But Chang has gone much further in improving the pedicle screw technique. Whereas implanting pins in the thoracic vertebrae doesn't have much impact on daily life, placing them in the lumbar vertebrae causes the latter to lose their flexibility, so that it becomes impossible to bend or turn at the waist. This causes much inconvenience in daily life, not to mention completely ruling out activities like cycling and yoga.
問題是，將鋼釘植入後背胸椎，對日常活動不會有太大影響，但若是植入人體活動的樞紐──腰椎後，被固定的腰椎將失去柔軟性，無法彎腰、轉腰，生活依然不便，更別提有很多運動如騎自行車、瑜珈都不能作。