The Harrington rod obviates the need for prolonged casting, allowing patients greater mobility in the postoperative period and significantly reducing the quality of life burden of fusion surgery. The Harrington rod was the precursor to most modern spinal instrumentation systems. A major shortcoming was that it failed to produce a posture wherein the skull would be in proper alignment with the pelvis, and it did not address rotational deformity. As the person aged, there would be increased wear and tear, early onset arthritis, disc degeneration, muscular stiffness, and acute pain. "Flatback" became the medical name for a related complication, especially for those who had lumbar scoliosis.In the 1960s, the gold standard for idiopathic scoliosis was a posterior approach using a single Harrington rod. Post-operative recovery involved bed rest, casts, and braces. Poor results became apparent over time.In the 1970s, an improved technique was developed using two rods and wires attached at each level of the spine. This segmented instrumentation system allowed patients to become mobile soon after surgery.In the 1980s, Cotrel-Dubousset instrumentation improved fixation and addressed sagittal imbalance and rotational defects unresolved by the Harrington rod system. This technique used multiple hooks with rods to give stronger fixation in three dimensions, usually eliminating the need for postoperative bracing. Evolution
There are links between human spinal morphology, bipedality, and scoliosis which suggest an evolutionary basis for the condition. Scoliosis has not been found in chimpanzees or gorillas. Thus, it has been hypothesized that scoliosis may actually be related to humans morphological differences from these apes.
Other apes have a shorter and less mobile lower spine than humans. Some of the lumbar vertebrae in Pan are "captured", meaning that they are held fast between the ilium bones of the pelvis. Compared to humans, Old World monkeys have far larger erector spinae muscles, which are the muscles which hold the spine steady. These factors make the lumbar spine of most primates less flexible and far less likely to deviate than those of humans. While this may explicitly relate only to lumbar scolioses, small imbalances in the lumbar spine could precipitate thoracic problems as well.Scoliosis may be a byproduct of strong selection for bipedalism. For a bipedal stance, a highly mobile, elongated lower spine is very beneficial. For instance, the human spine takes on an S-shaped curve with lumbar lordosis, which allows for better balance and support of an upright trunk. Selection for bipedality was likely strong enough to justify the maintenance of such a disorder. Bipedality is hypothesized to have emerged for a variety of different reasons, many of which would have certainly conferred fitness advantages. It may increase viewing distance, which can be beneficial in hunting and foraging as well as protection from predators or other humans; it makes long-distance travel more efficient for foraging or hunting; and it facilitates terrestrial feeding from grasses, trees, and bushes.