[Upright posture impact on spine susceptibility in scoliosis and progression patterns of scoliotic curve].

OBJECTIVE

To investigate the impact of upright posture on spine susceptibility in scoliosis and scoliotic curve progression patterns.

METHODS

There were 3 groups designed in the experiment: bipedal rats group (n = 26), quadrupedal rats group (n = 26) and sham operation bipedal control (n = 12). Taking the advantage of bipedal rats' upright-posture simulating effect, operations were exerted with posterior central approach between scapulas. Along the spatial of erector spinae muscle and trunk muscles, left side upper (T2-3 or T3-4) and lower (T10-11 or 11 - 12) ribs were tethered with type4 thread to make asymmetrical stress and simulate a primary thoracic curve. At time of 1, 2, 3, 4, 6 and 8 weeks post-operation (PO), each group were taken dorsoventral X-ray photographs for dynamic observation on the difference of scoliosis turnover and to compare the curvature progression difference between bipedal and quadrupedal rats.

RESULTS

Operation resulted in a primary single thoracic curve or thoracolumbar curve convex to the right in both bipedal and quadrupedal rats. At 1 - 4 weeks PO, all asymmetrical tethers became loose because of rib fracture or osteolysis at the tether sites. All scoliosis of quadrupedal rats disappeared and spine resume straight in 1 - 4 weeks later. Analogically, scoliosis disappeared in bipedal rats for those tethers loose in 1 w PO. But prolonged tethering, scoliosis progression rates increased conspicuously. 3 - 4 weeks' tether time led to irreversible scoliosis. Meanwhile, the curvature progression patterns of bipedal rats presented to be various, including the stable single thoracic curve, progressive thoracolumbar single curve and progressive double curve. These curvatures were much alike that of human idiopathic scoliosis. No scoliosis appeared in sham operation bipedal control.

CONCLUSIONS

The upright posture increased spinal susceptibility in scoliosis; Upright posture changes the progression pattern of scoliosis, leading to variegated scoliotic morphouses during primary thoracic curve progression, while inducing curve compensation phenomenon in scoliosis.