlation with the compressive bone strength, it was determined that the 5% acetic acid was the optimal demineralization solution to controllably decrease the bone mineral density of cancellous bone. © 2014 IPEM. Published by Elsevier Ltd. All rights reserved. 1. Introduction Independent of whether it is primary osteoporosis resulting from menopause or advanced age, or whether it is secondary osteo- porosis resulting from disease or certain medications [1,2], the World Health Organization asserts that osteoporosis ranks second only to cardiovascular disease as a leading health care problem [3], affecting nearly 44 million people in the United States alone [4]. It is projected that of Americans over the age of 50 years, about 50% of all women and 25% of all men will suffer from fractures of osteoporotic bone [4], commonly within the femoral neck, spine, and wrist [5]. These osteoporotic bone fractures, known as fragility fractures [6], are caused by decreased bone mineral density (BMD) Abbreviations: BMD, bone mineral density; pDEXA, pico dual energy X-ray absorptiometry; HCl, hydrochloric acid; EDTA, ethylenediaminetetraacetic acid; FA, formic acid. ∗ Corresponding author at: Orthopaedic Research Laboratory, University of Utah Orthopaedic Center, 590 Wakara Way, Suite A100, Salt Lake City, UT 84108, USA. Tel.: +1 801 587 5200; fax: +1 801 587 5211. E-mail address: kent.bachus@hsc.utah.edu (K.N. Bachus). within the bone tissues, which includes a decrease in the tissue mineral density and a concomitant decrease in the trabecular mor- phology, thickness, and number, resulting in a weakening of the bone. Clinical treatments of most bone fractures include some sort of device to help stabilize the fracture site until the bone heals. For example, bone plates and screws are used to stabilize the spine after a vertebral fracture [7]. Furthermore, a patient with a fractured femoral neck may require a total hip replacement to stabilize the joint [8]. These types of orthopedic constructs tend to work well in good quality bone, but in patients with decreased BMD, these devices may not be completely effective. In attempts to develop alternate fixation strategies for these patients, investigators have utilized various bone models to exam- ine the success of orthopedic devices under decreased BMD conditions. When living tissues are required, investigators often use animal models treated with a combination of ovariectomy, cal- cium and vitamin D restricted diet, and steroid treatments [9,10]. Live animal models, however, are typically used to test various drug treatments, but are usually cost prohibitive for the purposes of biomechanical studies. http://dx.doi.org/10.1016/j.medengphy.2014.02.003 1350-4533/© 2014 IPEM. Published by Elsevier Ltd. All rights reserved.