Abstract
BackgroundAn association between adolescent idiopathic scoliosis and osteopenia has been proposed to exist. It is still not clear whether there is such an association and if so, whether osteopenia is a causative factor or a consequence. Our previous pilot studies have suggested the presence of osteopenia in scoliotic animals. The aim of this study was to investigate the development of scoliosis in an unpinealectomized bipedal osteopenic rat model, implementing osteoporosis as a causative factor.MethodsFifty Sprague-Dawley rats were rendered bipedal at the 3rd postnatal week and separated into control (25 rats) and heparin (25 rats receiving 1 IU/gr body weight/day) groups. DEXA scans after 4 weeks of heparin administration showed low bone mass in the heparin group. Anteroposterior and lateral x-rays of the surviving 42 animals (19 in heparin and 23 in control groups) were taken under anesthesia at the 40th week to evaluate for spinal deformity. Additional histomorphometric analysis was done on spine specimens to confirm the low bone mass in heparin receiving animals. Results of the DEXA scans, histomorphometric analysis and radiological data were compared between the groups.ResultsBone mineral densities of rats in the heparin group were significantly lower than the control group as evidenced by both the DEXA scans and histomorphometric analyses. However, the incidence of scoliosis (82% in heparin and 65% in control; p > 0.05) as well as the curve magnitudes (12.1 ± 3.8 in heparin versus 10.1 ± 4.3 degrees in control; p > 0.05) were not significantly different. Osteopenic rats were significantly less kyphotic compared to control specimens (p = 0.001).ConclusionsThis study has revealed two important findings. One is that bipedality (in the absence of pinealectomy) by itself may be a cause of scoliosis in this animal model. Further studies on animal models need to consider bipedality as an independent factor. Secondly, relative hypokyphosis in osteopenic animals may have important implications. The absence of sagittal plane analyses in previous studies makes comparison impossible, but nonetheless these findings suggest that osteopenia may be important in the development of 3D deformity in adolescent idiopathic scoliosis.
Highlights
An association between adolescent idiopathic scoliosis and osteopenia has been proposed to exist
Nineteen rats in the heparin group and 23 rats in the control group were available for evaluation at the end of the study
Average coronal curve magnitude was 12.1 ± 3.8 degrees in the heparin group whereas the control group was observed to be at 10.1 ± 4.3 degrees (Table 3) (p > 0.05)
Summary
An association between adolescent idiopathic scoliosis and osteopenia has been proposed to exist. Sadat Ali et al compared bone densities of girls with idiopathic scoliosis with their normal siblings and found significant differences [10] It is not clear whether this finding is a cause or a result of the deformity. Another report by Cheng et al indicated that children with idiopathic scoliosis had lower bone density, but the density did not correlate with the type or severity of the curves [11]. This finding may indicate that osteopenia is a causative factor rather than the result of the condition
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