Medical Engineering & Physics 32 (2010) 1116–1123 Contents lists available at ScienceDirect Medical Engineering & Physics journal homepage: www.elsevier.com/locate/medengphy Recovery of bone strength in young pigs from an induced short-term dietary calcium deficit followed by a calcium replete diet Ameet K. Aiyangar a , Anthony G. Au a , Thomas D. Crenshaw b , Heidi-Lynn Ploeg a,∗ a Department of Mechanical Engineering, University of Wisconsin, Madison, United States b Department of Animal Science, University of Wisconsin, Madison, United States article info Article history: Received 7 October 2009 Received in revised form 30 July 2010 Accepted 7 August 2010 Keywords: Four-point bending Computed tomography Porcine femur Pre-pubertal Dietary calcium deficit abstract This study investigated whether the deficits in bone strength of pre-pubertal pigs, induced by short-term deficits in dietary calcium can be recovered if followed by a calcium-fortified diet. Young pigs were divided into two groups based on diet: a marginal Ca diet (70% of established Ca requirements) or an excess Ca diet (150% of established Ca requirements) for 4 weeks. Each group was then randomly sub-divided into two groups and fed diets with either marginal or excess dietary Ca for 6 weeks in a cross-over design, resulting in four treatment groups: H150–H150, H150–L70, L70–H150, and L70–L70. Animals were DXA scanned at 2-week intervals during the 10-week period to obtain whole body bone mineral content (BMC) and density (BMD). After animals were euthanized, right femurs were collected for this study. Traits such as bone mineral density, mass, volume, area moment of inertia (MI) and the section modulus (SM) were computed from computed tomography (CT) data and failure load was measured from four-point bending tests. DXA results showed significant reduction in BMC (61.6%) and BMD (37.5%) in the (L70–L70) group compared to the (H150–H150) group. DXA results additionally showed that deficiencies induced by the 4-week marginal Ca diet in the (L70–H150) group were not recovered with a subsequent excess Ca diet. While mechanical test results also showed significant reduction (75%) in strength in the L70–L70 group, compared to the H150–H150 group, they revealed no differences between the failure loads of the (L70–H150) group and the (H150–H150) group. Similar results were also found for bone mineral mass and volume, indicating that recovery from a short-term dietary Ca deficiency is possible at the pre- pubertal stage. Furthermore, bone mineral content and bone volume calculated from CT data correlated highly with failure load (R 2 = 0.78 and 0.84, respectively), while density, MI and SM only showed weak- to-moderate correlations (R 2 = 0.40–0.56), implying that bone mineral mass and volume calculated from CT data are good non-invasive surrogates for strength of growing bones. © 2010 IPEM. Published by Elsevier Ltd. All rights reserved. 1. Introduction Although osteoporosis is a serious and growing public health problem [1], comprehensive therapy for treating this disease remains elusive. Attainment of maximal peak bone mass at skele- tal maturation has been considered to be the best defense against subsequent debilitating age-related bone loss and fracture risk [2–5]. Dietary calcium (Ca) deficits during childhood may perma- nently reduce the genetically programmed maximal peak bone mass [2,6–10]. The potential to reverse the adverse effects of short- term calcium deficits in early growth phases on peak bone mass and bone strength by repletion with sufficient calcium intake in ∗ Corresponding author at: Department of Mechanical Engineering, University of Wisconsin, Madison, 1513 Engineering Drive, Madison, WI 53706, United States. Tel.: +1 6082622690. E-mail address: ploeg@engr.wisc.edu (H.-L. Ploeg). later growth phases is an important, but inadequately addressed question. Such a study, which, in humans, would require follow- ing subjects from early childhood to beyond peak bone mass to assess the influence of early calcium intake on lifetime fracture risk, is a difficult endeavor [11]. Successful execution of retro- spective or prospective observational studies in humans over long periods of time is limited by inaccuracies in dietary intake recall, i.e., inaccuracies of food questionnaires to identify calcium consumption [11] and low compliance rates [12]. Given the lim- itations involved in human trials, studies with animal models offer advantages in control of diet compliance and the length of time required to assess responses. Peterson et al. [17] used female rats, a commonly used animal model, to study the abil- ity of young bones to recover from the adverse effects of dietary calcium deficits. The deleterious effects of low calcium intake through adolescence in rats were non-reversible, resulting in a sub-optimal peak bone mass [17]. While this particular study did not investigate, separately, the effects in the pre-pubertal stage 1350-4533/$ – see front matter © 2010 IPEM. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.medengphy.2010.08.001