Effect of thoracic arthrodesis in prepubertal New Zealand white rabbits on cardio-pulmonary function

Abstract

Background:This experimental study was aimed at evaluating the type of cardiac and pulmonary involvement, in relation to changes of the thoracic spine and cage in prepubertal rabbits with nondeformed spine following dorsal arthrodesis. The hypothesis was that T1-T12 arthrodesis modified thoracic dimensions, but would not modify cardiopulmonary function once skeletal maturity was reached.Materials and Methods:The study was conducted in 16 female New Zealand White (NZW) rabbits. Nine rabbits were subjected to T1-T12 dorsal arthrodesis while seven were sham-operated. Echocardiographic images were obtained at 12 months after surgery and parameters for 2-dimensional and M-mode echocardiographic variables were assessed. One week before echocardiographic examination, blood samples were withdrawn from the animals’ central artery of the left ear to obtain blood gas values. One week after echocardiographic assessment, a thoracic CT scan was performed under general anesthesia. Chest depth (CD) and width (CW), thoracic kyphosis (ThK) and sternal length (StL) were measured; thoracic index (ThI), expressed as CD/CW ratio. All subjects were euthanized after the CT scan. Heart and lungs were subsequently removed to measure weight and volume.Results:The values for 2-dimensional and M-mode echocardiographic variables were found to be uniformly and significantly higher, compared to those reported in anesthetized rabbits. CD, ThK, and StL were considerably lower in operated rabbits, as compared to the ones that were sham-operated. Similarly, the ThI was lower in operated rabbits than in sham-operated ones.Conclusion:Irregularities in thoracic cage growth resulting from thoracic spine arthrodesis did not alter blood and echocardiographic parameters in NZW rabbits.

Radiologic and histological observations in experimental T1–T12 dorsal arthrodesis

“…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 …”