Relationship between bone strength and dual-energy X-ray absorptiometry measurements in a screening protocol for pigs

¹ The Royal Veterinary and Agricultural University, 32 Dyrlaegevej, DK-1870 Frederiksberg C., Denmark
² The National Committee for Pig Production, 3 Axeltorv, DK-1609 Copenhagen, Denmark
³ Hvidovre University Hospital, 30 Kettegaard Alle, DK-2650 Hvidovre, Denmark

^* To whom correspondence should be addressed. E-mail: dhn{at}kvl.dk.

	Abstract

Computed tomography (CT) and a three point bending test, were performed on the metacarpal bones of adult production pigs to test the hypothesis that bone strength is strongly correlated with areal bone mineral density (BMD) in this population. The aim of the study was to subject material from adult production pigs grouped by bone mineral density to three-point bending, to test this hypothesis and determine the strength of any correlation. In all, 168 individual CT scans and mechanical tests were performed on the collected material. For evaluation purposes the material was divided into the categories, low, medium and high BMD (less than 1, 1 to 1.4 and greater than 1.4 g/cm², respectively). The results show a difference in maximum load, in stress at maximum load and stiffness between each BMD group (P < 0.001) and in elastic modulus (E-modulus) between the low BMD group and the two higher groups (P < 0.001). A high correlation between both intrinsic and extrinsic measures of bone strength and BMD was thus demonstrated. The projected change in each of the variables reported, for a 0.1 g/cm² alteration in BMD (within the BMD range evaluated in this study) is as follows, maximum load 708 N; stress at maximum load 50 N/mm²; stiffness 391.6 N/mm and E-modulus 108 N/mm² (P < 0.001). The results confirm the relationship between BMD and bone strength and indicate that BMD screening can be used in fracture risk assessments in production pigs.

Key Words: Bone mineral density, Pigs, Three point bending test