In cases of scoliosis with fixed bony curves the same theory of corrective treatment cannot be applied as in cases of scoliosis with flexible curves. The fact that there is a fixed portion of the spine situated between two movable parts makes it easier to twist or displace the thorax as a whole than to make any change in the curved portion itself. As a result of this, forcible attempts to correct bony rotation in fixed curves will increase the lateral curve unless the thorax is kept from rotating, and forcible attempts to correct the lateral curve are likely to increase the rotation.
To judge from the observations on the cadaver, suspension as a corrective agent has but little corrective effects in rigid cases, being more likely to affect the compensatory curves than to produce any marked improvement in the rigid curve itself.
For the application of forcible jackets, the prone position, with the legs hanging perpendicularly, seems the most effective, for two reasons: First, because in the prone position greater side displacement between the vertebræ is permitted on manipulation than in the suspended position, because in the former the spine is not put on the stretch and part of its elasticity thereby exhausted; and, second, because in the prone position, with the legs hanging perpendicularly, it is possible to apply a jacket which shall flatten, in some degree, the lumbar curve of the spine, and when the erect position is assumed this flattening of the lumbar spine will necessitate some degree of hyperextension in the dorsal region on account of the equilibrium of the spine.
When the effect of rotations of the spine, in their effect on lateral deviation, is better understood it will probably be possible to add the element of rotation to the corrective force applied in the treatment of scoliosis.
With regard to forcible correction, one of two things may be done: (1) Force, carefully antagonized, may be applied to the curve itself, with a view to improving the curved portion of the spine; (2) the curved region may be twisted as a whole, or displaced sideways as a whole in its relation to the rest of the spine, as occurs when unopposed force is applied to the curve. The former is, of course, the more desirable when it is possible, but the latter may be of much use in improving the general outline of the body. The separation of the two is important for the application of intelligent therapeutic measures. It is relatively easy to displace the thorax in relation to the rest of the column, but relatively hard to change the curve itself.
Forcible correction seems to have its place only as preliminary to gymnastic treatment, and the writer would not wish to be understood to advocate the use of corrective plaster jackets except as a temporary means to secure a better foundation for better gymnastic or, if necessary, mechanical treatment.