Unilateral enucleation affects the laterality but not the incidence of scoliosis in pinealectomized chicken.
METHODS
Randomized prospective study using an experimental scoliosis model in a pinealectomized chicken.


OBJECTIVE
To investigate the effect of the side of visual impairment on the incidence and laterality of the curves on a pinealectomized chicken model.


BACKGROUND
Visual impairment has been shown to increase the incidence of idiopathic-like scoliosis in human subjects when compared to the incidence of the general population. However, an association between the laterality of the visual impairment and incidence or laterality of scoliosis has not been established.


METHODS
A total of 60 newly hatched white leghorn chicks was divided equally into 3 study groups of no visual impairment (n = 20) (group 1), left-sided blindness by enucleation (n = 20) (group 2), and right-sided blindness (n = 20) (group 3). Pinealectomies and enucleations were performed on the second day after hatching. Anteroposterior radiographs were obtained at the 5th and 10th weeks, and the incidence, side, and magnitude of the resulting scoliotic curves were recorded.


RESULTS
The pinealectomy model yielded a general scoliosis incidence of 60%. The occurrence of scoliosis was not different among the groups (65%, 55%, 60%, respectively, P = 0.812). The incidences at the 5th and 10th weeks were both 40%, as a result of the death of 6 chickens between the 5th and 10th weeks, as well as the appearance or disappearance of curves during this time, again not different among the groups. However, the laterality of the curves was significantly different (P = 0.045). The visually impaired groups tended to have left thoracic curves as frequently as the right thoracic curves (7 right and 4 left in group 2, and 7 right and 6 left in group 3), whereas in group 1, the thoracic curves were predominantly right sided (12 right and 1 left). The average magnitude of the curves was 30.47 degrees +/- 19.32 degrees , not significantly different among the groups (27.6 degrees +/- 16.7 degrees , 23.7 degrees +/- 21.5 degrees , 39.8 degrees +/- 17.7 degrees , respectively, P = 0.109).


CONCLUSIONS
Unilateral visual impairment does not have a significant effect on the overall incidence and magnitude of scoliosis in the pinealectomized chicken. It does affect the laterality of the curves though, visually impaired subjects having a significantly higher likelihood of left thoracic curves, regardless of the side of blindness. It may be worthwhile to see if such an association is present in human beings as well.
Turhan
Egemen
E
Department of Orthopedics and Traumatology, Hacettepe University, Ankara, Turkey.
Acaroglu
Emre
E
Bozkurt
Gökhan
G
Alanay
Ahmet
A
Yazici
Muharrem
M
Surat
Adil
A
D000818:Animals; D002645:Chickens; D004195:Disease Models, Animal; D015353:Eye Enucleation; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D015994:Incidence; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D010870:Pineal Gland / Q000601:surgery*; D011446:Prospective Studies; D011859:Radiography; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging