The effect of pinealectomy on scoliosis development in young nonhuman primates.
METHODS
Prospective study on pinealectomy in primates.


OBJECTIVE
To evaluate whether pinealectomy in a bipedal nonhuman primate model will result in the development of scoliosis.


BACKGROUND
Pinealectomy in newborn chickens consistently resulted in scoliosis development. Published data suggest that the surgical removal of the pineal, loss of melatonin secretion, and a bipedal posture are important elements in the development of scoliosis in lower animal models.


METHODS
There were 18 rhesus monkeys between 8 and 11 months old that underwent pineal excision. All monkeys were kept in a regulated 12-hour light-dark cycle. Monthly radiographs assessed scoliosis development. Completeness of pineal excision was assessed by measurement of a major metabolite of melatonin in the urine, 6-sulfatoxymelatonin, using an enzyme-linked immunosorbent assay assessed.


RESULTS
Mean follow-up was 28 months (range 10-41). Seven monkeys died prematurely, and 11 survived to date; the data from those that died could still be used, although follow-up was shortened. At the latest follow-up or death, scoliosis did not develop in any of the monkeys. Urinary 6-sulfatoxymelatonin measurements revealed 3 patterns. Group 1 consisted of 10 monkeys, which showed definite evidence of complete pineal excision. Group 2 consisted of an uncertain group of 2 monkeys in which the nighttime melatonin level is slightly high. Group 3 consisted of 6 monkeys that had incomplete pineal excision or ectopic melatonin production.


CONCLUSIONS
To our knowledge, this is the first report of pinealectomy in nonhuman primates. Of the 18 monkeys, 10 had a loss of melatonin secretion, for a mean of 29 months after surgery. Because none of the monkeys had scoliosis develop, this study strongly suggests that the possible etiologic factors producing idiopathic scoliosis in lower animals are different from primates, and findings in lower animals cannot necessarily be extrapolated to human beings.
Cheung
Kenneth M C
KM
Department of Orthopaedics and Traumatology, University of Hong Kong, Hong Kong, China. cheungmc@hku.hk
Wang
Ting
T
Poon
Angela M S
AM
Carl
Allen
A
Tranmer
Bruce
B
Hu
YouGu
Y
Luk
Keith D K
KD
Leong
John C Y
JC
D000818:Animals; D002940:Circadian Rhythm; D008253:Macaca mulatta; D008550:Melatonin / Q000378:metabolism; D019635:Neurosurgical Procedures / Q000009:adverse effects*; D010870:Pineal Gland / Q000601:surgery*; D011184:Postoperative Period; D011859:Radiography; D012600:Scoliosis / Q000209:etiology*; D013131:Spine / Q000000981:diagnostic imaging; D013997:Time Factors
D008550:Melatonin