Abstract
Introduction
Melatonin-deficient rats are known to develop scoliosis when rendered bipedal. In a previous study we have shown that melatonin-deficient bipedal mice with scoliosis had lower bone density than did mice without scoliosis. Published work suggests that children with AIS have lower bone density than do healthy children. The aim of this study is to establish whether osteoporosis causes scoliosis. We hypothesised that bipedal rats with lower bone density would have increased spinal malalignment compared with the control group.
Methods
50 female Sprague-Dawley rats were rendered bipedal at 3 weeks of age by amputation of the forelimbs and tails. Two groups were formed: control group (n=25), in which rats received no drug; and the experiment group (n=25), in which rats received daily subcutaneous 1 U/g heparin injections. Animals were kept in standard cages, and food and water was provided at the top of the cages to encourage more time standing erect. DEXA scans were done on week 4 to assess bone density. Radiographs were taken on week 40 to assess spinal alignment in both control and experiment groups.
Results
19 rats in the heparin group and 23 rats in the control group were available for evaluation at the end of the study. At week 4, DEXA scans showed significant difference between the bone densities of the control and heparin groups (p<0·05), with the heparin group having lower bone density. The incidence of curves between the heparin and control groups were not statistically significant (p>0·01) (table). The magnitude of curves in scoliotic rats for the heparin group was 11·8° (SD 3·75) and for the control group 10° (4·3). The difference between the groups was not significant (p>0·05).
Conclusions
This study involved rats with normal melatonin levels and both groups showed a high frequency of scoliosis incidence. Although no significant differences were recorded between groups, the results suggest that bipedality is a cause for scoliosis, and low bone mineral density may further increase this tendency.
