Summary
The histomorphometrical cancellous bone parameters of osteoporotic ewes were examined
to establish a large animal model for the investigation of fracture treatment and
healing in osteoporotic bone. Eighteen animals were divided into 2 groups. Group 1
(n = 8, age 3 to 5 years) served as an untreated control. In Group 2 (n = 10, age
7 to 9 years) osteoporosis was induced by means of ovariectomy, methylprednisolone
application (average dose 160 mg/week) and Ca./Vit.D restricted diet during 7 months.
Biopsies from iliac crest, femoral head and lumbar spine were harvested. Structural
parameters from the biopsies were determined using μCT. In order to investigate static
and dynamic parameters of bone remodelling, undecalcified sections were digitized
and evaluated by means of image analysing software. Morphologically, bone area and
trabecular thickness were reduced in osteoporotic sheep. Bone perimeter (−20%), trabecular
number (−16%) and separation (+39%) showed a significant change in the iliac crest.
The structure model index indicated a shift from the plate-to the rodmodel. At different
skeletal sites of osteoporotic sheep bone resorption was significantly increased (250-675%),
and bone formation significantly decreased (77-89%). Osteoid thickness (O.Th) was
reduced (28-62%). In osteoporotic sheep the mean length of single labels was significantly
shortened (64-73%) and the mineralising surface showed a significant decrease (80-92%).
The mineralisation of the osteoid was comparable to the control group. The histomorphometrical
changes in this sheep model of osteoporosis are comparable to the human situation
of a combined post-menopausal and steroid-induced osteoporosis.
Keywords
Osteoporosis - animal model - sheep - histomorphometry - bone structure