Is decreased bone mineral density associated with development of scoliosis? A bipedal osteopenic rat model

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.

RETRACTED ARTICLE: Comparison of the sagittal profiles among thoracic idiopathic scoliosis patients with different Cobb angles and growth potentials

“…Idiopathic scoliosis is the most common spinal deformity in human, affecting more than 2% of the adolescent population and resulting in more than 600, 000 physician visits annually [ 1 ]. Recent studies have discovered several risk factors associated with progression to a severe curve, including the delayed age of first menstruation [ 2 ], lower bone age [ 3 ], high Cobb’s angle at presentation [ 4 ], and decreased bone density [ 5 ]. In addition, some scholars report that there is a consistent loss of kyphosis in thoracic scoliosis patients compared with normal control or patients with thoracolumbar curves [ 6 , 7 ] and scoliosis progresses faster in patients with minor thoracic kyphosis [ 8 ].…”

Selective estrogen receptor modulation prevents scoliotic curve progression: radiologic and histomorphometric study on a bipedal C57Bl6 mice model

“…Although it was first assumed that this finding may be the consequence of a problem in the vitamin D synthesis or metabolism, no defects in this system or suggestive genetic polymorphisms could be identified [33,34]. In a study to clarify the role of osteopenia in scoliosis, Dede et al [35] demonstrated that there was no difference in rates of Fig. 4 Results of histomorphometric analysis.…”

Estrogen promotes the onset and development of idiopathic scoliosis via disproportionate endochondral ossification of the anterior and posterior column in a bipedal rat model

“…Therefore, we selected 5-week-old rats for the operation. At 5 weeks of age, all rats were rendered bipedal by amputating the forelimbs at a high humeral level and the tails at the root under anesthesia, as previously described 18 , 19 . After removing the forelimbs and tail, the bipedal rats were housed in special high cages with raised food and water to ensure that they maintained a standing posture most of the time; both food and water were gradually elevated in the cage as the bipedal rats grew.…”

“…Because the quadrupedal rodent spine is unlike the human spine and is not subjected to the same postural and dynamic mechanical forces required for the development of scoliosis 17 , bipedal rat and mouse models have been used to study the mechanism of AIS 18 , 19 . Therefore, in this study, an adolescent bipedal rat model was chosen to study the roles of estrogen in the onset and development of AIS.…”