Abstract 30

PINEALECTOMY AND SCOLIOSIS IN THE CHICKEN: MORPHOLOGICAL ASSESSMENT OF VERTEBRAL BODY DEFORMITY

NL Fazzalari ^1,2, R Davies ^1, IH Parkinson ^1,2, A Fagan ³

¹Bone & Joint Research Laboratory, Div of Tissue Path, IMVS and Hanson Institute, Adelaide, ²Dept of Path, ³Dept of Ortho & Trauma, Uni of Adelaide, Adelaide, SA, Australia.

Purpose of the study
Apical vertebral growth rate and final vertebral shape analyses were performed in a study of scoliosis in pinealectomized chickens.

Methods
Pinealectomy or a sham procedure was performed on two day old chickens. Survival was for two and four weeks postoperatively. Radiological and undecalcified histological examination of the apical vertebra of the resultant scoliotic deformity was performed. Growth rate was measured by means of fluorochrome labelling.

Results
A significantly smaller vertebral body cross sectional area was observed in birds with scoliosis when compared with those without a curve (5.9 ± 0.5 < 7.8 ± 2 [mm²], p < 0.002). The height of the apical vertebra in birds with scoliosis was greater than the equivalent vertebra in birds without scoliosis (6.7 ± 1.3 > 5.6 ± 1.1 [mm], p < 0.05).

These differences were visible by four weeks but were not apparent at 2 weeks of age.

Vertebral body wedging is reflected in the ratio of maximum to minimum vertebral body height in the coronal plane. This was apparent at four weeks (1.18 ± 0.07 > 1.04 ± 0.03, p < 0.001) but not at two weeks.

A growth rate asymmetry was suggested in the coronal and axial plane accounting for the resultant vertebral asymmetry.

Conclusions
We have shown that the apical vertebrae in this experimental model of scoliosis are longer and narrower than control vertebrae. The wedging of the apical vertebra may be accounted for by an asymmetrical growth rate in both the coronal and axial plane.

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