Radiologic and histological observations in experimental T1-T12 dorsal arthrodesis: A qualitative description of T1-T12 segment and other body parts involved, between prepubertal age and skeletal maturityxs

Abstract

Background: This experimental study provides a qualitative description and the morpho-structural features of the fusions taking place in the thoracic spine between prepubertal age and skeletal maturity. There is a lack of informations regarding the influence of partial or total dorso-thoracic vertebral arthrodesis on the development of the thoracic cage as well as its potential effects on different intra and extra-thoracic organs. This study admits the hypothesis that vertebral arthrodesis may have influence on other body areas and so, it intends to verify the possible secondary involvement of other body parts, such as intervertebral discs, cervical and thoracic spinal ganglia, sternocostal cartilage, ovaries and lungs.

Materials and methods: Fifty-four female New Zealand white rabbits were submitted to dorsal arthrodesis. The radiologic imaging and light microscopy histological pictures were taken and studied in all. Computed tomography (CT) scan measurements were performed in operated and sham operated rabbits at different time. Similarly, histological specimens of intervertebral discs, cervical and thoracic spinal ganglia, sternocostal cartilage, ovaries and lungs were analyzed at different times. The study ended at the age of 17-18 months.

Results: Most rabbits had formed a fusion mass, which was only fibrous at first, then osteofibrous and finally, in the older subjects, structured in lamellar-osteon tissue. Intervertebral foramens were negatively involved in vertebral arthrodesis, as shown by CT scans. Intervertebral discs showed irregular aspects. The increase of atresic follicles and the reduction of primordial follicles in operated rabbits led to the hypothesis of a cause-effect relationship between arthrodesis and modified hormonal status. Dorsal root ganglia showed microscopic alterations in operated rabbits especially.

Conclusions: The process of fusion mass and bone formation, associated with the arthrodesis, involves at different degrees of the vertebral bodies, discs and intervertebral foramens, ganglia and spinal nerve roots.

Keywords: Computed tomography scan images; Spinal column; arthrodesis; computed tomography scanners; dorsal arthrodesis; histology; histopathology; prepubertal rabbits; qualitative study; rabbits.

Figure 1

Computed tomography scan three-dimensional maximum intensity projection images of the thoracic area of the spine of a control rabbit; dorsal view on the left (a) and lateral view on the right (b). Rabbit submitted to dorsal vertebral arthrodesis with view of the metal rods implanted; computed tomography scan images (c and d)

Figure 2

Three-dimensional computed tomography volume rendering reconstruction of sham operated rabbit (a) and operated rabbit (b) More clearly showing the presence of a reactive osteofibrous layer, covering the metal rods (arrows)

Figure 3

T1–T12 sagittal computed tomography scan reconstructions at t1–t4 showing intervertebral bone fusion. Sagittal computed tomography scan reconstruction on the left (a-c) and three-dimensional-maximum intensity projection on the right (d and e): Spaces occupied by intervertebral discs are clearly visible (d); Different view of the intervertebral foramen profile in sham operated rabbits (d) and rabbits submitted to arthrodesis (e)

Figure 4

Morpho-structural details of the osteofibrous layer and the vertebral body (a-c), Displaying osteocartilagineous trabeculae and osteoblastic activity (c, arrows). Development of osteofibrous layer: From fibrous and bone-fibrous structure (d and e) to bone structure (f); Connection between the lower part of the bone layer and the underlying vertebral bone trabeculae (f, arrows). H and E, ×10, ×20 and × 40 light microscopy magnification

Figure 5

Linear or irregular shape of vertebral cartilage in sham rabbits (a) and rabbits submitted to arthrodesis (b and c). Morpho-structural details of the intervertebral disc: Fibrous part (d) and nucleus pulposus, partially misshaped as a consequence of arthrodesis surgery (e). H and E, ×10 and × 20 light microscopy magnification

Figure 6

Areas of calcification (a) and asbest-like degeneration (b) of costal cartilage in rabbits submitted to arthrodesis. H and E, ×20 light microscopy magnification

Figure 7

Noncavitary ovarian follicles in 6–8-week-old prepubertal female rabbits (a and b). Normal ovarian follicles at various stages of development (c), Atretic follicles and corpus albicans (d). Reserves of ovarian follicles in sham rabbits (e) and rabbits submitted to arthrodesis (f). H and E, ×10 and × 20 light microscopy magnification

Figure 8

Morpho-structural details of central and peripheral nervous system: Motor neurons of anterior horns of the spinal cord and Nissl substance (a) dorsal root ganglion neurons of sham rabbits (b) and rabbits submitted to arthrodesis (c-e). Dorsal root ganglion neuron details (c-e) of neuronal characterization 1 and 2, as in text. H and E, ×10, ×20 and × 40 light microscopy magnification