Flat-back syndrome is the loss of lumbar lordosis of the spine after one has Scoliosis surgery. The normal lumbar curvature becomes flat, or you may even get a reverse curvature (called lumbar kyphosis).
The condition is characterized by the inability to stand up straight, and typically patients will have back pain in their upper or lower spine. It can occur in patients of any age, but it is more likely to be found in older adults who have had Scoliosis surgery.
The most common cause is the use of distraction instrumentation such as a Harrington rod, in the lumbar spine. Obviously, the patients who have the most severe flat-back syndrome will be those who have had distraction instrumentation placed all the way down to the sacrum. Occasionally doctors will see patients who have thoracolumbar kyphosis-a deformity above the lumbar area which would aggravate the forward positioning of the spine and cause flat-back syndrome.
But far and away the most common etiological factor would be the use of distraction instrumentation in the lumbar spine.
Most-but not all-spine surgeons now know that this is something you don't do. In the early days of Scoliosis surgery, surgeons were more concerned with the frontal plane of the deformity and were not as aware of the sagittal or lateral plane, and over time they began to see patients presenting with these problems. It soon became apparent that the sagittal plane was just as important as the frontal, and they realized the importance of not using distraction instrumentation in the lumbar spine. As a result, the incidence of flat-back syndrome has diminished, but it is still seen.