Histological evaluation of the sheep's cervical spine segment 3/4--a histomorphological and histomorphometrical study

The 2-year-old sheep is a frequently used model in spinal orthopaedic research; however, so far no investigations have been performed on physiological tissue of untreated animals. In this study, the cervical spine segment 3/4 of eight 2-year-old female Merino sheep was evaluated histologically and histomorphometrically. Specimens were stained with Masson-Goldner-Trichrome, Safranin-Orange/Lightgreen, Safranin-Orange/von Kossa and Astrablue. Analysis of bone mass, mass of cartilage and mineralized cartilage in a defined region of interest was performed. A new finding of the study was that--although 2-year-old sheep is regarded as adult--tissue of the growth plate was still detected. Moreover, this study revealed that in the nucleus pulposus of the 2-year-old sheep notochordal cells are still existent, suggesting a complex remodelling of the nucleus pulposus in sheep.