Abstract 27

REGIONAL DIFFERENCES IN BONE MINERAL DENSITY LOSS IN RAT LUMBAR VERTEBRAE SIX-MONTHS POSTOVARIECTOMY

¹Rajaratnam R., Escott BG., Walsh W R

¹Surgical and Orthopaedic Research Laboratories, Prince of Wales Hospital, University of New South Wales, Sydney, NSW, Australia

Osteoporosis is a bone disease that affects the spine and hip in postmenopausal women. Technological improvements make it possible to gather detailed information to better understand this disease. This study aims to use DEXA and micro-ct to quantify regional variations in BMD throughout the individual lumbar vertebrae in ovariectomised rats.

Twenty-four female Sprague-Dawley rats were subjected to either bilateral OVX or sham surgery (n=12) at 10 weeks of age. Twenty-six weeks later the animals were sacrificed, lumbar spines were dissected out and cleared of soft tissue. All specimens were DEXA scanned, micro-ct and H&E stained. For DEXA, the ROI were limited to the cancellous vertebral body, and micro-ct was used to calculate BV/TV, Tb.Th and Tb.Sp.

The mean BMDs of each sham vertebral level were significantly higher (p<0.001) than the corresponding vertebral level in the OVX group. Furthermore, there were significant differences between different vertebral levels within each treatment group. Both the sham and OVX lumbar spines exhibit progressive increase in BMD from superior (L1) to inferior (L6) levels, with the sham BMD increasing more down the lumbar spine than the OVX BMD. This was confirmed in the micro-ct data in which there was a significant difference (p<0.01) in BV/TV, Tb.Sp and Tb.Th in the OVX lumbar spine between superior, mid and inferior regions.

DEXA and micro-ct enables in-depth analysis of the effects of osteoporosis on the lumbar spine in OVX rats. Both measurements confirmed the universal loss of BMD throughout the lumbar spine when compared to the sham rats.

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