Thoracic cage plasticity in prepubertal New Zealand white rabbits submitted to T1–T12 dorsal arthrodesis: computed tomography evaluation, echocardiographic assessment and cardio-pulmonary measurements

Abstract

Purpose We aimed to describe the morphological changes in the thoracic cage and spinal column induced in New Zealand White (NZW) prepubertal rabbits subjected to dorsal arthrodesis and observed at skeletal maturity by computed tomography (CT) scans. This was done to evaluate the plasticity of the thoracic cage of rabbits with non-deformed spine, by highlighting its modifications after spinal arthrodesis. Emogas data analysis, echocardiographic assessment and cardio-pulmonary measurements completed the evaluation.Methods Surgery was performed in 16 female rabbits, 6 weeks old. Nine were subjected to T1-T12 dorsal arthrodesis, while seven were sham-operated. Surgery involved the implant of two C-shaped stainless steel bars and heterologous bone graft. CT scans were performed before surgery, 2, 6 and 12 months after surgery. One week after the last CT scan, echocardiographic and emogas evaluations were performed. Results Chest depth (8 %), thoracic kyphosis (ThK) (23 %), dorsal and ventral length of the thoracic spine (11 %) and sternal length (7 %) were significantly reduced in operated compared to sham-operated rabbits. Mean values ± standard deviation (SD) of PaCO 2 , PaO 2 and sO 2 were not significantly different. Mean values ± SD of echocardiographic measurements were not significantly different between the two groups of rabbits, except for thickness of the interventricular septum in systole, contractile capacity of the left ventricle and ejection fraction. Conclusions T1-T12 dorsal arthrodesis in prepubertal NZW rabbits with non-deformed spine induced changes of the thoracic cage morphology. However, those changes are source of cardio-pulmonary complications not severe enough to reproduce a clinical picture comparable to thoracic insufficiency syndrome in humans.

Radiologic and histological observations in experimental T1–T12 dorsal arthrodesis

“…(a) The growth plate of the vertebral body, which stands as a critical aspect in the development of the vertebrae in arthrodesic situations (b) Regressive phenomena of costal cartilage, which represent possible limitating factors for the plasticity and flexibility of the entire thorax; 14 (c) Histopathological alterations of the ovaries following arthrodesis are possible (d) Spinal ganglia with pseudounipolar neurons and their SGCs, can be potential reactive centers related to back pain as they collect multiple, different peripheral afferent pathways. 35 36 37 …”

“…Rabbits were operated according to a modified “Wisconsin” technique or extra-canal dorsal T1–T12 vertebral arthrodesis, corresponding to posterior vertebral arthrodesis in bipeds, as punctually indicated in previous our works. 13 14 15 Multiple fragments of demineralized bone matrix (Grafton DBM, Osteotech Inc., Eatontown, NJ, USA) were applied, during the surgery, on each side of the spinous processes of the thoracic spine to favor fusion.…”

“…In the past, experimental studies in quadrupedal mammals showed that, when subjected to dorsal vertebral arthrodesis, such animals rarely develop scoliosis, while possible natural kyphosis is reduced. 11 12 It has then been shown experimentally in New Zealand white (NZW) rabbits that early partial or total dorso-thoracic vertebral arthrodesis affects the development of the rib cage and thoracic spine, it involves and alters vertebral values and ratios between thoracic diameters, 13 14 while it leaves the echocardiographic values unaltered and does not reveal significant disparity in the arterial blood gases of rabbits submitted to arthrodesis and sham operated rabbits; 15 other observations in dogs have reported thinning and disorganization of the growth plate. 16 17 …”

Evolution of casting techniques in early-onset and congenital scoliosis

“…These phenomena when properly matched, result in balanced appendicular and axial skeleton. 30,31 Changes in this phase of growth in spine lead to malformations. This results in disproportionate growth of axial and appendicular skeleton including chest wall hampering development of alveoli.…”

Changes in Thoracic Torsion in Adolescent Idiopathic Scoliosis Patients Within a 2-year Postoperative Period

“…The rib-vertebrae-sternum complex, which was first introduced as a concept in 2007 [2,5], exhibits a good 3D fit with the thoracic cavity and is usually visualized as an elastic structural model with an approximate cubic shape. Canavese et al evaluated the effects of vertebral growth disorders on the development of the ribs, sternum, and lungs, which form part of the rib-vertebral-sternal complex [6,7].…”