Study Design. Dorsal arthrodesis of thoracic spine in a
prepubertal New Zealand White rabbit model.
Objective. Evaluating the consequences of dorsal arthrodesis
on the growth of the spine, sternum, and thorax
in prepubertal rabbits, through the study of CT scans.
Summary of Background Data. Vertebral arthrodesis
in the treatment of progressive idiopathic scoliosis in
prepubertal patients is not ideal, but is still a choice in
treating major deformities of the spine. Postoperative assessment
of spinal deformity is essential, feasible, and
recordable through CT scans.
Methods. Twelve female rabbits, 9 weeks old, were
subjected to surgery for dorsal arthrodesis of the upper
thoracic spine. Surgery involved the implant of 2 āCā-
shaped titanium bars, which were placed beside the spinous
processes of the thoracic vertebrae. Three CT scans
were performed, 10 (T1), 55 (T2), and 139 (T3) days after
surgery. Measures were obtained by Myrian Pro software
for 3 different groups: G1 with complete fusion, G2 with
incomplete fusion, and G3 sham-operated.
Results. The average of the dorsoventral/laterolateral
thoracic diameter ratio at fused levels is lower than 1 in G1
as well as in G2; on the contrary, in G3 is higher than 1. The
average growth of the sternum length between T1 and T2
and between T2 and T3 is minor in G1 than in G2 and G3.
The dorsal and ventral lengths of thoracic vertebral bodies
in the spinal segment D1-D6 is smaller in G1 and G2 than in
G3, whereas no differences were observed between the 3
groups in the D7-D12 segment without arthrodesis.
Conclusion. Dorsal arthrodesis in prepubertal rabbits
changes thoracic growth patterns. In operated rabbits, the
dorsoventral thoracic diameter grows more slowly than
the laterolateral thoracic diameter. The sternum as well as
the lengths of thoracic vertebral bodies in the spinal segment
D1-D6 grow less. The crankshaft phenomenon is
evident at the fused vertebral levels where there is a
reduction of thoracic kyphosis.