Validation of the sheep as a large animal model for the study of vertebral osteoporosis

Abstract

Rats have long been the animal of choice for research in the field of osteoporosis. In the search for a complementary large animal model the sheep appears useful but hitherto the extent of bone loss from the spine has failed to reach a level that is generally accepted as osteoporotic in humans. Osteoporosis was induced in ten sheep using ovariectomy, low calcium diet and steroid injection for 6 months. Bone samples of iliac crest (IC), lumbar spine (LS), and proximal femur (PF) from the osteoporotic sheep were compared with those from four normal sheep using densitometry, histomorphometry, biochemistry and basic mechanical testing. The differences were examined using an analysis of variance with Tukey-Kramer test. Overall, the bone mineral density at LS and PF decreased more than 25% after treatment. Trabecular bone volume decreased by 29.2, 33.4 and 42.6% in IC, LS and PF, respectively. The failure load of the LS in axial compression was reduced to 2,003 from 6,140 N. The extent of bone loss was sufficient to categorise these sheep as osteoporotic although the pattern of bone loss varied between sites. Reduced mechanical competence in LS confirmed the suitability of this model for evaluation of potential treatments for osteoporosis.

Osteoporose em caprinos

“…Os achados macroscópicos observados em todas as cabras foram semelhantes aos descritos na literatura (Jee & Yao 2001, Zarrinkalam et al 2009, Ding et al 2010. Os principais ossos afetados foram: úmero, rádio, fêmur, tíbia e corpos vertebrais.…”

“…No exame histopatológico, foram analisadas as extremidades proximais do úmero e tíbia, extremidades distais do rádio e fêmur e corpos vertebrais lombares onde foi observada diminuição do número e espessura das trabéculas ósseas, semelhante ao que é descrito na literatura em casos de osteoporose (Jee & Yao 2001, Zarrinkalam et al 2009, Ding et al 2010. Esses locais, com exceção das vértebras lombares, foram escolhidos, pois são locais de rápido crescimento ou movimento e indicados para análise quando se suspeita de doença óssea metabólica (Thompson 2007).…”

“…Braun et al (2009) recentemente relataram a primeira descrição de osteoporose espontânea em caprinos associada à deficiên-cia de cálcio e fósforo. Entretanto, há numerosas pesquisas sobre osteoporose que utilizam animais como modelo experimental, incluindo roedores, coelhos, cães, primatas (Jee & Yao 2001), ovinos (Zarrinkalam et al 2009, Ding et al 2010, Dvorak et al 2010, Veigel et al 2011) e caprinos (Li et al 2012).…”

Biomechanical and histological evaluation of an expandable pedicle screw in osteoporotic spine in sheep

“…Clinically, EPS should be inserted into the vertebra transpedicularly. Sheep spines have been accepted as a reasonable substitute for human spines [15,19,22,31,32,35,37] because their geometric properties are comparable to those of humans. Besides, sheep may be the biggest available animal model for spine surgery.…”

Motor control of lumbar instability following exposure to various cyclic load magnitudes

“…Smit [44] and Wilke et al [54,55] also validated the use of quadruped spine as an appropriate model for a human spine. Recently, the quadruped spine was also validated for vertebral osteoporosis [61]. Overall, neurophysiologically and biomechanically the quadruped spine is established as a valid model for spinal research with a size scaling for some mechanical data.…”