There have been many changes in the past 20 years in surgery to correct the sideways curvature of the spine called scoliosis. The standard operation up until the early 1980s used upright bars called Harrington rods. A rod was placed on both sides of the spine. Hooks were used to secure the rods to the bones.
Screws were later used in place of hooks in the low back to get better correction of lumbar curves. Recently some doctors in Germany found that screws can be used in the thoracic spine with good results. The thoracic spine is the middle portion of the spine from the base of the neck to the bottom of the rib cage.
Not only do the screws give a straighter spine, but they also hold the curve in place with less loss of correction. There are two possible reasons for this. One is that the screws give greater resistance to the force of tension on the spine. The second is that the screws are positioned in a different place than the hooks. This is thought to give them better leverage.
There are other reasons to use screws instead of hooks in scoliosis surgery for the thoracic spine. A shorter amount of the spine needs to be fused when using screws. There is generally also less blood loss during this surgery, and there are fewer problems after the operation.