Abstract
BackgroundHueter-Volkmann's law regarding growth modulation suggests that increased pressure on the end plate of bone retards the growth (Hueter) and conversely, reduced pressure accelerates the growth (Volkmann). Literature described the same principle in Rat-tail model. Human spine and its deformity i.e. scoliosis has also same kind of pattern during the growth period which causes wedging in disc or vertebral body.MethodsThis cross sectional study in 150 patients of adolescent idiopathic scoliosis was done to evaluate vertebral body and disc wedging in scoliosis and to compare the extent of differential wedging of body and disc, in thoracic and lumbar area. We measured wedging of vertebral bodies and discs, along with two adjacent vertebrae and disc, above and below the apex and evaluated them according to severity of curve (curve < 30° and curve > 30°) to find the relationship of vertebral body or disc wedging with scoliosis in thoracic and lumbar spine. We also compared the wedging and rotations of vertebrae.ResultsIn both thoracic and lumbar curves, we found that greater the degree of scoliosis, greater the wedging in both disc and body and the degree of wedging was more at apex supporting the theory of growth retardation in stress concentration area. However, the degree of wedging in vertebral body is more than the disc in thoracic spine while the wedging was more in disc than body in lumbar spine. On comparing the wedging with the rotation, we did not find any significant relationship suggesting that it has no relation with rotation.ConclusionFrom our study, we can conclude that wedging in disc and body are increasing with progression on scoliosis and maximum at apex; however there is differential wedging of body and disc, in thoracic and lumbar area, that is vertebral body wedging is more profound in thoracic area while disc wedging is more profound in lumbar area which possibly form 'vicious cycle' by asymmetric loading to spine for the progression of curve.
Highlights
Hueter-Volkmann's law regarding growth modulation suggests that increased pressure on the end plate of bone retards the growth (Hueter) and reduced pressure accelerates the growth (Volkmann)
We have commonly observed that proportion of vertebral wedging in lumbar spine is minimal even in acute curves when it is compared with thoracic spine
Stokes and Aronsson [11] have shown that in idiopathic or neuromuscular scoliosis, disc wedging is higher in thoracic region and vertebral body wedging is higher in lumbar or thoraco-lumbar level; and suggested importance of anatomic region for the proportion of wedging
Summary
Hueter-Volkmann's law regarding growth modulation suggests that increased pressure on the end plate of bone retards the growth (Hueter) and reduced pressure accelerates the growth (Volkmann). Roaf [13] has proposed a vicious cycle for progression of kyphosis Based on this law, we have commonly observed that proportion of vertebral wedging in lumbar spine is minimal even in acute curves when it is compared with thoracic spine. We measured wedging of vertebra and disc in thoracic and lumbar spine in a large sample with adolescent idiopathic scoliosis, and compared them to know whether the wedging, if found, was significant This indicates that if wedging increases with increase curve, it causes stress concentration and growth modulation causing the progression of curve. The main goals of this paper are 1) to study the difference in the wedging of disc and vertebral body between thoracic and lumbar spine, and 2) to compare the amount of wedging according to severity of the scoliosis curve
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