Scoliosis 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, it is possible that 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
Management of scoliosis would try to compensate for this in the effort to stand up straight. As the person aged, there would be increased wear and tear, early-onset arthritis, disc degeneration, muscular stiffness, and pain with eventual reliance on painkillers, further surgery, inability to work full-time, and disability. "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