Abstract 5

OSTEOPOROTIC SHEEP AND BALLOON KYPHOPLASTY

Beard H^¹, Schultz CG², Moore RJ^1,3

The Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science^¹; Department of Nuclear Medicine and Bone Densitometry, Royal Adelaide Hospital²; Department of Pathology, University of Adelaide³, Adelaide, South Australia.

Balloon kyphoplasty is a novel procedure that aims to restore vertebral body height by injecting cement into a formed cavity. The aim of this study was to assess the potential of an osteoporotic sheep model for kyphoplasty.

Ten lactating ewes (mean age 8 years) were ovariectomised, injected weekly with dexamethasone (Dexafort, Intervet, Australia) and fed low calcium diet for up to six months and compared with non-ovariectomised and non-treated controls. Dual-energy X-ray absorptiometry (DXA) was used to assess bone mineral density (BMD) in the lumbar spine. Sheep were euthanased at intervals and the entire lumbar spine processed for histology, quantitative histomorphometry and micro-CT (computed tomography). Inflation of a balloon tamp (Kyphon Inc. USA) was attempted ex vivo in a vertebral body.

After 6 months BMD decreased significantly (p<0.05) by 29.5±6.5%, trabecular bone volume (L2- L4) decreased from 29.12±1.56% to 20.18±0.51% and trabecular thickness decreased from 0.15±0.01mm to 0.09±0.00mm. A balloon tamp was inflated successfully in a vertebral body.

Using DXA and cancellous bone histomorphometry this study has demonstrated significant bone loss in the sheep lumbar spine up to 6 months after ovariectomy and continuous steroid treatment. The successful inflation of a balloon tamp augers well for kyphoplasty studies in this model.

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